CN1981411A - Improvements to articles comprising optical fibers having fiber Bragg gratings and methods of making said articles - Google Patents

Abstract

The invention relates to an article comprising a length of optical fibre comprising a fibre Bragg grating dispersed over a FBG-section in the length of optical fibre, and a package comprising a carrier having a carrier surface for supporting at least a supported portion of the optical fibre comprising the FBG-section. The invention further relates to a device comprising said article, to the use of said article and to a method for producing the same. It is an object of the present invention to seek to provide an optimal (e.g. elongated) package having a relatively low sensitivity to mechanical vibrations from the environment. This object is achieved if the surface of the carrier for supporting the optical fiber comprising the fiber Bragg grating is convex in the longitudinal direction of the optical fiber during use of the article. This has the advantage of attenuating the effect of vibrations from the sound source (or other mechanical vibration source) in an environment comparable to prior art solutions. In one embodiment, the carrier comprises two different materials, each adapted for specific tuning of the wavelength selected by the fiber Bragg grating. The present invention is applicable, for example, to a fiber laser for sensing, to (a low-frequency/low-phase noise fiber laser) a fiber laser for wavelength tuning, and to a package of a fiber laser.

Description

Improvements to articles comprising optical fibers having fiber Bragg gratings and methods of making said articles

technical field

The present invention relates to the packaging of optically active optical fibers including fiber Bragg gratings, such as fiber lasers, and in particular to placing the optical fibers in the package so that the susceptibility to mechanical vibrations is minimized. The invention further relates to tuning the wavelength selectivity of fiber Bragg gratings, such as tuning the laser wavelength of a fiber laser.

In particular, the invention relates to an article comprising a length of optical fiber for a laser, the optical fiber including fiber Bragg gratings on top of FBG segments dispersed in the length of optical fiber, and a package. In addition, the invention relates to a device comprising such an article, the use of said article and a method for its production.

The invention can be used, for example, in fiber lasers for sensing, in wavelength tunable fiber lasers (low frequency/phase noise fiber lasers) and in fiber laser packaging.

Background technique

The following description of the prior art relates to one of the fields of application of the present invention, fiber lasers comprising fiber Bragg gratings, eg fiber optic distributed Bragg reflectors (DBR) or distributed feedback (DFB) lasers.

Fiber lasers based on Bragg gratings such as DBR or DFB lasers are fiber lasers fabricated, for example, by UV writing of Bragg gratings into photosensitive optical fibers that have been doped with optically active agents such as rare earth ions such as erbium, Ytterbium and the like (see eg WO-98/36300). Typical dimensions of fiber lasers based on Bragg gratings are several millimeters to several centimeters along the fiber axis.

Fiber lasers based on Bragg gratings can combine attractive features such as stable single-mode operation, narrow linewidth and long coherence length, tunability, wavelength selection, mechanical robustness, small size, and low power consumption and insensitivity to electromagnetic interference (EMI).

For the vast majority of applications including, for example, wavelength tuning, Bragg grating-based fiber lasers are packaged under tension along their longitudinal direction, typically attached to a length-controllable, preferably relatively rigid, substrate. The mechanical properties of the substrate control the length of the fiber laser (and enable stabilization of the fiber optic medium) and thus the center wavelength of the fiber laser. The mechanical properties of the substrate mainly affect the environmental sensitivity of the laser.

For many applications it is desirable to further increase the coherence length or equivalently have low frequency and/or low phase noise.

The coherence length and frequency and phase noise performance of Bragg grating-based fiber lasers are negatively affected by environmental effects such as temperature and acoustic vibrations.

Temperature fluctuations cause changes in the refractive index through the thermo-optic effect. Bragg grating-based fiber lasers have a central wavelength temperature sensitivity of about 0.01 nm/°C in silica fibers with a thermo-optic coefficient of about 10 ⁻⁵ °C ⁻¹ . At 1550 nm, this corresponds to a frequency change of greater than 1 GHz/°C.

Although long-term temperature drifts can be compensated for by specialized packaging techniques involving structures with negative coefficients of thermal expansion as described in WO-99/27400, small and rapid temperature fluctuations are associated with increased linewidth or decreased coherence length The corresponding center frequency jitters.

Another important contribution to jitter and linewidth increase comes from acoustic perturbations (or generally mechanical vibrations). The linewidth and coherence length of lasers, including single-frequency rare-earth-doped fiber lasers, are ultimately determined by the optical spontaneous emission noise, which corresponds to the Shawlow-Townes limit. For rare earth-doped fiber lasers, it is in the Hertz region. In practice, however, environmental effects such as those mentioned above will affect cavity stability and lead to linewidths well above the Shawlow-Townes limit. For example, the thermo-optic effect will cause a frequency shift of 10 ^-5 ℃ ^-1 ·ν·ΔT[Hz], where ν is the optical frequency (in Hertz), and ΔT is the temperature change (in °C). As an example, if frequency stability better than 1 MHz at 1550 nm is required, the temperature fluctuation must be less than 10 ⁻³ °C (1 mK).

In order to stabilize the laser frequency and increase its coherence length, it is therefore necessary to protect it from environmental influences.

Frequency/phase noise reduction can be achieved by mounting the fiber laser on the neutral axis of the substrate. The neutral axis of the substrate is the unstrained axis under bending deformation conditions. In this way, if the substrate design is correct and the fiber laser is mounted on the neutral axis, the vibration excitation effect of the substrate on the fiber laser will be significantly reduced (see e.g. Hansen, L.V., "Constant Frequency Condition of Fiber Lasers in Strain", NSCM 15, Proceedings of the 15th Nordic Seminar on Computational Mechanics Conference, Eds.: Lund, E.; Olhoff, N.; Stegmann, J., pp.185-188, October 2002, Aalborg, Denmark, Hereinafter referred to as [LVH-2002]).

Substrates for fiber laser packaging can typically be elongated structures that can be considered as (mechanical) beams. The theory of the simply supported beam model used today was largely developed by Jacob Bernoulli and Euler in the eighteenth century. The deformation of the beam can be divided into three parts:

·Bending deformation

· Axial deformation, and

· Torsion deformation

For long beams with a large aspect ratio (ie, the ratio between length and section size), the deformation due to bending is at least greater in magnitude than axial and torsional deformations. Therefore, only the bend needs to be considered as the first order in the processing method to suppress the acoustic coupling. Under pure bending conditions, one side of the substrate will be in compression while the other side will be in tension. A neutral axis of zero deformation exists between these extremes. If the optical fiber is placed on this neutral axis, bending of the package has no effect: there is no strain on the fiber laser, so the frequency remains constant and noise from external vibrations is reduced. The exact position of the neutral axis within the substrate depends on the geometry of the section and is determined by the Bernoulli-Euler theory of simply supported beams (see e.g. J.M.Gere and S.P.Timoshenko, "Mechanics of Materials", Fourth SI Edition, Stanley Thornes ( Publishers) Ltd., 1999, section "Location of the Neutral Axis" on pp. 311-312, referred to elsewhere in this application as [Timoshenko]). The theory places the neutral axis at the point where the first moment S of the cross-sectional area is zero:

s= _∫A y·dA=0

To this end, existing substrates/packages have been developed to reduce sensitivity to temperature changes and acoustic vibrations. This application relates to package design for attenuating the effects of acoustic vibrations. The temperature change is usually slow and thus controllable by means of heat source/heat sink elements.

Typically, the fiber is mounted under tension on the package, but is only secured (eg with adhesive) at each end of the laser (see eg WO-99/27400). Therefore, the central part of the fiber laser may have poor contact with the surface of the package due to the pre-strain of the fiber. This effect is shown in Figure 2.b. This effect is undesirable where the laser is placed along the neutral axis of the package. In this case, detachment will lead to a shortening of the laser cavity length and/or grating period and thus a change in the lasing frequency.

However, securing an optical fiber including a fiber Bragg grating to the neutral axis of the package without changing the properties of the fiber can be problematic. Using adhesive to fix the grating along the length of the fiber can damage the fine Bragg gratings in the fiber core due to uneven curing of the adhesive. The adhesive curing process creates a strain field in the fiber. Said inhomogeneous strain field destroys the periodicity of the Bragg gratings and the article from which it is formed, such as a fiber laser, no longer functions as intended.

It is therefore of interest to provide a solution for assembling optical fibers (eg including fiber lasers) into packages which overcomes the above problems.

As discussed above, of the three modes of deformation of the simply supported beam (ie bending deformation, axial deformation and torsional deformation), only bending needs to be considered as the first order. However, there is a need to further improve the phase noise in fiber lasers to bring them up to the required standards in some demanding sensor applications such as those in noisy environments such as aircraft and ships. It is also necessary to include/reduce torsional deformation effects.

In some DFB fiber laser applications, frequency/wavelength tuning of the DFB fiber laser is required. Existing packages/substrates either utilize thermal expansion of the package or use a package design where the entire package is made of piezoelectric ceramic material. Since aluminum has a relatively large coefficient of thermal expansion (approximately 23*10 ^-6 °C ^-1 ), large wavelength tuning can be obtained by heating or cooling the aluminum package. However, the lasing frequency/wavelength can only be modulated slowly by thermal expansion. In some applications where fast modulation is required, piezoelectric ceramic materials can be used. When charged, very fast modulations (in the kilohertz region) are achievable with piezoceramic materials. However, only small frequency/wavelength changes are achievable compared to temperature tuning. When the whole package body is made of piezoelectric ceramic material, due to its relatively low coefficient of thermal expansion (approximately 1-5*10 ^-6 °C ^-1 ), only small thermal tuning can be obtained. Thus, there is a need for a package with improved tuning options.

A length of passive optical fiber with a diffraction grating accommodated in a curved groove of a support structure is described in US-4,795,226. The purpose of the assembly is to provide a suitable means of throwing away the controllable part of the fiber in the longitudinal direction. Polished fibers are used for devices that sense deformable variables in the fiber (ie the goal is to make the grating as sensitive as possible to vibrations from the environment).

US-6,240,220 describes a tunable fiber optic package comprising a curved support member for accommodating a passive fiber in a channel and for changing the tension within a fiber Bragg grating to a controlled The strain thus controls the piezoelectric section of the grating's characteristic wavelength. The function of the package is to change the wavelength response of the grating as needed. A relatively large tuning means that the support member has a small radius of curvature.

A device comprising a tunable fiber Bragg grating is described in US-2002/0131709. A passive fiber comprising a fiber Bragg grating is mounted on a substrate adapted to be bent by applying a force perpendicular to the length of the fiber, thereby increasing or decreasing the radius of curvature of the fiber comprising the grating , thereby tuning the grating wavelength. The object of the invention is to make the device as sensitive as possible to changes in the radius of curvature, thereby increasing the tuning range of the grating.

A package for a fiber laser is described in US-2002/0181908, wherein the fiber laser is housed in a tube of moderately rigid material that has been pre-shaped to fit in a suitably sized in the box. The ends are sealed with a suitable adhesive and the laser in the tube is positioned in a box surrounded by a curable adhesive.

Contents of the invention

This application is primarily concerned with aspects of bending and torsional deformations in articles comprising optical fibers with fiber Bragg gratings and corresponding carrier packages due to acoustic sources (or due to other mechanical vibrations, such as structural vibrations) - its purpose is to control the sensitivity of the article to said deformations. For typical applications of these articles, such as when fiber lasers are used to monitor acoustic phenomena (e.g. in the form of sensitive microphones), it is of interest to reduce the response of the article to noise from the environment in the 20Hz-20kHz range or at Sensitivity to 'non-signal' acoustic vibrations in the 'subsonic' range of 0.1-20 Hz. In other words, it is of interest to move the first resonant frequency of the package outside this (as above) range.

In this application, the terms 'resonant frequency', 'natural frequency' and 'eigenfrequency' are used interchangeably in relation to characteristic excitable vibrations of the carrier and package.

Generally, mechanical vibration can be divided into acoustic vibration and structural vibration. Acoustic vibrations may, for example, be airborne, structure-borne or subsea-borne. Non-acoustically induced structural vibrations typically have their origin in machines or engines. In this application relating to mechanical vibrations induced in articles comprising optical fibers with fiber Bragg gratings, the term 'acoustic vibrations' is used to cover all types of mechanical vibrations in the acoustic frequency range typically 0-20 kHz and the corresponding carrier package.

The present application relates to a fiber laser package with reduced sensitivity to mechanical vibrations, in which a fiber laser including a fiber Bragg grating is secured to a convex surface (at least over a portion of the fiber including the fiber Bragg grating). The sensitivity is further reduced by aligning the convex surface with the neutral axis of the fiber laser package. An example of such a package is a semicircular package with a cross-section with a U-shaped groove (Fig. 9.a and Fig. 3 such as Fig. h, the section shown in 3.i). However, curved packages are more difficult to produce than straight-sided packages and are used in a variety of applications (since these typically include support and optical and/or electrical connection systems or devices) planes of multiple parts). Elongated packages with straight-sided outer surfaces and a convexly curved laser carrier surface are also presented in this application (see Figure 8). The curved shape and precise position of the carrier surface on the package can be a target for optimization, which is the subject of this application.

It is an object of the present invention to provide an article comprising an optical fiber having a fiber Bragg grating and an encapsulation for carrying said optical fiber, said article having relatively low sensitivity to acoustic vibrations from the environment.

Another object of the present invention is to provide an article with relatively low sensitivity to bending deformations due to acoustic vibrations.

Another object of the present invention is to provide an article with relatively low sensitivity to torsional deformation due to acoustic vibrations.

It is also an object of the invention to provide a method for producing such an article.

Another object of the present invention is to provide a fiber laser with reduced phase noise.

Another object of the present invention is to provide a method of manufacturing such a fiber laser.

Another object of the invention is to provide a device comprising an article according to the invention and a use of the article according to the invention.

Another object of the present invention is to seek to provide an optimized package comprising an elongated carrier with a convex carrier surface for supporting an optical fiber comprising a fiber Bragg grating.

Another object of the invention is to seek to provide a package with improved tuning possibilities.

Other purposes appear elsewhere in the specification.

The objects of the invention are achieved by the embodiments of the invention described in the appended claims and in the following description.

Products:

The present invention provides an article comprising a length of optical fiber for a fiber laser and a package, the optical fiber including fiber Bragg gratings dispersed over FBG segments in the length of optical fiber, the package A carrier comprising a carrier surface adapted to support at least a supported portion of an optical fiber comprising an FBG section, the supported portion of the optical fiber being fitted on the carrier surface and secured to the optical fiber during use of the article on the carrier surface on each side of the FBG section to provide longitudinal tension in the supported portion of the optical fiber, and wherein the carrier surface is adapted to remain convex during use of the article.

The term 'article' in this application means a system or product or component. Articles comprising optical fibers with fiber Bragg gratings may comprise other parts to form optical systems, such as fiber laser products or systems comprising fiber lasers, and the like. On the other hand, the article may also only comprise an optical fiber with one or more Bragg gratings and its encapsulation.

The term 'optical fiber for fiber laser' means an optical fiber comprising an optically active region such as a region containing optically active ions such as rare earth ions such as Er, Yb, Dy, Tb, Tm, etc. Fiber Bragg gratings located in fiber lasers are more sensitive to mechanical vibrations from the environment than fiber Bragg gratings in passive fibers. Therefore, the problem of protecting an optical fiber for a fiber laser including in a package as the invention The subject of Fiber Bragg Gratings for immunity to acoustic noise from the environment.

In one embodiment, the supported portion of the optical fiber includes a fiber Bragg grating (ie, the FBG section of the optical fiber) and an optically active region. In one embodiment, a fiber Bragg grating forms part of the laser cavity together with the optically active region. In one embodiment, a Fiber Bragg Grating is located in the active region (ie the FBG section of the optical fiber includes a Fiber Bragg Grating and all or a portion of the optically active region). In one embodiment, the laser cavity comprises at least two fiber Bragg gratings spatially separated by an optically active region. In one embodiment, the laser cavity element is located in the supported portion of the optical fiber.

In one embodiment of the invention, a fiber Bragg grating is located outside the optically active region. In one embodiment, a fiber Bragg grating is located in an optically passive fiber (i.e., an optical fiber in which the concentration of optically active material below a level sufficient to amplify the optical signal). In one embodiment, the supported portion of the optical fiber comprises a length of optical fiber having an optically active region optically connected at both ends to a section of passive optical fiber, each section of passive optical fiber comprising a fiber Bragg grating assembled together to form DBR lasers.

The term 'encapsulation' in this application means a structural part allowing the handling of an article of which the optical fiber is a part, ie the enclosure comprises at least a carrier on which the optical fiber is supported or supported. The package may also include other components, such as temperature control devices (such as thermally tuned devices, including non-thermally tuned devices) or piezoelectric control devices, acoustic shielding devices for the package itself (such as including sound-absorbing materials), and the like. In one embodiment, the enclosure is adapted to minimize mechanical vibrations (eg acoustic vibrations) from the environment. Such changes may eg include the addition of sound absorbing material around the optical fiber in the package (see eg US-2002/0181908) and include features such as a carrier supporting the supported portion of the optical fiber as described hereinafter.

The term 'carrier surface adapted to support ... an optical fiber' means in this application that said surface is adapted or modified to support said optical fiber (e.g. by having an appropriate surface finish, friction, adhesion wait). The carrier may comprise a layer of another material than the carrier body so that the 'supported part of the optical fiber supported' actually has physical contact with said layer. In this case, a layer of material between the supported part of the supporting optical fiber and the carrier body is considered to be part of the carrier.

Supporting the supported portion of the optical fiber is secured to the carrier surface on each side of said FBG section in the optical fiber. This has the advantage of being able to control the physical path length of the enclosed portion of the optical fiber. The fixed optical fiber preferably extends over a length of optical fiber which is as short as possible, thereby securing the fixed fiber to the surface of the carrier. The fixing can be done by any conventional means such as adhesives, epoxies, welding, mechanical fixing and the like.

The supported portion of the optical fiber is mounted on the carrier surface to provide longitudinal tension within the optical fiber during use of the article. This has the advantage that physical contact between the closed portion of the optical fiber and the surface of the carrier is achieved in a simple and effective manner, thereby ensuring that the optical fiber and carrier are substantially unitary (including vibrating together). Another advantage resides in enabling specific differences in the coefficient of thermal expansion between the optical fiber and the carrier to be dealt with. A further advantage resides in improved heat dissipation from the optical fiber to the carrier at the end of the optical fiber.

In one embodiment, the length of the optical fiber between fixed points on the carrier surface is less than 50 cm, such as less than 20 cm, such as less than 10 cm, such as less than 5 cm, such as less than 2 cm, such as less than 1 cm. Alternatively, the length of the optical fiber between fixed points on the carrier surface may be longer (for example, by winding the optical fiber multiple times around a cylindrical support). However, a compromise can be made between optical performance and fiber length (material cost, volume occupied by the fiber, tolerances, etc.).

In one embodiment, the carrier surface is adapted to be fixed locally to the carrier surface (rather than to each side of the fiber Bragg grating as described above) avoiding the contact channel along the supported part of the optical fiber. This can be achieved by appropriate treatment of the surface of the carrier, eg ensuring a sufficiently low surface roughness (eg by polishing or laser ablation), applying lubricants, applying specific coatings to the surface, etc. In one embodiment, said carrier surface is adapted to ensure a substantially uniform axial strain in the supported portion of the optical fiber between fixed locations on the carrier surface.

The properties and physical implementation of Bragg gratings in optical fibers have been extensively described in eg WO-98/36300.

The term 'carrier surface adapted to remain convex' in this application means that the carrier surface supporting the optical fiber is convex in the longitudinal direction of the optical fiber, i.e. described by the carrier surface with a section along the length of the surface-adapting portion of the optical fiber Each point on the curved channel has a circle of curvature centered in the direction of the interior or body of the carrier (the channel is eg curved or circular eg circle, parabola or ellipse). Expressed in a different way: the curved path along the surface of the carrier at the (predetermined) point of contact with the supported part of the optical fiber is a continuous curve having the property that a straight line joining any two points on it is Extends into the interior of the carrier or body.

In a particular embodiment, the channel of physical contact between the supported portion of the optical fiber and the surface of the carrier supporting the optical fiber maintains a substantially constant shape and convexity during use of the article. Thus, the influence of mechanical vibrations caused by the environment on the characteristic wavelength of the fiber Bragg grating can be minimized.

It should be understood that the above definition envisages a certain 'macroscopic' degree of the carrier surface and the supported portion of the optical fiber ('macroscopic' being defined as ignoring unevenness on the carrier surface and fibers smaller than a certain size).

In a particular embodiment, the physical contact channel between the supported portion of the optical fiber and the surface of the carrier supporting the optical fiber is convex in the longitudinal direction of the optical fiber.

An advantage of the invention is that detachment of the supported portion of the optical fiber from the carrier surface is minimized if the optical fiber (eg in the form of a fiber laser) is placed on a surface that remains convex through the vibration cycle of the package. The surprising result is that the relatively small curvature (relatively large radius of curvature) of the contact channel between the carrier surface and the supported part of the optical fiber leads to a markedly reduced sensitivity to mechanical vibrations from the environment.

The term 'during use of the article' means in this application that in this application the article is specific, eg for a certain amplitude and frequency spectrum of ambient noise in a certain temperature range. In other words, the term 'the carrier surface remains convex during use' means that the carrier surface remains convex when deformed by specially designed vibrations.

In a particular embodiment, said carrier has at least one outer surface adapted to be fitted on a planar support. In one embodiment, the package has at least one outer surface adapted to be mounted on a planar support.

The advantage is that it facilitates assembling the article together and possibly connecting it to other optical, electronic and/or electro-optical components on a planar support, for example to form a module or system comprising said article.

The term 'adapted to be mounted on a planar support' means herein that the carrier can be mounted on standard supports used in the electronics and optics industry, for example in ceramic materials, polymer materials, metals including printed circuit boards. etc. on the substrate. Thereby, physical handling of the article is facilitated and signal connections to other components and systems are provided.

In a particular embodiment, said carrier is elongate. An elongated carrier means, for example, that the carrier has a spatial dimension that is greater than the other spatial dimensions, so that, for example, the carrier has a certain physical elongation in the direction of the supported portion of the optical fiber (after being assembled on the carrier surface ), the physical elongation is greater than its physical elongation in other directions (ie the support is 'beam-shaped').

The term 'substantially' is intended to mean substantially, but not necessarily entirely.

In one embodiment, the surface of the carrier is substantially semicircular when viewed in cross-section along the length of the supported portion of the optical fiber. This is advantageous in that it provides a simple and easy-to-manufacture carrier surface. The term 'carrier surface is substantially semicircular' means in this application that the curved path formed by the physical contact path between the supported portion of the optical fiber and the carrier surface along the length of the fiber is substantially semicircular ( That is to form a semicircle with a certain length and/or radial tolerance within ±20%, such as within ±10%, such as within ±5%.

In one embodiment, the physical contact channel between the supported portion of the optical fiber and the carrier surface along the length of the fiber is represented by a planar (convex) curve, eg a portion of a circle. Alternatively, however, it may form any other channel, such as a helical channel in one embodiment, wherein the supported portion of the optical fiber is wound helically on a cylindrical carrier surface.

In one embodiment, the carrier is symmetrical with respect to a plane spanned by the channel defined by the longitudinal extension of the optical fiber (i.e. for example by the carrier surface between the supported part of the optical fiber and the length of the optical fiber). The physical contact channel between them is defined).

In one embodiment, said carrier is a closed body, the surface of which remains convex during use of the article. The term 'closed body' refers to a cross-sectional view substantially along the length of the supported part of said optical fiber, the term 'closed body' in this application means solid (eg Figure 6 and Figure 9.a) or Hollow (eg Figure 5) bodies, as opposed to beam-shaped bodies (eg Figures 1, 2, 4, 9b, 10 and 11-14). This has the advantage of increasing the first fundamental resonance frequency compared to a corresponding 'hollow' or 'open' body (eg cylindrical with circular cross-section) or semi-circular (open, see Figure 4)).

The surface of the carrier - in a cross-sectional view along the length of the supported portion of the optical fiber - may follow any suitable (eg linear or convex) curved path adapted to the optical fiber and carrier (including its surface friction Force) material, fiber Bragg grating, characteristic wavelength, etc.

In one embodiment, the carrier surface is part of a cylindrical surface, preferably substantially with an elliptical or circular cross-section (see eg Fig. 5, 15) in the longitudinal direction of the supported part of the optical fiber. This has the advantage that a simple and easy-to-manufacture carrier surface is provided. It also has the advantage of providing a higher first fundamental resonant frequency than a corresponding 'open' body, while still avoiding detachment.

In a direction along the carrier surface perpendicular to the longitudinal direction of the supported portion of the optical fiber (i.e. perpendicular to the plane spanned by the physical contact channel between the supported portion of the optical fiber and the carrier surface along the length of the fiber), the carrier surface may Take any suitable shape, for example curved or linear. This includes the carrier surface with possible grooves formed in the carrier for mounting the optical fiber (see below, eg 361 in Fig. 3.b).

In one embodiment, said carrier (cylindrical such that the optical fiber is supported on the cylindrical surface) comprises a fully or partially through opening in the direction of an axis substantially parallel to the axis of the cylindrical carrier. A fully or partly through opening means here that, when assembled on the carrier, it traverses the carrier completely or partly in a section substantially in the longitudinal direction of the supported part of the optical fiber so that the supported part of the optical fiber is subjected to an annular structure (e.g. See Figure 5 or 11.a) for the opening of the support. Such a structure may be advantageous by saving material compared to a solid carrier. Additionally, the hollow portion of the enclosure may contain other components or structural components, thereby providing a compact system.

In one embodiment, said (possibly cylindrical) carrier surface is part of a solid encapsulation (i.e. does not comprise a through-opening in a section substantially in the longitudinal direction of the supported part of the optical fibre, see for example FIG. 6 .a, the example shown in 15.h). This has the advantage that a simple and easy-to-manufacture carrier surface is provided. This also has the advantage that a higher first fundamental resonance frequency is provided compared to a corresponding body with a through-opening.

In a particular embodiment of said article, the supported portion of the optical fiber is arranged substantially along the neutral axis of said encapsulation. This has the advantage of minimizing strain during package bending. In this way, the influence of the vibration excitation of the substrate on the fiber laser will be significantly weakened. Neutral curved channels for a given ontology can be found, for example, in J.M. Gere and S.P. Timoshenko, "Mechanics of Materials", Fourth SI Edition, Stanley Thornes (Publishers) Ltd., 1999, pp. 311-312, in Referred to elsewhere in this application as [Timoshenko].

In a particular embodiment of said article, the surface of the carrier for supporting at least the supported portion of the optical fiber is located in a groove in said carrier. This has the advantage of providing protection of the optical fiber and providing a suitable means for positioning the optical fiber along a predetermined curved path in the carrier body. It also has the advantage of enabling fixation in a direction perpendicular to the longitudinal axis of the optical fiber. In one embodiment, the groove comprises means for securing the optical fiber in the groove, for example in the form of one or more protrusions which locally narrow the groove to secure the optical fiber or in the form of a or a plurality of recesses that act as reservoirs for securing material such as adhesive or adhesive. In one embodiment, the local protrusions and/or recesses are spaced along the length of the trench for positioning the optical fiber in the trench. This ensures that the central axis of the optical fiber is along a specific path, such as the neutral path of the carrier (or package).

In a particular embodiment of said article, said grooves have a rectangular cross-section.

In a particular embodiment of said article, the cross-sectional shape of said groove is adapted to the cross-sectional shape of said supported portion of said optical fibre. This has the advantage that the optical fiber can be fitted easily and precisely (self-aligning) in the groove. Adaptation of the cross-sectional shape of the groove may include adjusting the shape of the groove (or a portion thereof, e.g. the bottom) to form a shape similar to the shape of the optical fiber (e.g. circular or oval, e.g. Fig. 3.b 361 in). However, the adaptation may also include adjusting the shape of the groove to form a shape different from the shape of the optical fiber (e.g. triangular or rectangular, e.g. Fig. 3.c), e.g. to facilitate alignment and/or Appropriate space is left around the fibers for the (fluid or solid) fill material.

In a particular embodiment of said article, said carrier has a substantially rectangular outer border when viewed in a section perpendicular to the longitudinal direction of said optical fiber when fitted in said groove. This has the advantage of providing a carrier with a relatively high ratio between the section torsion factor and the polar moment of inertia (K/J), thereby providing a carrier with a relatively high torsional natural frequency.

In a particular embodiment of said article, the supported portion of said optical fiber when situated on said carrier surface is completely or partially surrounded by a filling material based on said optical fiber having substantially the same dimensions. The supported portion of the optical fiber preferably has a mass density, such as within 100%, such as within 50%, such as within 30%, such as within 20%, such as within 10% of the mass density of the optical fiber. % within. This has the advantage that possible vibrations of the optical fiber acting on the trench walls are minimized. It also has the advantage that the optical fiber and the filling material are equivalent to one. It also has the advantage that the use of the filling material relaxes the requirements on the mechanical tolerances of the trench, since the filling material eliminates possible irregularities. It is also advantageous that the conditions for heat dissipation from the optical fiber can be improved (by using a thermally conductive filling material such as metal). In one embodiment, the filling material is a deformable material such as a thermal paste such as cooling paste, or a metal such as indium. In one embodiment, the filling material is fluid at least when it is applied to the trench. In one embodiment, the filling material is liquid at least when it is applied to the trench. In one embodiment, the filler material is hardened or cured after application, thereby increasing its viscosity.

In one embodiment, the filler material is Viton(R) (or hexafluoropropylene-vinylidene fluoride from Dupont-Dow Elastomers).

In a particular embodiment of said article, said carrier comprises a through opening in the longitudinal direction of the supported part of the optical fiber when assembled on said carrier, said supported part of the optical fiber being located therein (for example See Fig. 11.b, 11.c). An advantage of this is that it facilitates relatively high natural frequency package designs with improved stiffness and minimal deformation modes.

This has the advantage that the effect of torsional vibrations from sound sources (or other mechanical vibration sources) in the environment is reduced compared to prior art solutions (see eg Fig. 3.a). This also has the advantage of increasing the stiffness of the package, thereby increasing its first resonance frequency. Detachment is further reduced by confining the optical fiber in the longitudinal cavity in the form of a through-opening, thereby reducing the sensitivity to acoustic bending of the package.

In a particular embodiment of said article, said supported portion of said optical fiber is disposed substantially along a shear central channel of said encapsulation, thereby minimizing elongation of the optical fiber due to torsional deformation mode. When fitted in the through-opening, when viewed in a section perpendicular to the longitudinal direction of the optical fiber, if the package is doubly symmetric, i.e. has a center of shear coincident with the neutral axis for bending , then provides minimum elongation of the fiber when placed along the axis for the bending and torsional deformation modes.

In a particular embodiment of said article, said carrier comprises a plurality, preferably two, cooperating bodies which, when assembled together, provide said through-openings (see for example Fig. 3.c or 3.1 ). This has the advantage of combining the advantages of relatively high natural frequencies with improved stiffness and minimal deformation modes with the advantages of easy handling and assembly of optical fibers. In one embodiment, one of said bodies consists of a filler material. In one embodiment, the bodies are coupled by means of bonding material such as glue.

In a particular embodiment of said article, said through-opening has a cross-sectional shape adapted to the cross-sectional shape of said optical fiber.

The curvature of the carrier surface may preferably be optimized to minimize bending losses in the optical fiber and chirping in the fiber Bragg grating (the latter due to non-uniform deformation of the grating due to bending and friction of the grating, respectively. of).

In a particular embodiment of said article, the curvature of the curve defined by the contact channel of the supported part of said optical fiber with the carrier surface is in the range of 0.5 m ⁻¹ to 200 m ⁻¹ , for example at 1 m ⁻¹ In the range of to 200m ^-1 , for example in the range of 5m ^-1 to 70m ^-1 , for example in the range of 10m ^-1 to 50m ^-1 . In a particular embodiment of said article, said curvature is in the range of 0.004m ⁻¹ to 200m ⁻¹ , for example in the range of 0.004m ⁻¹ to 20m ⁻¹ , for example in the range of 0.004m ⁻¹ to 13m ^{−1 1} , for example in the range of 0.004m ^-1 to 5m ^- 1, for example in the range of 0.004m ^-1 to 2m ^-1 , for example in the range of 0.004m ^-1 to 1m ^-1 , for example in the range of 0.004 In the range of m ^-1 to 0.7m ^-1 , for example in the range of 0.004m ^-1 to 0.5m ^-1 , for example in the range of 0.1m ^-1 to 50m ^-1 , for example in the range of 0.2m ^-1 to 2m ^- 1 ¹ range.

In a particular embodiment of said article, said curvature is in the range of 0.1 m ⁻¹ to 1 m ⁻¹ .

In a particular embodiment of the article, the portion of the carrier surface supporting the optical fiber has an uneven surface comprising peaks or ridges and valleys or valleys, wherein when viewed in the longitudinal direction of the optical fiber , the distance between adjacent peaks or ridges is so small that the eigenfrequency of the optical fiber suspended between adjacent peaks or ridges is greater than 5 kHz, such as greater than 10 kHz, 20 kHz, such as greater than 25 kHz , such as greater than 30kHz. An example of an uneven surface may be a transition between surfaces of different materials, such as a multi-body carrier comprising an externally tunable material such as a piezoelectric material.

In this case, the term 'convex' should be understood as 'generally convex', since the curved path described by the surface-adapting portion of the optical fiber along the point of contact with the carrier surface is allowed to be segmented Linear (ie linear between actual physical contact points with the support surface, see 102 and 107 in Fig. 10.b).

In a particular embodiment of said article, the distance between adjacent peaks or ridges is less than 10 mm, such as less than 5 mm, such as less than 2 mm, such as less than 1 mm.

In one embodiment, the carrier surface and the surface-adapting portion of the optical fiber have substantially similar surface roughness (e.g. measured root mean square roughness (rms roughness) within a factor of 2, such as within a factor of 1.5, For example, the coefficient is within 1.2).

In one embodiment, aluminum is included in the substantial portion of the package volume responsible for the thermal expansion of the carrier surface. This has the advantage that it provides a heat-conducting carrier, a relatively cheap material and an attractive material for machining. In these embodiments, a material with a lower coefficient of thermal expansion, such as Invar(R), or a material with a coefficient of thermal expansion similar to that of the optical fiber is used in the carrier. In these embodiments, ceramic or piezoelectric materials may be used. By choosing the carrier material as the base material of the optical fiber (and possibly by including a certain prestraining of the optical fiber), possible differences in the temperature dependence of the corresponding thermal expansion coefficients can be taken into account, thus ensuring that during operation the Detachment does not occur within the predetermined temperature range. Greater stiffness of the carrier body (or rather, greater K/J, I/A and E/ρ ratios) (see equations (1a), (1b) and (1c) and as described below) is favorable.

Different materials are used in the package to achieve relatively slow and/or relatively fast tuning of wavelength ranges:

In a particular embodiment of said article, said carrier comprises at least two materials. An advantage of this is that the design flexibility is enhanced, ie it is advantageous to provide specific properties of the carrier and package (and thus the article).

In a particular embodiment, said carrier comprises at least one second body made of a material (designated Material-2, see below) whose longitudinal dimensions are specifically adapted for external modulation, for example by an external control signal. This has the advantage that it offers a possibility to dynamically influence the properties of the carrier and the encapsulation (and thus the article).

In a particular embodiment, said second body contains a material whose longitudinal dimensions are specifically adapted to allow electrical modulation. Electrical modulation is relatively easily provided eg as a direct or alternating voltage or current. It also has the advantage that it can be easily changed to a desired amplitude and/or repetition sequence or frequency. In a particular embodiment, said electrical modulation is voltage controlled with a frequency of less than 10 MHz, for example in the range of 0.1 Hz to 100 kHz, for example in the range of 20 Hz to 20 kHz. An advantage of this is that it provides a relatively fast modulation of the length of the carrier, thereby providing a means for controlling the phase and frequency of the laser.

In a particular embodiment, piezoelectric material is contained in said second body. This has the advantage that it provides a well-functioning means for dynamically changing the physical dimensions of the body. Alternatively, the second body may contain electrostrictive materials such as lead magnesium niobate (PMN) ceramic materials or magnetostrictive materials such as one or more lanthanides (rare earths) such as terbium and dysprosium plus iron alloy crystals)

In one embodiment, piezoelectric ceramic material is contained in the second body.

In a specific embodiment, the piezoelectric material is selected from the group of materials including piezoelectric ceramic materials such as polycrystalline ferroelectric ceramic materials, such as barium titanate and lead zirconate titanate (Pb) (PZT) and combinations thereof. Alternatively, natural materials such as quartz, calcium carbide, Rochelle, etc. can be used. However, the effect is relatively small in these materials. The aforementioned developed ceramic materials have superior properties compared to natural materials.

In a particular embodiment, said carrier comprises a first body made of a material (designated Material-1, see below) whose longitudinal dimensions are specifically adapted to undergo thermal modulation. This has the advantage that it offers the possibility to combine the modulating effect of the second body with the thermal tuning of the first body, wherein the material, volume, shape and position of the first and second bodies in the carrier are specifically adapted to The required tuning possibilities. Thermal improvement of the carrier can be provided, for example, by resistors or Peltier elements.

In one embodiment, the coefficient of thermal expansion α _T-1 of the material constituting said first body in the longitudinal direction of the carrier is substantially equal to the coefficient of thermal expansion α _T-2 of the material constituting said second body.

In a particular embodiment, the coefficient of thermal expansion α _T-1 of the material constituting said first body in the longitudinal direction of the carrier is substantially greater than the coefficient of thermal expansion α _T-2 of the material constituting said second body, for example greater than α 1.5 times _T-2 , such as greater than 2 times α _T-2 , such as greater than 5 times α _T-2 . This has the advantage of providing design parameters for optimizing tuning performance between relatively slow thermal tuning through the first body and relatively fast tuning through the second body.

In a particular embodiment, the first body comprises a material selected from the group of materials including metals such as aluminum or copper or alloys thereof, ceramic materials and combinations thereof. In one embodiment, the support material may comprise a material with a positive coefficient of thermal expansion (such as a metal such as aluminum or copper) or a material with a substantially zero coefficient of thermal expansion (such as Invar ^™ ) or a material with a negative coefficient of thermal expansion (such as ceramic material) or a combination thereof.

In a particular embodiment, said first body constitutes the main volume of said carrier.

In a particular embodiment, said second body or said second bodies are arranged asymmetrically with respect to a cross-section of the carrier perpendicular to its longitudinal direction at an intermediate position between the longitudinal ends of the carrier. In one embodiment, said second body has substantially the same cross-section as the remainder of said carrier, ie substantially continues the cross-section of the adjacent carrier section. This has the advantage that a direct mechanical connection to the optical fiber is provided. It also has the advantage of being a relatively simple mechanical solution with looser mechanical tolerances.

In a particular embodiment, said second body or said second bodies are arranged symmetrically with respect to a cross-section of the carrier perpendicular to its longitudinal direction at an intermediate position between the longitudinal ends of the carrier. This has the advantage that a symmetrical strain field is provided in the optical fiber. In one embodiment, the carrier comprises two first ones arranged symmetrically in the carrier and having substantially the same cross-section as the rest of the carrier, ie substantially continuing the cross-section of the adjacent carrier section. ontology. In a preferred embodiment, the two first bodies modulate synchronously.

It should be emphasized that the technical features related to carrier modulation and thus (e.g. in a laser) FBG tuning can be used for packages with a uniform carrier surface for supporting an optical fiber comprising a FBG (see e.g. FIG. 1 ) as well as for packages with convex Encapsulation on the surface of the carrier. Additionally, the structural features of the carrier having a cross-section perpendicular to the longitudinal direction of the optical fiber when mounted on the carrier may have any suitable form, including those shown in Figures 3a-3i.

Articles comprising fiber lasers or specified optical fibers

In one embodiment, said optical fiber and said fiber Bragg grating form part of said laser. Thereby a fiber laser is provided which is relatively less sensitive to acoustic vibrations from the environment, thus enabling the formation of lasers with relatively lower phase noise.

In a particular embodiment, said supported portion of the optical fiber comprises two spatially separated fiber Bragg gratings.

In a particular embodiment, said article comprises a DBR laser, wherein said optical fiber and said fiber Bragg grating form part of said DBR laser. Thereby a DBR fiber laser is provided which is relatively less sensitive to acoustic vibrations from the environment.

In a particular embodiment, said article comprises a DFB laser, wherein said optical fiber and said fiber Bragg grating form part of said DFB laser. Thereby a DFB fiber laser is provided which is relatively less sensitive to acoustic vibrations from the environment.

In a particular embodiment, said optical fiber is a silica-based optical fiber.

As an alternative to silica-based optical fibers, any other optical material fiber system can be used, such as polymers, aluminophosphate, fluorophosphate, fluorozirconate (ZBLAN), phosphate, boric acid Salts, tellurites, etc. (see e.g. Michel. JF Digonnet, "Rare-Earth-Doped Fiber Lasers and Amplifiers", ^2nd edition, 2001, Marcel Dekker, Inc., Chapter 2, pp. 17-112, which reference is at Known elsewhere as [Digonnet])

In a particular embodiment, said optical fiber comprises longitudinally extending microstructures.

In a particular embodiment, said optical fiber is a double-clad optical fiber. In one embodiment, the double-clad fiber comprises a core comprising an optically active dopant (eg rare earth ions such as Er and/or Yb) and (at least) an inner cladding and an outer cladding . This has the advantage that it allows the core of the optical fiber to be processed using cladding pumping techniques. In one embodiment of the invention, said optical fiber comprises longitudinally extending microstructures. In one embodiment of the invention, said optical fiber is a so-called air-clad fiber comprising an outer ring of air holes extending longitudinally (for example in the outer cladding region of said fiber), Pump light can be confined within the outer ring. This has the advantage of providing an attractive medium for fiber lasers. In yet another embodiment, said optical fiber is a double-clad optical fiber, wherein said inner cladding region is a multimode waveguide.

The position of the carrier surface within the package:

A beam package with straight-sided outer surfaces and a convexly curved fiber laser carrier surface is an excellent compromise solution, even in cases where the fiber laser cannot be precisely aligned along the neutral axis.

The term 'neutral axis' means in this application the axis in a structural part (typically a carrier for holding an optical fiber comprising a fiber Bragg grating) at which point when said structural part is deformed by e.g. pure bending The strain at the location of the axis is relatively small compared to the strain at other points in the structural part. The position of such a neutral axis can be determined, for example, by the Bernoulli-Euler simply supported beam theory (see e.g. the section "Position of the neutral axis" on pages 311-312 in [Timoshenko]) - assuming the groove width W _g corresponds to the given Compared with the width W of the above-mentioned carrier, see for example Fig. 12.b (for example W _g /W<0.2, for example <0.1).

In a particular embodiment, the curve defined by the contact channel of said supported portion of said optical fiber with said carrier surface is substantially part of a circle with radius R, said carrier having a longitudinal extension L, The Bragg grating has a grating strength κ, the carrier has a neutral axis N, wherein for κL greater than 1, in a transverse section at an intermediate position between the longitudinal ends of the carrier, the The distance h between said circle and said neutral axis is substantially equal to (4Rκ) ^-1 . This has the advantage that the frequency shift of the laser due to mechanical vibrations is very low.

A surprising result is that, in the mentioned approximation, the distance h is independent of the length L of the carrier.

The grating strength κ of a Bragg grating is a measure of the reflectivity per unit length (e.g. for index gratings the grating strength is determined by the modulation of the refractive index), see e.g. Andreas Othonos & Kyriacos Kalli (Artech House, 1999, ISBN: 0890063443), Chapter 5 "Fiber Bragg Gratings".

In a particular embodiment, κL is greater than 2, such as greater than 5, such as greater than 10.

In a particular embodiment, said carrier surface is substantially part of the surface of a circular cylinder, said cylinder having a radius R.

In a particular embodiment, the curve defined by the contact channel of said supported portion of said optical fiber with said carrier surface is substantially part of a circle of radius R, said curve when viewed in longitudinal section It is arranged symmetrically about the carrier center such that the apex of the circle is located midway between the longitudinal ends of the carrier (see eg Fig. 12.a).

The surprising result is that the optimal location of the contact channel of the supported portion of the optical fiber with the surface of the carrier is substantially below the neutral line of the carrier (as shown in Figures 11-13 when viewed as shown), and "the channel is substantially below" is understood in conjunction with the direction of the center of the circle of the curved contact channel, said path is generally located on the horizontal line representing the neutral axis of the carrier shown in Figure 12.a 87 below). In fact, the central part of the curve including the 'apex' at an intermediate position between the ends of the carrier is located slightly (eg 1-20 μm) above the neutral line. For the purpose of illustration of the individual geometrical parameters, this is not shown in Fig. 12.a, on the contrary, in said figure the contact path is located significantly above the line 87). A more (albeit incomplete) realistic interrelationship is shown in the cropped/zoomed-in view shown in Fig. 12.c.

In a particular embodiment, the distance h between the circle and the neutral axis is substantially equal to zero in a transverse section midway between said longitudinal ends of said carrier. In practice, the actual distance h of the physical embodiment can be determined by the tolerances set for the machine tools used to manufacture the carrier surface. In current machine tools, this tolerance is about 20 μm.

Other embodiments are defined in the dependent claims.

equipment:

The invention further provides a device comprising an article as described above and defined in the dependent claims.

The device may preferably constitute or be part of a laser detection and ranging (LIDAR) system or an interferometry system. LIDAR is an abbreviation for Laser Detection and Ranging and LIDAR systems are used, for example, to measure or measure distance, velocity, chemical composition, vibration and concentration, etc.). Interferometry systems can be used, for example, to measure mechanical vibrations, including acoustic vibrations, over long distances.

use:

The invention also provides the use of an article as described above and defined in the dependent claims. Preferably the article can be used in a LIDAR system or an interferometry system.

method:

Further provided is a method of producing an article, said method comprising the steps of:

(a) providing a length of optical fiber for a laser, said optical fiber comprising a fiber Bragg grating for wavelength selection of light guided in said optical fiber, said fiber Bragg grating being dispersed in said length of the FBG segment of the fiber optic,

(b) providing a carrier for supporting said optical fiber, said carrier comprising:

a carrier surface for supporting at least a supported portion of said optical fiber;

(b1) adapting the carrier surface so that the physical contact channel between the supported portion of the optical fiber and the carrier surface supporting the optical fiber is convex in the longitudinal direction of the optical fiber and is adapted to remain convex during use of the article; and

(c) mounting said supported portion of said optical fiber on said carrier surface of said FBG section comprising at least said length of said optical fiber such that said supported portion is above said optical fiber The FBG section of fiber is secured to the carrier surface on each side so as to provide longitudinal tension in the supported portion of the optical fiber during use of the article.

In a particular embodiment, the method further comprises adapting the encapsulation, in particular the portion of the encapsulation surrounding the carrier on which the supported portion of the optical fiber is mounted, to The step by which mechanical (eg acoustic) vibrations from the environment are minimized.

In a particular embodiment, step (b) further comprises the step (b2) of making said carrier comprise at least a first body and a second body made of different materials.

In a particular embodiment, step (b) further comprises the step (b3) of making said carrier comprise a material adapted for external modulation along the longitudinal dimension of said carrier.

In a particular embodiment, step (b) further comprises causing said different materials to include a first material suitable for thermal modulation along the longitudinal direction of said carrier and a second material suitable for external modulation along the longitudinal direction of said carrier. Step (b4) of the second material.

In a particular embodiment, step (b) further comprises the step (b5) of causing said carrier to comprise an outer boundary having at least one outer surface adapted to be fitted on a planar support.

In a particular embodiment, the method further comprises the steps of:

(d1) such that the curve defined by the contact channel of said supported portion of said optical fiber with said carrier surface is substantially part of a circle having a radius R, and such that said carrier has a longitudinal extension L,

(e1) giving said Bragg grating a grating strength κ,

(f1) determining the neutral axis N of said carrier,

(g1) such that for κL greater than 1, such as greater than 2, such as greater than 5, such as greater than 10, the circle and The distance h between said neutral axes is substantially equal to (4Rκ) ⁻¹ .

In a particular embodiment, step (g1) consists of such that in a transverse section midway between said longitudinal ends of said carrier, the distance h between said circle and said neutral axis is substantially Step (g2) equal to 0 replaces.

In a particular embodiment, the method comprises one or more, preferably all, of the following steps:

(d2) such that the curve defined by the contact channel of said supported portion of said optical fiber with said carrier surface is substantially part of a circle having a radius R, and such that said carrier has a longitudinal extension L,

(f2) determining the neutral axis N of said carrier,

(g2) such that in a transverse section at an intermediate position between the longitudinal ends of the carrier, the distance h between the circle and the neutral axis is substantially equal to 0, so that by the light guide The curve defined by the contact channel of the supported portion of the fiber with the surface of the carrier is substantially below the neutral axis in the direction of the center of the circle.

In a particular embodiment, step (a) further comprises the step (a1 ) of forming an optically active region in said supported portion of said optical fiber.

In a particular embodiment, step (a1) further comprises the step (a1.1) of completely or partially overlapping said optically active region with the spatial extension of said fiber Bragg grating.

In a particular embodiment, step (a1 ) further comprises the step (a1.2) of substantially not overlapping said optically active region with the spatial extension of said fiber Bragg grating.

In a particular embodiment, step (a) further comprises the step (a2) of causing said supported portion of said optical fiber to comprise at least two separate lengths of optical fiber, said at least two separate lengths The optical fibers are optically connected to each other, such as splicing.

In a particular embodiment, step (a2) further comprises the step (a2.1) of forming said fiber Bragg grating in a length of optical passive fiber.

The features of the method are the same as the advantages mentioned above in connection with the corresponding features of the article described in the section entitled "Article".

Other objects of the invention are achieved by the embodiments defined in the dependent claims and described in the detailed description of the invention.

It should be emphasized that when the term "comprises/comprising" is used in this specification, the term is intended to indicate the presence of specified features, integers, steps or components, but not to exclude one or more other specified features, integers, steps, components or its presence or membership in groups.

Description of drawings

Below, the present invention is described more fully in conjunction with preferred embodiment and accompanying drawing, wherein:

Figure 1 shows a prior art carrier with a fiber laser;

Fig. 2 shows a fiber laser fixed at each end of the package; Fig. 2.a and Fig. 2.b respectively show two extreme conditions of maximum deformation of the package during the vibration cycle;

Figures 3.a-3.1 show cross-sectional views of different articles comprising optical fibers assembled in packages, Figure 3.a being the prior art and Figures 3.b-3.1 being views according to the invention;

Figure 4 shows a semi-circular package, and Figures 4.a and 4.b show the two conditions of maximum deformation of the package during the vibration cycle (fundamental eigenmodes), where the undistorted figures are represented by unfilled figures package body;

Figure 5 shows a full circular package, in which the maximum deformation condition (basic eigenmode) of the package in the vibration cycle is shown, wherein the undeformed package is represented by an unfilled figure;

Fig. 6 shows a cylindrical package, Fig. 6.a is a perspective view, and Fig. 6.b and Fig. 6.c are sectional views along BB'B", respectively showing the optical fiber is placed on the surface of the carrier two examples;

Figure 7 shows the analytical formulas and approximate values of the section torsion factor K and the polar moment of inertia J for different beam sections;

Figure 8 shows a package according to the invention comprising a carrier substrate comprising a groove with a convex carrier surface, Figure 8.a shows a section along the longitudinal direction of the optical fiber, Figure 8.b A cross-section of the package end is shown and 8.c is a perspective view of the end;

Figure 9 shows an article according to the invention with a 'strongly' convex (semicircle solid, Figure 9.a) and a 'weakly' convex (Figure 9.b) carrier surface;

Figure 10 shows an article according to the invention, wherein the support surface is non-uniform, Figure 10.a shows the entire support and Figure 10.b shows an enlarged view of a small part of the support surface;

Figure 11 shows several embodiments of a package according to the invention comprising a carrier substrate with a through opening, Figure 11.a shows a cylindrical package with an outer surface of circular cross-section Perspective view, optical fiber is fitted on said outer surface, Fig. 11.b and Fig. 11.c show a sectional view (left) and a side view (right) of the carrier substrate, where the optical fiber is fitted in the through-opening , when the optical fiber is assembled on the carrier, the outer cross-sectional shapes of the carrier in the longitudinal direction perpendicular to the optical fiber are respectively circular (Fig. 11.b) and rectangular, such as square (Fig. 11.c);

Figure 12 shows a more detailed view of the carrier shown in Figure 8, Figure 12.a shows a side view along the longitudinal direction of the fiber, Figure 12.b is a front view of the end of the carrier and Figure 12.c is a view of the carrier Enlarged view of the end and center sections;

Figure 13 shows an example of an elongated package comprising one or more sections made of piezoelectric material according to the invention;

Fig. 14 shows an example of an elongated package according to the invention, said elongated package comprising a piezoelectric part inserted at a position close to the longitudinal end of the carrier, respectively, Fig. 14.a is a top view, Figure 14.b is a side view and Figure 14.c is an end view; and

Figure 15 shows several examples of a multi-body carrier comprising at least one body consisting of an optical fiber suitable for externally modulating the dimensions of the body in the direction of the supported portion of the optical fiber when the optical fiber is mounted on the carrier surface material.

The drawings are schematic and simplified for clarity, and only those details that are important for understanding the invention are shown, while other details are omitted.

Detailed ways

Figure 1 shows a prior art carrier 11 with a fiber laser 12, see eg [LVH-2002].

Different package designs have been developed to attenuate the effect of noise at the fiber laser frequency. Best results have been obtained by placing a fiber laser comprising a length of optical fiber on a neutral axis 16 in the carrier 11 of the package, where there is less deformation when the package is bent . Figure 1 shows an example of such a prior art package, where the fiber laser is placed in a trench 13 in the package. Here, the groove depth is designed such that the fiber laser is placed along the neutral axis of the package. The groove length 15 is greater than or equal to the length of the fiber laser. The neutral axis is determined by constructing the enclosure as a Bernoulli-Euler simply supported beam model and considering only pure bending. In this case, the neutral axis 16 exists in the package with zero deformation. According to the Bernoulli-Euler simply supported beam theory, this neutral axis is located at the position where the first area moment of the section is zero.

In the following, the maximum elongation of an optical fiber with a U-shaped groove base (see Fig. 1 and Fig. 2) is investigated.

When manufacturing the U-shaped channel base (or carrier) 11, certain tolerances are allowed to ensure proper assembly process. Coated optical fibers typically have a diameter of 250 μm. This diameter may vary from time to time, and may vary along the length of the fiber when the fiber is normally recoated (eg, after a Bragg grating has been written into the fiber). Typical variation is +/- 10µm.

Advantageously, the optical fiber 12 can be fitted in the groove 13 without friction. Accordingly, the grooves are typically made with a width 17 of 300-400 μm, with a tolerance of 25-75 μm on each side of the optical fiber to the sidewalls of the U-shaped groove (see FIG. 1 ). Not all cross-sections shown in FIG. 3 show this tolerance, but it is apparent that the embodiments have this tolerance.

The optical fiber 12 is secured at the ends (for example in each end of the groove 13) with a typical length between fixation points of 30 to 120 mm, usually about 60 mm.

In order to understand the maximum frequency shift due to the acceleration of the base 11, a simple geometry can be considered. It is assumed that the optical fiber 12 will remain at a fixed point in the center of the bottom of the groove (such as 23 shown in FIG. 2 ), and when the base is accelerated, the optical fiber contacts the U-shaped groove at an intermediate position between the fixed points. The (side) wall. In addition, the linear form of the optical fiber approximately functions as a triangle with a base length L (between fixed points) and a height h (the height is the height along the direction perpendicular to the optical fiber at an intermediate position between the fixed points of the optical fiber). (and groove) in the direction of the longitudinal direction of the maximum displacement from the center of the groove).

Where "h" is the distance the optical fiber can move from the center to the edge of the U-groove and L is the length between the fixed points, the length increase "d1" can be expressed as:

$\mathrm{<span\; class="notranslate">\; dl</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\sqrt{{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; L</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\sqrt{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; h</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}$

Since h/L<<1, the formula can be simplified as:

$\mathrm{<span\; class="notranslate">\; dl</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; h</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; L</span>}}$

In the case of L=60 mm, for a U-shaped groove with a tolerance of 25-75 μm, the length increase is 0.02 μm to 0.33 μm.

To further calculate the effect of this on frequency, the following formula can be used:

$\frac{\mathrm{<span\; class="notranslate">\; dl</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; df</span>}}{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; \&DoubleRightArrow;</span>\mathrm{<span\; class="notranslate">\; df</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; dl</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; h</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; f</span>}$

where _pe is the elasto-optic coefficient (about 0.21 for silica fibers, see eg WO-99/27400) and f is the optical frequency at λ = 1550 nm (about 193 THz).

The frequency shift associated with the length increase is then about 50-500 MHz (eg 52 MHz for h=25 μm and 474 MHz for h=75 μm).

A typical frequency shift of a free-running fiber laser is about 1 MHz/s and a typical fiber laser has a linewidth of 1 KHz. Comparing this frequency shift with the possible frequency shift associated with acceleration, it turns out that acceleration (eg from induced mechanical vibrations) can have a large impact on the spectral performance of a fiber laser.

The force required to displace an optical fiber at the center between the fixed points by a distance "h" in a direction perpendicular to the longitudinal direction of the fiber can be approximated as

F＝2*T*(h/L)

where T is the tension in the fiber in [N].

As an example, L = 60 mm, T = 0.22 N, and h = 25 μm results in a force F = 183 μN. Forces perpendicular to the axis of the fiber can be generated, for example, by acoustic or other mechanical vibrations or by directly accelerating the package.

To improve acceleration, the base can be processed without causing a frequency shift, at least two things can be done.

1) Some kind of material is introduced between the optical fiber and the wall of the U-shaped groove. This will prevent the fiber from moving during acceleration. If the density of the material is equal to that of the optical fiber, the prevention of movement can be substantially achieved. The materials are advantageously chosen so as not to induce stress in the fiber causing chirp effects in the fiber Bragg grating to degrade the performance of the laser.

2) Introducing a pretension between the optical fiber and the base, which can be achieved by fitting the optical fiber on a convex carrier surface. Given a predetermined insensitivity to acceleration, the pretension required at a given convex curvature and tension can be calculated.

An approximate expression for the maximum acceleration to ensure that the optical fiber does not detach from the carrier surface can be:

Acc<T/(ρL*r)

where r is the radius of curvature of the support surface. The table below shows an example where ρ _L = 9.8175·10 ^-5 kg/m (silica fiber) and T = 0.22N.

Radius r[m] 1 10 100 228 Acceleration Acc[m/s ² ] 2240 224 22.4 9.82 Corresponding sinusoidal vibration amplitude at 1000 Hz [μm] 56 5.6 0.56 0.25

This indicates that the 'breakaway' acceleration becomes relatively large for even larger radii of curvature. For example, for a radius of curvature of 1 m, an acceleration 200 times greater than the acceleration due to gravity (g ~ 10 m/s ² ) is required, which makes the laser relatively less sensitive to mechanical vibrations compared to prior art solutions . Further, if r<228m, the package can be placed anywhere in the gravitational field, e.g., to rotate the fiber downwards (i.e., in the direction of gravity) without breaking the fiber off the convex carrier surface (if if no other forces affect the package). Dynamic acceleration further limits the radius, where for example shock shocks can provide extreme acceleration, and therefore smaller radii are desirable (the actual radius of curvature is determined with the optical properties of the fiber laser in mind).

Figure 2 shows a fiber laser secured at each end of a longitudinally shaped package. Fig. 2.a and Fig. 2.b respectively show two extreme conditions of maximum deformation of the carrier 21 of the package during the vibration cycle. The optical fiber 24 is mounted on the carrier under tension, but is only secured at each end 23 of the optical fiber (for example with an adhesive). In an extreme bending mode as shown in FIG. 2. a, the optical fiber 24 follows the convex carrier surface 26. However in the extreme opposite to the bending mode (Fig. 2.b), the central part of the fiber may have poor contact with the carrier surface (break away from said surface) due to the pre-strain of the fiber. Figure 2.b shows this effect, where the fiber 24 has escaped from the concave surface 27. An unintended length change (length reduction) of an optical fiber comprising a fiber Bragg grating unintentionally changes the optical properties of the fiber (eg, the wavelength selection of the fiber Bragg grating).

However, besides bending, other deformation modes such as axial and torsional deformation also negatively affect acoustic sensitivity. Axial deflection is usually a problem only at high frequency noise. But when the bending effect is attenuated with a package in which the laser is mounted on the neutral axis, torsional deformation effects are observed for mid-range noise. To this end, this paper studies the problem of how to design the package so that the effects of bending and torsional deformation modes on the fiber laser are as small as possible.

The following strategies are advantageously utilized to reduce deformation of a fiber laser secured to a rigid, elongated package when the package is excited by noise or other mechanical vibrations:

• Fixing the laser in place on the package such that the laser elongates as little as possible when the package is excited in the problematic deformation mode.

- Increasing the natural frequency of the lowest deformation mode such that the total deformation of that mode is reduced for low frequency noise.

• Ensure good physical contact between fiber and package (avoid detachment).

The total deformation is advantageously reduced by increasing the natural frequency - even though it is possible to find an axis where the laser does not deform in a given mode, since the radius of the laser is greater than zero (ie the radially outer portion of the fiber will not be in the central axis or channel). Further, in some cases it may be difficult in practice to place the optical fiber precisely on a given central axis.

Conventional fiber laser packages are generally long compared to the cross-sectional area and are therefore considered 'beams' herein. have a large ratio of length to cross-sectional area (i.e., for example L>10*D or L>20*D, where L is the length of the fiber laser and D is the representative cross-sectional dimension of the optical fiber, such as its diameter, yet have a smaller The design of the ratio of L/D may have a similar effect, for example, the natural frequency of a long beam with L>5*D) can be approximated as:

$\left(1a\right){\mathrm{\&omega;}}_i^2={\mathrm{\&gamma;}}_i^4\frac{1}{{\mathrm{<figure-callout\; id="4"\; label="l"\; filenames="A20058002113100581.png"\; state="\{\{state\}\}">l</figure-callout>}}^4}\frac{\mathrm{E.}}{\mathrm{\&rho;}}\frac{1}{A}$ bending

$\left(1b\right){\mathrm{\&omega;}}_i^2={\mathrm{\&gamma;}}_i^2\frac{1}{l^2}\frac{G}{\mathrm{\&rho;}}\frac{K}{J}$ reverse

$\left(1c\right){\mathrm{\&omega;}}_i^2={\mathrm{\&gamma;}}_i^2\frac{1}{{\mathrm{<figure-callout\; id="2"\; label="l"\; filenames="A20058002113100631.png"\; state="\{\{state\}\}">l</figure-callout>}}^2}\frac{\mathrm{E.}}{\mathrm{\&rho;}}$ portrait

The relevant parameters can be divided into several groups: material parameters, density ρ, Young's modulus E and shear modulus G=E/(2/(1+V)), where v is Poisson's ratio. Geometric shape parameters, sectional area A, length 1, moment of inertia I, polar moment of inertia J and section torsion factor K. The constant γi depends on the assembly of the package. For free-free assembly (ie encapsulation in a soft sound-absorbing material, such as foam), the first set of these parameters is shown in the table below.

i γ _i bend γ _i reverse γ _i longitudinal 1 4.73004 π π 2 7.85320 2π 2π 3 10.9956 3π 3π 4 14.1372 4π 4π

For long beams, the natural frequencies of the bending modes are generally lower than the corresponding natural frequencies of the torsional and longitudinal modes, the actual relationship of the frequencies to each other depending on the geometry of the beam in question. From (1) it can be seen that the natural frequency increases if the package length l is shortened or if a material with a higher stiffness-to-mass ratio (E/ρ or G/ρ) is used. The natural frequencies of the bending and torsional modes also depend on the section design. A section with a higher moment of inertia to area ratio (I/A) increases the bending natural frequency, and similarly, a section with a higher ratio of torsional factor to polar moment of inertia (K/J) increases the torsional natural frequency.

The section torsion factor K is determined by the following formula:

M=GK(/l) _Ar4

where M is the moment required at both ends to twist a rod or beam of length l by an angle . GK is known as the torsional stiffness factor, which is the product of the material-dependent shear modulus G and the cross-sectional torsion factor K.

Analytical formulas and approximate values for K are known for certain types of cross-sections. Figure 7 shows some examples. But generally only analytical solutions for circular and thin-walled sections are known. The section torsion factor of a circular section is equal to the polar moment of inertia J of the section:

J＝∫r ² dA

In this case, the ratio K/J is 1 and has a maximum value.

But even for general cross-sections for which analytical expressions cannot be established, some suggestions for maximizing the ratio K/J can be given based on the simplified cross-sections shown in the above table:

• Maximize the K/J ratio and torsional natural frequency, if possible, with circular cross-sections.

· Open sections are not used, which results in a significant reduction in torsional stiffness compared to closed sections.

·Using double symmetrical sections, the shear center coincides with the bending neutral axis. This provides the fiber laser with minimal elongation in bend and twist modes when the fiber laser is positioned along this axis.

A circular cross section with a small hole in the center to accommodate the fiber laser is optimal. But packages with square cross-sections may be easier to manufacture and handle. A package with grooves designed to reduce the elongation of the fiber laser when the package is bent (see Fig. 3.a) should be modified to improve its torsional performance. By closing the grooves (see Fig. 3.b), a higher torsional stiffness and K/J ratio can be obtained. If the remaining hole is square and placed at the center of the section, it is bisymmetric and has coincident neutral and shear axes (also at the center). A comparison between a package with trenches (Fig. 3.a) and a closed package (Fig. 3.b) is disclosed in Example A below.

FIG. 3 shows an optical fiber 12, 32 comprising an optical fiber (for example forming an optical fiber A cross-sectional view of different articles 10, 30 of a part of a laser.

Figure 3.a shows a cross-section of the prior art package shown in Figure 1 with the optical fiber 12 fitted in a groove 13, eg on the central axis of the package (see 16 in Figure 1). Please note that the cross-section of Fig. 3.a is not prior art when used in combination with the embodiment shown in Figs. 4, 5, 8, 9 or an equivalent embodiment.

Figures 3.b - 3.1 show different embodiments of packages according to the invention. The centerline of the optical fiber preferably coincides with the neutral axis of the package.

Figure 3.b shows a double body package with a first U-shaped carrier body 31 and a second closing body 35 adapted to cooperate with the U-shaped body to be formed in the carrier for assembly with At least one optical fiber 32 of a fiber Bragg grating, such as a fiber laser, has a square through opening or cavity 36 . The two bodies together have a rectangular (possibly square) outer profile.

FIG. 3.c shows a dual body package as shown in FIG. 3.b, wherein the optical fiber 32 is surrounded by a filling material 37 . Further, the second closing body 35 consists of the same or another filling material. The filling material should preferably have a mass density which is comparable to (eg lies between) the mass density values of the optical fiber and the carrier material.

Figure 3.d shows a single body package with a through opening or cavity 36 of rectangular cross-section, wherein the optical fiber 32 is surrounded by a filling material 37. The package body has a rectangular (possibly square) outline.

FIG. 3.e shows a single body package with a through opening or cavity 36 of circular cross-section, wherein the optical fiber 32 is surrounded by a filling material 37 . The package body has a rectangular (possibly square) outline.

Fig. 3.f shows a double body package as shown in Fig. 3.c, wherein the contact surface 38 of the closing body 35 with the optical fiber 32 is adapted to the shape of the optical fiber (and wherein the optical fiber is surrounded by a filling material 37).

Figure 3.g shows a double body package comprising a first U-shaped carrier body 31 and a second T-shaped closure body 35 (comprising horizontal members 351 and side members 352), said second T-shaped closure body being adapted to Cooperates with the U-shaped body to form a square through opening or cavity 36 in the carrier for fitting the optical fiber 32 . The package body has a rectangular (possibly square) outline. The central 'leg' 352 of the 'T' is adapted to fit within the groove of the first U-shaped carrier body 31 to form the cavity 36, thereby enabling ease of handling and ease of self-aligned packaging. The two bodies 31 , 35 constituting the carrier of the package are fixed to each other by means of an adhesive 352 . In the part of the carrier extending in the longitudinal direction of the optical fiber 32, the adhesive may be added over the entire contact surface between the two bodies or one or more discrete strips of adhesive applied along the length of the carrier. The adhesive stop 353 is shown in the form of a small groove or ditch. The purpose of the adhesive stop is to prevent adhesive from traveling to the cavity 36 containing the optical fiber 32 .

Figure 3.h shows a double body package comprising a first U-shaped carrier body 31 and a second rectangular closing body 35 adapted to cooperate with the U-shaped body to form in the carrier for A square through-opening or cavity 36 in which the optical fiber 32 is fitted. The inner faces of the 'legs' of the U include steps that narrow the portion of the groove that holds the optical fiber 32 . The package body has a rectangular (possibly square) outline. The two bodies 31 , 35 constituting the carrier of the package are joined by an adhesive 35 . The adhesive stop 353 is shown in the form of a small groove or ditch.

Figure 3.i shows a dual body package comprising a first U-shaped carrier body 31 and a second trapezoidal closure body 35, the side 'legs' of the 'U' having inwardly sloping faces, the second trapezoidal closure body 35 The body is adapted to cooperate with the U-shaped body to form a square through opening or cavity 36 in the carrier for fitting the optical fiber 32, thereby allowing easy handling and easy self-aligning packaging. The optical fiber is surrounded by a filling material 37 . The package body has a rectangular (possibly square) outline.

Figure 3.j shows a single body package with a circular profile, with a circular through-opening or cavity 36 in the carrier to fit the optical fiber 32, thereby providing the ideal cross-section to provide the package with high natural frequency. The optical fiber is surrounded by a filling material 37 .

Figure 3.k shows a package as in Figure 3.j, except that the circular cylindrical carrier 31 is formed from two bodies (two halves) 31,35.

Figure 3.I shows the package as in Figure 3.j, except that the through-opening or cavity 36 in the carrier for fitting the optical fiber and the duct fiber itself 32 has an oval cross-section.

Figure 4 shows a semi-circular package, and Figure 4.a and Figure 4.b show the conditions of the two maximum deformations (fundamental eigenmodes) of the package during the vibration cycle, where the unfilled figures represent the unfilled The package body 41 is deformed.

Figure 4 shows the package formed into a semi-circular shape in its undeformed state and in its deformed state. Figures 4.a and 4.b respectively show the eigenmodes 42 corresponding to the fundamental resonance frequency. As shown, even if the top surface is deformed by vibration corresponding to the fundamental resonance frequency, the top surface remains convex. Lifting off the surface is avoided by securing the lasers to the surface at each end of the package.

By providing grooves in the semicircular package it is possible to fix the laser at the neutral axis (in this case forming a semicircle). If the cross-sectional area is small compared to the radius of the semi-circular package, the groove depth of the cross-section can be calculated in the same way as for the straight-sided package. The cross-section of the package body in the direction perpendicular to the longitudinal direction of the optical fiber may take any suitable shape, including the shapes shown in Fig. 3.a-Fig. 3.I.

Instead of using a package shaped as a semicircle, the fundamental resonant frequency can be increased by closing the circle. Figure 5 shows a full circle package. The fundamental resonance frequency can thus be increased by 45% compared to a semicircular package.

FIG. 5 shows a full circular package, and FIG. 5.a and FIG. 5.b show the condition of the maximum deformation of the package during the vibration cycle, the fundamental eigenmode 52 . The undeformed package body 51 is represented by an unfilled figure.

The cross-section of the package body in the direction perpendicular to the longitudinal direction of the optical fiber may take any suitable shape, including the shapes shown in Fig. 3.a-Fig. 3.I.

Fig. 6 shows a cylindrical package, Fig. 6.a is a perspective view, and Fig. 6.b and Fig. 6.c are cross-sectional views along BB'B", respectively showing that an optical fiber 63 is placed on a carrier surface 62 Two embodiments on and placed in the groove 66. The optical fiber 63 includes a fiber Bragg grating 64 between the fixing points 63 at which the optical fiber is fixed on the carrier surface 62.

A package shaped as a cylinder has an extremely high fundamental resonance frequency. A preferred typical package may be an aluminum cylinder with a diameter of 44.6mm and a height of 20mm.

The intrinsic resonant frequency is 35kHz, well above the audible region (0Hz to 20Hz).

Figure 8 shows an article 80 according to the invention comprising an elongated (beam-shaped) package having (at least one, here all) planar outer surfaces (suitable for mounting on a planar support), the The package has a length L, a width W and a height H of the carrier 81, which includes a groove 83 with a convex carrier surface 86, Fig. 8.a shows a side view along the longitudinal direction of the optical fiber, Fig. 8.b is a front view of the package and Fig. 8.c is an end perspective view. The convex carrier surface 86 is suitable for mounting optical fibers (such as fiber lasers) attached at each end under longitudinal tension.

The cross-section of the package body in the longitudinal direction perpendicular to the optical fiber (that is, the cross-section shown in Figure 8.b) can take on any suitable shape, including those shown in Figures 3.a-Figure 3.I (including omitting embodiment of the second closed body 35 of the dual body package), while still retaining the convex 'longitudinal' form of the carrier surface.

Figure 9 shows an article 90 according to the invention having a carrier 91 with a 'strong' convex (semicircle solid, figure 9.a) and a 'weak' convex (fig 9.b) carrier surface, wherein the optical fiber 92 is attached to the carrier surface at points 93 on each side of at least one fiber Bragg grating in the optical fiber.

Both embodiments as shown have a generally planar carrier surface 99 opposite a carrier surface adapted to support an optical fiber. This has the advantage that it allows easy placement or assembly of the package in system environments including planar objects (such as most conventional electro-optic system components).

The optical fiber may or may not be located in the trench. With the optical fiber 92 in the groove, the convex shape of the carrier surface as shown is the shape of the carrier surface at the bottom of the groove where there is physical contact between the carrier and the optical fiber.

Preferred embodiments of the present invention are further described by the following examples.

Example A: "Double body package with cavity-enclosed body. Package with U-groove Body vs. Package with Enclosed Trench"

A comparison is made between a package with a central trench and a package with a central (through) hole (see eg Figure 3.a and Figure 3.b). Both packages had external dimensions of 5 mm x 5 mm x 70 mm and were made of aluminum (E=70 GPa, v=0.34, p=2700). The grooves have a depth of 2.65 mm and a width of 0.3 mm. The center hole is a square of 0.3mm x 0.3mm. The section constants of the two packages are shown in the table below.

I _xx I _yy J K K/J groove 50.5mm ⁴ 52.1mm ⁴ 103mm ⁴ 43mm ⁴ 0.418 hole 52.1mm ⁴ 52.1mm ⁴ 104mm ⁴ 88mm ⁴ 0.843

Sectional constants were calculated using the finite element program ANSYS, a commercially available software based on the finite element method, available from ANSYS, Inc., Canonsburg, PA 15317, U.S.A. It is possible to calculate the moments of inertia analytically, but usually only the section torsion factor K can be calculated numerically. Use (1a)-(1c) to calculate the first natural frequency (ω1).

bending reverse portrait groove 5.34kHz 14.4kHz 36.4kHz hole 5.43kHz 20.4kHz 36.4kHz round - 22.2kHz 36.4kHz

The lowest bending and torsional natural frequencies have been increased by closing the trench. Due to the double symmetry of closed sections, the neutral axis and the shear center coincide in circular holes (see eg [Timoshenko] p. 421). This reduces the amount of elongation of the fiber laser when the laser is placed on these axes and bent or twisted. However, the amount of elongation of any axis in the package torsionally deforms is already small, but by placing the laser at the center of the shear the laser remains on the line rather than deforming into a helical shape. Even if the amount of elongation produced when the laser is placed at the shear center and on the neutral axis is negligible, twisting of the fiber laser cannot be avoided when the package is torsionally deformed. The twisting of the fiber generates shear strain in the fiber, which will indirectly affect the optical medium through the photoelastic effect that causes the main axis of the anisotropic fiber medium to rotate. But this effect can be mitigated by shifting the torsional natural frequency away from (in this case upward in this case) the introduced noise frequency.

Example B: "Package with an irregular but generally convex carrier surface"

This example relates to an embodiment of the invention wherein the carrier surface is macroscopically convex but includes peaks and valleys or ridges and valleys on the carrier surface so that the surface-adaptive portion of the optical fiber is subjected to peaks or ridges Irregular in the sense that a portion is supported (eg, physically rests on the peak or ridge) but does not make physical contact with a valley or valley on the surface.

Figure 10 shows such an article 100 in which the surface 106 of the carrier 101 is non-uniform.

Figure 10.a shows the entire carrier with the optical fiber 102 mounted under tension on the convex surface 106 by welding or adhesive spots 103. The bottom surface 109 (opposite the carrier surface 106 for supporting the optical fiber 102 ) is convex and has substantially the same shape as the carrier surface 106 .

FIG. 10 . b shows an enlarged view of a small portion of the carrier surface 106 . Inhomogeneous features of the carrier surface 106 emerge, represented by peaks 107 and valleys 108 . The figure shows the maximum distance L 110 between two adjacent peaks along the longitudinal direction of the surface-adapted portion of the optical fiber 102. Appropriate L values are calculated below as illustrative examples.

The eigenfrequency of a vibrating string is given by the following expression (boundary condition: fixed-fixed, similar to a guitar string):

${\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; L</span>}}\sqrt{\frac{\mathrm{<span\; class="notranslate">\; T</span>}}{{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}}}$

where f _n is the eigenfrequency [Hz], n=1, 2, 3, ..., L is the length of the string [m], T is the tension in the string in N, and ρ _L is the linearity of the string Mass density (mass per unit length) [kg/m] (see Chapter 2: "Transverse motion: The Vibrating String", p. 52, Kinsler, LE; Frey, AR; Coppens AB; Sanders, JV: "Fundamentals of Acoustics", 4th Edition, 2000, John Wiley & Sons, Inc).

Typical parameters for optical fibers with silica glass core and polyvinyl chloride (PVC) coating are:

ρL＝2600kg/m ^3* π/4*(125μm) ² +1800kg/m ^3* π/4*((250μm) ² -(125μm) ² )＝9.8175·10 ^-5 kg/m

T[N] L[m] n f _n [Hz] Ex1 1 1· ^10-2 1 5046 Ex2 1 0.25·10 ^-3 1 20185 Ex3 0.22 1· ^10-2 1 2367 Ex4 0.22 1.1· ^10-3 1 21517

Examples 3 and 4: The tension in the string T=0.22N represents a minimum pre-strain of the optical fiber such that the wavelength change is 0.3nm relative to λ=1550nm.

Conclusion (of Example B): The distance between peaks or ridges along the direction of the surface adaptation portion of the optical fiber should preferably be less than 1mm (under the above conditions) in order to shift the natural frequency to values 20-20kHz above the acoustic frequency range.

Fig. 11 shows several embodiments of a package according to the invention comprising a carrier substrate with a through-opening.

Figure 11.a shows a perspective view of a package 110 with a cylindrical carrier 111 with an outer surface 116 of circular cross-section, on which an optical fiber 112 comprising a fiber Bragg grating 114 is mounted On the whole, it is basically the same as that shown in FIG. 6 . The difference from the embodiment shown in Fig. 6 is that the carrier shown in Fig. 11.a comprises a through-opening 1112 along the axis 1111 of the cylindrical carrier. The purpose of the through openings of the embodiment shown in Fig. 11.a is to save material compared to a solid carrier. Further, the hollow portion of the package may contain other components, thereby providing a compact package when the package is mounted on a planar substrate (such as a printed circuit board or another substrate) using one of its planar outer surfaces 119. system.

Fig. 11.b and Fig. 11.c show a cross-sectional view 1201, 1301 (left) and a side view (right) of a package 120, 130 with a carrier substrate 121, 131, wherein an optical fiber 122, 132 is assembled in a through In the openings 1212, 1312, when the optical fiber is assembled on the carrier, the outer cross-sectional shapes of the carrier in the longitudinal direction 1211, 1311 perpendicular to the optical fiber are respectively circular (Fig. 11.b) and rectangular such as square (Fig. 11.b). .c). The optical fibers 122, 132 may be any type of optical fiber suitable for use as an optical fiber for a fiber laser, here a double clad fiber is shown, specifically shown comprising a central core region 1223, a microstructured inner cladding 1222 and A microstructured fiber comprising an 'air cladding' outer cladding 1221 with a ring of air holes enclosing the space. In the fiber 122 shown in Fig. 11.b, a single centrally located (in the longitudinal sense) Fiber Bragg Grating 24 is shown, such as used in DFB lasers. In one embodiment, a fiber Bragg grating 124 is located in the optically active region of the DFB laser. In the fiber 132 shown in Fig. 11.c, two spaced Fiber Bragg Gratings 134 are shown, such as those used in DBR lasers. The purpose of arranging the optical fiber in the through-opening is to provide a package with increased stiffness and a relatively high natural frequency in the lowest deformation mode. In one embodiment, a DBR laser includes an assembly in which two fiber Bragg gratings 134 are each formed in separate passive optical fibers of a length—spatially separated by an optically active region—with the passive optical fiber comprising A length of optical fiber splices the optically active region of the DBR laser. A similar DFB laser or DBR laser (one fiber or packaged solution) can be implemented by any other embodiment of the invention. The cross-sectional dimensions in the longitudinal direction 1211, 1311 perpendicular to the optical fiber are exaggerated compared to those in the longitudinal direction. The convexly shaped carrier surface for supporting the optical fiber is not shown in the figure. The package 130 and carrier 131 of the embodiment shown in FIG. 11. c are particularly suitable for mounting on planar substrates due to their planar outer surface 139 . A further difference between the embodiments shown in Fig. 11.b and Fig. 11.c is that the optical fiber 132 shown in Fig. 11.c including the fiber Bragg grating 134 is directly supported by the open carrier surface (similar to Fig. 11. The filler material shown in b may surround the optical fiber 122 and may fill the opening space in the opening around the fiber or spacer to keep the fiber substantially centered in the opening).

Figure 12 is the same as Figure 8 except for certain structural parameters shown in Figure 12 . Figure 12 shows the radius of curvature R of the convex carrier surface 86 (here a circular cylindrical surface). The figure further shows the maximum distance h between the neutral axis 87 of the package and the carrier surface 86 . FIG. 12 . b further shows the height H _g and width W _g of the section of the groove 83 in a direction perpendicular to the longitudinal axis of the carrier 81 . Carrier 81 has at least one substantially planar surface suitable for mounting on a substantially planar support such as a substrate on which other optical, electronic and/or opto-electronic components may be mounted and which may be connected to form a module. The outer surface of 89. In the longitudinal section shown in Fig. 12.a, it is also shown that for a symmetrically arranged circle of radius R (see 'L' and 'L/2' in Fig. 12.c), the circular support surface The maximum height h _c beyond its level at the longitudinal ends (cf. 76 , 77 in FIG. 13 ). Example 4 below gives the formula for calculating _hc . Figure 12.c shows an enlarged view of the end and central parts of the carrier. The ratio of h to h _c is usually in the range of 0.01 and 0.05.

The position of the neutral axis in a given package is discussed in [Timoshenko] pp. 311-12 if the package is considered to be a beam.

In Examples 1 and 2 below, approximate expressions for h are given to minimize the sensitivity of the article 80 including the carrier 81 to mechanical vibrations. These expressions relate to the embodiment discussed in connection with Fig. 8 and Fig. 9b having the cross-sections discussed in connection with Figs. 3.a to 3.i and the embodiment discussed in connection with Figs. 11-14 and Fig. 15.b.

If R is large (i.e., for example, R > 10H, where H is the carrier height, see Fig. 12.a) and the width W _g of the trench is small compared to the width W and height H of the carrier section (Fig. 12.b) ( That is, for example W _g /W<0.30), it can be assumed that a small change in h will not change the neutral axis. Assuming that the package deforms in pure bending mode, it is known from Charpy beam theory that the axial strain (axial means along the central axis of the optical fiber located in the package) increases linearly with the distance from the neutral axis (see e.g. JMGere and SPTimoshenko, "Mechanics of Materials", Fourth SI Edition, Stanley Thhomes (Publishers) Ltd. 1999).

Example 1: Ad hoc approximation of DFB fiber laser (Ad hoc approximation)

Integrating the axial strain over the length of the optical fiber gives:

$<span\; class="notranslate">\; \&Integral;</span>\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; dl</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; \&Integral;</span>\mathrm{<span\; class="notranslate">\; Cydl</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; C</span>}\underset{\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}}{<span\; class="notranslate">\; \&Integral;</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; d\&alpha;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; )</span>$

where y is the coordinate perpendicular to the neutral axis (ie perpendicular to the longitudinal direction of the carrier), α _L =arcsin(L/2R). Assuming this expression is zero, the distance h from the neutral axis (87 shown in Figure 12.a) is calculated as:

$\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; arcsin</span>}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; L</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \&ap;</span>\frac{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="L"\; filenames="A20058002113100631.png"\; state="\{\{state\}\}">L</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; twenty\; four</span>}\mathrm{<span\; class="notranslate">\; R</span>}}$

This expression weighs the importance of axial strain equally along the length of the DFB fiber laser. The table below shows the calculated results of h for different values of carrier length L and radius R for a convex carrier surface.

Table 1: Typical calculation results for h obtained for typical L and R values

L[mm] R[m] h[μm] 7550 1.51.5 15669.4 50 1.0 104

According to these calculations, when L decreases, h decreases rapidly.

Example 2: A more accurate approximation of h for a DFB fiber laser

A more accurate approximation of the optimal h value can be obtained by requiring that the shift in laser generation frequency be zero when the package is purely bent. The frequency shift of a DFB fiber laser affected by a distributed strain field, which can be obtained from [S.Foster, "SpatialMode Structure of the Distributed Feedback Fiber Laser", IEEE J.Quant.Elect., 40, July 2004] is:

Δω(t)=L _c ω∫ε(z,t)e ^-2kz dz

where Δω is the frequency shift, _Lc is the cavity strength, ω is the lasing frequency, ε is the axial strain, k is the grating strength and z is the direction along the fiber length. The pure bending axial strain along the circular segment is:

$\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; z</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>\sqrt{{\mathrm{<span\; class="notranslate">\; R</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; z</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; )</span>$

The frequency shift can be found using the integral method by integrating over the length of the fiber laser, and the optimal value of h can be found by setting the resulting frequency shift to zero and solving the resulting equation for h, thus obtaining the following:

$\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&kappa;</span>}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&kappa;L</span>}}}\underset{\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 2</span>}}{<span\; class="notranslate">\; \&Integral;</span>}}{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&kappa;L</span>}}\sqrt{{\mathrm{<span\; class="notranslate">\; R</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="z"\; filenames="A20058002113100631.png"\; state="\{\{state\}\}">z</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}\mathrm{<span\; class="notranslate">\; dz</span>}$

That is, under the condition of 1<<κL

$\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; \&ap;</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 4</span>}\mathrm{<span\; class="notranslate">\; R</span>}{\mathrm{<span\; class="notranslate">\; \&kappa;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}$

The calculations of h obtained for different values of L, R and κ are shown in Table 1 below, the column headed 'h[μm]' indicates the more precise value from the exact formula given above, and The column headed by '≈h[μm]' represents the value calculated according to the approximate formula given above under the approximate condition of 1<<κL.

Table 2: Example calculations for h obtained for typical L, R, and k values

L[mm] R[m] K[m ^-1 ] h[μm] (≈h[μm]) 756050757575 1.51.51.51.01.51.0 150150150150100100 7.407.367.2611.1016.3424.51 (7.41)(7.41)(7.41)(11.11)(16.67)(25.00)

It can be seen from Table 2 that h is relatively small (compared to the physical height dimension of the carrier in mm order) and relatively independent of the length L of the carrier. It can further be seen that the approximate formula provides results (data in parentheses in the rightmost column) that are quite close to those of the exact formula (second to last column). For approximate calculations, κL > 7.5.

Example 3: Package with Improved Tuning Options

Figure 13 shows an elongated package comprising one or more segments of piezoelectric material in accordance with the present invention.

The material of the carrier is usually chosen with regard to the base material of the optical fiber being supported by the carrier (and possibly by introducing some degree of pre-straining of the optical fiber). This makes it possible to take into account the correlation between possible temperature differences and the corresponding thermal expansion coefficients, so that it is ensured that no shedding occurs within the predetermined temperature range during operation.

In one embodiment, the majority of the volume of the package that determines the thermal expansion of the carrier surface comprises aluminum. This has the advantage of providing a thermally conductive carrier, a relatively inexpensive material and an attractive material for machining. If only fast modulation is of interest, most carriers use materials with a low coefficient of thermal expansion such as Invar(R) or materials with a coefficient of thermal expansion similar to that of optical fibers. In other embodiments, most of the carriers can use ceramic or piezoelectric materials.

The four different carriers 81 shown in FIGS. 13.a to 13.d comprise at least two different materials 71 , 72 . A part of the carrier is made of a material 1 with a relatively high thermal expansion coefficient, so that the carrier or a part of the carrier can be heated or cooled to achieve the purpose of tuning in a relatively large wavelength range, but the tuning is relatively slow in nature. The other part of the carrier is made of a material 2 for which the physical dimensions can be modulated at relatively high frequencies, whereby relatively fast wavelength tuning can be achieved, however, the tuning is usually at relatively small within the wavelength range. By having the carrier partly made of material 1 and partly made of material 2, a combined property of both properties, ie large range thermal tuning and fast modulation tuning, can be provided.

Material 1 may be any suitable material with a relatively high coefficient of thermal expansion. Other relevant parameters of the carrier are thermal conductivity (preferably relatively high), machinability, etc. The coefficient of thermal expansion of material 1 is related to the coefficient of thermal expansion of material 2. A relatively high coefficient of thermal expansion may thus be a coefficient of thermal expansion that is greater than the coefficient of thermal expansion of the material 2 . The relatively high coefficient of thermal expansion may thus be greater than α _T-2 , eg greater than 1.5*α _T-2 , eg greater than 2*α _T-2 , eg greater than 5*α _T-2 , eg greater than 10*α _T-2 . For piezoelectric ceramic materials, the coefficient of thermal expansion may be in the range of 1*10 ⁻⁶ °C ⁻¹ to 5*10 −6 °C ₋₁ . The adopted relatively high coefficient of thermal expansion may be greater than 10*10 ^-6 °C ^-1 , eg greater than 20*10 ^-6 °C ^-1 , eg greater than 25*10 ^-6 °C ^-1 . The material 1 may be selected from the group of materials comprising Al, Cu and their alloys and eg ceramics and combinations thereof. In general, the carrier can be designed with a material having a positive, zero or negative coefficient of thermal expansion (see eg WO=99/27400) or an appropriate combination thereof.

Material 2 may be any material that can modulate physical dimensions over a range of modulation frequencies, such as piezoelectric, electrostrictive or magnetostrictive materials. The modulation frequency appears to be related to the possible thermal cycling frequency that Material 1 has. The modulation frequency is advantageously less than 10 MHz, preferably in the range 0.1 Hz to 100 kHz, for example in the range 10 Hz to 40 kHz, for example in the range 20 Hz to 20 kHz. The material 2 may be selected from the group of materials comprising piezoelectric materials, such as piezoelectric ceramic materials, such as polycrystalline ferroelectric ceramic materials, such as barium titanate and lead zirconate titanate (Pb) (PZT), and combinations thereof.

Material 1 is preferably aluminum and is shown as a white area in FIG. 13 (shown by reference number 72 ), while material 2 is preferably a piezoelectric ceramic material and is shown as a gray area in FIG. 13 . All four packages have a convex laser carrier surface to reduce noise from mechanical vibrations.

Figures 13.a to 13.d show longitudinal cross-sections (left) of four different carriers 81 and a transverse direction perpendicular to the longitudinal section taken along line 75 at an intermediate position between the ends 76, 77 of said carriers. Section (right) ('Central section'). All four embodiments have at least one generally planar surface 89 for ease of assembly on a planar carrier. However, this need not be the case. Alternatively, the carrier may have a curved outer surface, see eg FIGS. 4 , 5 , 6 , 9 , 10 . In all four embodiments, the carrier is symmetrical about the centerline 75 . While this is preferred, it need not be the case.

All four embodiments shown in FIG. 13 show articles according to the invention comprising an elongated (beam-shaped) carrier having (at least one, here all) planar outer surfaces (suitable for fitting on a planar carrier above), the length of the carrier 81 is L, the width is W and the height is H, and the carrier includes a groove 83 with a convex carrier surface 86 suitable for mounting an optical fiber (such as a fiber laser), The optical fiber is attached under longitudinal tension at each end 93 (as shown in Figure 13.d). While the carrier surface is preferably curved, this need not be the case. Alternatively, the carrier surface may be planar, see eg FIG. 1 . Alternatively, one or more of the outer surfaces of the carrier may be curved, see eg the embodiments shown in Figures 4.a and 4.b. In these embodiments, one ('side') surface may advantageously be adapted to fit on a planar support.

The cross-section of the package body in the longitudinal direction perpendicular to the optical fiber (that is, the right-hand side cross-section shown in Figure 13.a-Figure 13.d) can take on any suitable shape, including Figure 3.a-Figure 3.i The shape shown (including the embodiment in which the second closure body 35 of the double body package is omitted), while - optionally - still maintaining the convex 'longitudinal' shape of the carrier surface. The carrier may have any suitable cross-sectional shape in a direction perpendicular to the longitudinal direction of the supported portion of the optical fiber when the optical fiber is mounted on the carrier, although preferably comprising an outer surface adapted to fit on a planar support, Including those shapes shown in Fig. 3.j-Fig. 3.i.

Figure 13.a shows a carrier in which a section 71 of a carrier 81 is made of piezoelectric material, said section having substantially the same cross-section as the rest of the carrier, ie substantially continuing the adjacent aluminum carrier Section 72 of section. The dimension of the piezoelectric material section in the longitudinal direction of the carrier (represented by the left section shown in Fig. 13) is eg 25%, eg 20%, eg 10% less than the length of the total carrier. In one embodiment, the length L of the carrier is 75 mm, and the length of the piezoelectric section is preferably in the range of 1 mm to 10 mm, such as 2 mm to 5 mm, such as about 3 mm. In Fig. 13.a, the section of piezoelectric material is located away from the center portion of the carrier and near one end of the carrier. The modulation body is preferably located close to the center of the Bragg grating to achieve relatively high modulation. However, where it is difficult to control the mechanical tolerances on the piezoelectric material, it may be advantageous to place it at a location away from the (sensitive) center of the grating. The solution shown in Fig. 13.a provides good temperature tuning because the central part of the carrier is made of a material with a higher coefficient of thermal expansion (e.g. 45pm/K for a 1550nm laser housed in an A1 carrier ), the central sensitive section of the Bragg grating is located at the central part.

The only difference between Fig. 13.a and Fig. 13.b is that the embodiment shown in Fig. 13.b comprises two segments 71 made of piezoelectric material. The segments can preferably be arranged symmetrically with respect to the carrier center 75 and have the same longitudinal dimensions. The advantage of this solution is that it provides good temperature tuning and symmetrical loading. The term 'symmetric loading' means herein that it provides a symmetrical strain field in the optical fibre. Alternatively, the two sections can be arranged symmetrically and/or have different longitudinal dimensions.

In the embodiment shown in Figures 13.a and 13.b, the trench 83 in which the optical waveguide is seated is shown opening upwards. Typically the body is applied on top of the trench thereby forming a cavity (or through-opening) of the waveguide (see 73 shown in Figures 13.c and 13.d), eg in Figures 3.b, 3.c, Figure 3.f shows.

In Fig. 13.c, a centrally located longitudinally extending section of piezoelectric material 71 is shaped as a cover (eg plate) enclosing a slot or groove 83 in which the optical fiber is supported, thereby forming a tube surrounding the optical fiber Shape volume 73. The solution shown in Figure 13.c provides symmetrical loading.

In Fig. 13.d, a centrally located longitudinally extending section of piezoelectric material 71 is shaped as a U-shaped body (eg a plate) closing a slot or groove 83, thereby forming a tubular volume 73 in which an optical fiber is supported . The aluminum part 72 of the carrier 81 can be made in one piece, wherein the part consisting of the U-shaped section of piezoelectric material is removed by means of a numerically controlled machine. The solution shown in Fig. 13.d provides symmetrical loading. The fixing point 93 of the optical fiber is shown close to the longitudinal ends 76, 77 of the carrier.

In the embodiment shown in Figure 13, two different materials are used for certain sections of the carrier. Alternatively, more than two materials may be used.

The different bodies of the carrier may be joined by any suitable method of a variety of known joining methods, such as adhesives/adhesives.

Example 4: Physical dimensions of a typical package:

Table 3 gives an example of preferred dimensions of a carrier suitable for a package thermally tuned to wavelength according to the invention:

Table 3: Dimensions of typical carriers according to the invention

h Carrier height 3.0+0.0/-0.1mm L Carrier length 75.0+0.0/-0.1mm W Carrier width 3.0+0.0/-0.1mm H _g groove height 1.00+/-0.05mm _w groove width 0.34+0.05/-0.0mm h _c The height of the surface of the curved carrier 0.4688mm (calculated value) R The radius of the support surface defined as a circle 1500mm h The distance between the apex of the carrier surface and the neutral axis 7.40μm (see Table 2)

The parameters of the packages given in Table 3 should be understood in conjunction with FIG. 12 . The package carrier is made of Al, and the trenches in which the optical fibers are disposed are formed using an arc ablation process. The optical fiber is fitted in the groove and fixed at a point close to the longitudinal end of the carrier (see eg 93 in Figure 3d).

Calculate h _c from the following formula:

${\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\sqrt{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; L</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; )</span>$

Example 5: Tuning of a carrier with piezoelectric plates:

Figure 14 shows an embodiment of the invention in the form of a piezoelectric carrier 81 provided with piezoelectric plates 71 of the type schematically shown in Figure 13.a. This embodiment is suitable for (relatively low) thermal modulation and (relatively fast) electrical modulation of the carrier.

In a preferred embodiment, the dimensions of the carrier are the same as those shown in Example 4 above (see Table 3).

The dimensions of the piezoelectric plates are shown in Table 4 below:

Table 4: Dimensions of piezoelectric plates in a typical carrier according to the invention

H _ptz Piezo Plate Height 5mm lm _w The length of the piezoelectric plate 3mm W _ptz Piezo Plate Width 5mm Hg _{, ptz} Groove Height of the Piezo Plate 3.3mm Wg _{, ptz} Groove Width of the Piezo Plate 0.8mm

The fiber length L between fixed points on the carrier (see e.g. point 93 shown in Figure 13 which coincides with the adhesive reservoir 58 shown in Figure 14) _is 68 mm (compared to the physical length of the carrier of 75 mm mesh) .

The (here) silica-based optical fiber is secured to the carrier in the groove 83 under axial tension at the adhesive reservoir 58 near the longitudinal end of the carrier (eg, 1-5 mm from the end) on surface 86. Strain relief 53 is provided at each end of the carrier to allow easy handling of the optical fiber and carrier.

The tuning range Δλ of the wavelength λ can be expressed as:

Δλ(nm)=0.78*λ(nm)*dx(μm)/L _f (μm)

where 0.78 is the elasto-optic coefficient dn/dε (of an optical fiber, here a silica-based optical fiber) expressing the variation of its refractive index n with strain ε in the longitudinal direction (see e.g. WO-99 /27400), dx is the longitudinal dimension change of the optical fiber, and _Lf is the length between the fixed points of the optical fiber on the carrier surface.

The change dx of the longitudinal dimension of the piezoelectric plate can be expressed as:

dx(μm)＝d ₃₃ (m/V)*E(V/m)*L _pzt (μm)

where d ₃₃ is the piezoelectric gauge factor of the piezoelectric material (and carrier) along the longitudinal direction, E is the applied electric field strength (in the same direction), and L _ptz is the dimension of the piezoelectric plate along the longitudinal direction of the carrier.

For _Lf = 68mmm, _Lptz = 3mm, _d33 = 425pC/N (Pz27 material), _Emax = 3MV/m and λ = 1550nm, the following corresponding Δx and Δλ values can be obtained:

For Pz27, Δx _max = 3.82 μm and Δλ _max = 68 pm

Pz27 is a piezoelectric ceramic material from Ferroperm Piezoceramics A/S (Kvistgaard, DK3490-Denmark, http://www.ferroperm-piezo.com).

Available for example from Noliac (Kvistgaard DK-3490, Denmark, http://www.noliac.com/ ) or Piezo systems, Inc. (Cambridge, Mass. 02139, USA, http://www.piezo.com/) Piezoelectric and/or piezoelectric stretchable materials.

Example 6: Multiple multi-body carriers including tunable materials:

Figure 15 shows several examples of a multi-body carrier 81 comprising at least one body 71 composed of a body suitable for externalizing the dimensions of the body in the direction of the supported portion of the optical fiber when the optical fiber is mounted on the carrier surface. Modulated material. In the embodiment shown in Figures 15.a to 15.h, the carrier comprises two different materials 71,72. Alternatively, the carrier may comprise more than two materials to optimize its properties. For example in the embodiment shown in Fig. 5.g, the 4 parts made of material 172 between the 4 bodies made of material 271 may be made of different materials, for example 2 different from 2 or 4 different. The 4 components made of externally modulatable material (Material 2) 71 can also be different.

Figures 15.a and 15.b show an article 80 with a carrier 81 with a 'strong' convex (semicircle solid, Figure 5.a) and a 'weak' convex (Figure 15.b) carrier surface, wherein the optical fiber 92 is attached to the carrier surface at points 93 on each side of at least one fiber Bragg grating in the optical fiber.

Both embodiments as shown have a generally planar carrier surface 89 opposite a carrier surface adapted to support an optical fiber. This has the advantage that it allows easy placement or assembly of the package in system environments including planar objects (such as most conventional electro-optic system components). One or both side surfaces parallel to the longitudinal direction of the optical fiber (i.e. the outer surface of the carrier or package parallel to the section facing the viewer of Figures 15.a and 15.b) may advantageously be substantially planar In order to facilitate the side assembly on the planar substrate.

The optical fiber may or may not be located in the trench. With the optical fiber 92 in the groove, the convex shape of the carrier surface as shown is the shape of the carrier surface at the bottom of the groove where there is physical contact between the carrier and the optical fiber.

In the semicircular carrier shown in Figure 15.a, two material parts 71 suitable for external modulation are shown, one radially constrained and the other parallel. Alternatively, there may be only one material part 71 present.

FIG. 15 . c shows an article 80 with a carrier 81 and an optical fiber 92 mounted on a convex surface at point 93 . The bottom surface 109 (opposite the carrier surface for supporting the optical fiber 92) has substantially the same shape as the carrier surface. One or both side surfaces 89 parallel to the longitudinal direction of the optical fiber may advantageously be substantially planar in order to facilitate mounting of the sides on a planar substrate.

In the embodiment shown in Figures 15.b and 15.c, the body 71 is located between the center of the carrier and one of the ends of the carrier (ie symmetrical about the center).

Figure 15.d and Figure 15.e show a semicircular carrier and a partially elliptical carrier, respectively. The carrier comprises a body 71 of a material suitable for external modulation, said body being surrounded by another carrier material 72 . At least side surface 89 is substantially planar. In the semicircular carrier shown in Figure 15.d, the adjustable body 71 is located between the center of the carrier and one of the ends of the carrier (i.e. symmetrical about the center), while in the partially elliptical carrier shown in Figure 15.e , the adjustable body is arranged symmetrically about the center of the carrier.

The fundamental resonant frequency can be increased by enclosing the carrier channel compared to the semicircular and partially elliptical embodiments shown in Figures 15.d and 15.e, respectively. Figure 15.f and Figure 15.g show a full ellipse and a full circle carrier, respectively. The full circular carrier shown in Fig. 15.f includes four symmetrically distributed parts made of piezoelectric material 71, for example, while the elliptical carrier shown in Fig. 15.g includes two oppositely arranged on the major axis. part.

By forming grooves in the carrier shown in Figures 15.b to 15.g, it is possible to fix the laser (i.e. the supported part of the optical fiber including the fiber Bragg grating) at the neutral axis (in this case constituting part of the circle). It should be mentioned that for the embodiment shown in Fig. 15.b, the neutral axis may be approximately the neutral axis discussed in Example 2 above. If the cross-sectional area is relatively small relative to the radius of the semi-circular package, the groove depth of the cross-section can be calculated in the same way as for the straight-sided package. The cross-section of the package body in the longitudinal direction perpendicular to the optical fiber (and perpendicular to the plan view shown in Figure 15.a to Figure 15.g) can take any suitable shape, including as shown in Figure 3.a-Figure 3.I the shape shown.

Figure 15.h shows an article 80 comprising a carrier 81 shaped as a solid cylindrical sheet 72, for example made of aluminium, into which a body 71 of an externally modulatable material is inserted In this case, the side surface 89 of the plate carrier is substantially planar and thus suitable for mounting on a planar substrate. The optical fiber 92 can each be located directly on the carrier surface 86 or in a groove. The optical fiber 92 includes a fiber Bragg grating 64 (supported part of the optical fiber) between the fixing points 93 at which the optical fiber is fixed to the carrier surface 86 .

The invention is defined by the features of the independent claims. Preferred embodiments are defined in the dependent claims. Any reference signs in the claims are not intended to limit the scope of the claims.

Some preferred embodiments have been shown above, but it should be noted that the invention is not limited to these embodiments but that it can be carried out in other ways within the subject-matter defined in the following claims.

Claims (62)

1, a kind of optical fiber of the certain-length that is used for laser and goods of packaging body of comprising, described optical fiber comprises the optical fiber Bragg raster above the FBG portion section in the optical fiber that is dispersed in described length, described packaging body comprises the carrier with the carrier surface that is suitable for supporting at least the supported part of optical fiber that comprises FBG portion section, in the use of goods, provide longitudinal tension force thereby described fibre-optic supported part is assembled on the carrier surface and is fixed on the carrier surface of each side of fibre-optic described FBG portion section in fibre-optic supported part, wherein said carrier surface is suitable for keeping convexity in the use of goods.

2, goods according to claim 1, wherein said fibre-optic supported part comprises the optical activity zone.

3, goods according to claim 1 and 2, wherein said carrier have at least one and are suitable for being assembled in outer surface on the flat bearing body.

4, according to each described goods among the claim 1-3, during wherein along the length observation cross section of the supported part of optical fiber, described carrier surface is the part of circle, for example semicircular in shape substantially.

5, according to each described goods among the claim 1-4, wherein said carrier surface is a part that has the cylindrical surface of ellipse or circular cross-section on the preferred general.

6, goods according to claim 5, wherein said cylindrical vector comprises pass through openings.

7, goods according to claim 5, wherein said cylindrical vector surface is the part of solid packaging body.

8, according to each described goods among the claim 1-5, wherein said carrier is elongated.

9, according to each described goods among the claim 1-8, wherein the physics contact channels between supported part of optical fiber and the fibre-optic carrier surface of supporting is a convexity along fibre-optic longitudinal direction.

10, according to Claim 8 or 9 described goods, the supported part of wherein said optical fiber is provided with along the neutral axis of described packaging body substantially.

11, according to each described goods among the claim 1-10, wherein said fibre-optic supported part is provided with along the shear centre passage of described packaging body substantially, makes optical fiber elongation minimum because of the torsional deformation pattern thus.

12, according to each described goods among the claim 2-10, wherein optical fiber Bragg raster completely or partially is set in the fibre-optic optical activity zone.

13, according to each described goods among the claim 2-10, wherein optical fiber Bragg raster is set at fibre-optic optical activity region exterior substantially.

14, according to each described goods among the claim 1-13, the wherein said carrier surface that is used for supporting at least the supported part of optical fiber is arranged in the groove of described carrier.

15, goods according to claim 14, wherein said groove has the square-section.

16, according to claim 14 or 15 described goods, the cross sectional shape of wherein said groove is adapted to the cross sectional shape of described fibre-optic described supported part.

17, according to Claim 8 each described goods-16, when observing in the cross section perpendicular to described fibre-optic longitudinal direction in the time of wherein in being assembled in described groove, described carrier has rectangular substantially external boundary.

18, according to each described goods among the claim 1-17, described fibre-optic supported part in the time of wherein on being positioned at described carrier surface completely or partially is filled material and centers on, described packing material is based on preferably having certain mass density with the described fibre-optic described supported part of same size substantially, for example described fibre-optic mass density 100% with interior, for example 50% with interior, for example 30% with interior, for example 20% with interior, for example in 10%.

19, according to each described goods among the claim 1-18, wherein said carrier comprises pass through openings, and described at least fibre-optic supported part is arranged in described pass through openings.

20, goods according to claim 19, wherein said carrier comprise a plurality of preferred two crew-served bodies, and described pass through openings then is provided when described body is assembled together.

21, according to claim 19 or 20 described goods, wherein said pass through openings has the cross sectional shape that adapts with described fibre-optic cross sectional shape.

22, according to each described goods among the claim 1-21, wherein the curvature of the curve that is limited by the contact channels of described fibre-optic supported part and carrier surface is at 0.004m ^-1To 200m ^-1Scope in, for example at 0.004m ^-1To 20m ^-1Scope in, for example at 0.004m ^-1To 13m ^-1Scope in, for example at 0.004m ^-1To 5m ^-1Scope in, for example at 0.004m ^-1To 2m ^-1Scope in, for example at 0.004m ^-1To 1m ^-1Scope in, for example at 0.004m ^-1To 0.7m ^-1Scope in, for example at 0.004m ^-1To 0.5m ^-1Scope in, for example at 0.1m ^-1To 50m ^-1Scope in, for example at 0.2m ^-1To 2m ^-1Scope in.

23, according to each described goods among the claim 1-22, wherein said carrier surface supports fibre-optic part and has rugged surface, described surface comprises peak portion or spine and recess or paddy portion, wherein when when the longitudinal direction of optical fiber is observed, adjacent peak portion or the distance between the spine are so little, so that be suspended in adjacent peak portion or the fibre-optic eigenfrequency between the spine greater than 5kHz, for example greater than 10kHz, for example greater than 20kHz, for example greater than 25kHz, for example greater than 30kHz.

24, goods according to claim 23, wherein said adjacent peak portion or the distance between the spine are less than 10 millimeters, for example less than 5 millimeters, for example less than 2 millimeters, for example less than 1 millimeter.

25, according to each described goods among the claim 1-24, comprise at least two kinds of materials in the wherein said carrier.

26, goods according to claim 25, wherein said carrier comprise second body that at least one is made by a kind of material, and its longitudinal size is suitable for carrying out external modulation specially.

27, goods according to claim 26 comprise a kind of material in wherein said second body, and its longitudinal size is suitable for carrying out electrical modulation specially.

28, according to each described goods among the claim 26-27, comprise piezoelectric in wherein said second body.

29, goods according to claim 28, wherein said piezoelectric is selected from following material group, comprises piezoceramic material such as polycrystalline ferroelectric ceramic material in the described material group, for example barium titanate and lead zirconate titanate (PZT) and combination thereof.

30, according to each described goods among the claim 25-29, wherein said carrier comprises first body of being made by a kind of material, and the longitudinal size specific adaptation of described carrier is in carrying out the heat modulation.

31, goods according to claim 30 wherein constitute along the material coefficient of thermal expansion factor alpha of described first body of the longitudinal direction of carrier _T-1Equal to constitute the material coefficient of thermal expansion factor alpha of described second body substantially _T-2

32, goods according to claim 30 wherein constitute along the material coefficient of thermal expansion factor alpha of described first body of the longitudinal direction of carrier _T-1Greater than the material coefficient of thermal expansion factor alpha that constitutes described second body _T-2, for example greater than α _T-21.5 times, for example greater than α _T-22 times, for example greater than α _T-25 times.

33, according to each described goods among the claim 30-32, comprise the material that is selected from the following material group in wherein said first body, comprise metal such as aluminium or copper or its alloy, ceramic material and combination thereof in the described material group.

34, according to each described goods among the claim 30-33, wherein said first body has constituted the main volume of described carrier.

35, according to each described goods among the claim 26-34, wherein said second body or a plurality of described second body are provided with respect to the carrier cross section perpendicular to the place, centre position of its longitudinal direction between the longitudinal end of described carrier asymmetricly.

36, according to each described goods among the claim 26-34, wherein said second body or a plurality of described second body are provided with symmetrically with respect to the carrier cross section perpendicular to the place, centre position of its longitudinal direction between the longitudinal end of described carrier.

37, according to each described goods among the claim 1-36, wherein said fibre-optic supported part comprises two optical fiber Bragg rasters that spatially are spaced.

38, according to each described goods among the claim 1-37, comprise the DBR laser, wherein said optical fiber and described optical fiber Bragg raster have formed the described DBR laser of part.

39, according to each described goods among the claim 1-37, comprise Distributed Feedback Laser, wherein said optical fiber and described optical fiber Bragg raster have formed the described Distributed Feedback Laser of part.

40, according to each described goods among the claim 1-39, wherein said optical fiber is based on the optical fiber of silicon dioxide.

41, according to each described goods among the claim 1-40, wherein said optical fiber comprises the microstructure that extends longitudinally.

42, according to each described goods among the claim 1-41, wherein said optical fiber is the double clad optical fiber.

43, according to each described goods among the claim 1-42, wherein the curve that is limited by the contact channels of described fibre-optic described supported part and described carrier surface is substantially the part of the circle with radius R, described carrier has longitudinal tensile strain amount L, described Bragg grating has grating intensity κ, described carrier has neutral axis N, wherein for κ L greater than for 1 the situation, in the lateral cross section at the place, centre position between the described longitudinal end of described carrier, the distance h between described circle and the described neutral axis equals (4R κ) substantially ^-1

44, according to the described goods of claim 43, wherein κ L is greater than 2, for example greater than 5, for example greater than 10.

45, according to claim 43 or 44 described goods, wherein in the lateral cross section at place, the centre position between the described longitudinal end of described carrier, the distance h between described circle and the described neutral axis equals 0 substantially.

46, a kind of equipment that comprises according to each described goods among the claim 1-45.

47,, constitute lidar light detection and ranging (LIDAR) system or interferometer measuration system or become the part of described system according to the described equipment of claim 46.

48, according to the application of each described goods among the claim 1-45.

49, according to the described application in lidar light detection and ranging (LIDAR) system or interferometer measuration system of claim 48.

50, a kind of manufacture method of goods said method comprising the steps of:

(a) be provided for the optical fiber of the certain-length of laser, described optical fiber comprises and is used for optical fiber Bragg raster that the light wavelength of conducting at described optical fiber is selected, described optical fiber Bragg raster is dispersed on the fibre-optic FBG portion section of described length

(b) be provided for supporting described fibre-optic carrier, described carrier comprises:

Be used for supporting at least the carrier surface of described fibre-optic supported part,

(b1) make described carrier surface be adapted such that described fibre-optic described supported part and the physics contact channels of supporting between the described fibre-optic described carrier surface on the described fibre-optic longitudinal direction be convexity and be suitable for keeping convexity in the use at described goods, and

(c) described fibre-optic described supported part is assemblied on the described carrier surface of the described fibre-optic described FBG portion section that comprises described length at least, so that described supported part is fixed on the described carrier surface, thereby in the use of described goods, in described fibre-optic described supported part, provide longitudinal tension force on each side of described fibre-optic described FBG portion section.

51,, further comprise making described packaging body be suitable for machinery (for example sound) vibration from environment is reduced to minimum step according to the described method of claim 50.

52, according to claim 50 or 51 described methods, wherein step (b) further comprises the step (b2) that makes described carrier comprise at least two bodies being made by different materials.

53, according to each described method among the claim 50-52, wherein step (b) further comprises the step (b3) that described carrier is comprised be suitable for carrying out along the longitudinal size of described carrier the material of external modulation.

54, according to each described method among the claim 50-53, wherein step (b) comprises that further described different materials is comprised to be suitable for carrying out heat first material of modulating and the step (b4) that is suitable for carrying out along the longitudinal direction of described carrier second material of external modulation along the longitudinal direction of described carrier.

55, according to each described method among the claim 50-54, wherein step (b) comprises that further described carrier is comprised has the step (b5) that is suitable for being assembled at least one outer surface on the flat bearing body.

56, according to each described method among the claim 50-55, wherein said method further may further comprise the steps:

(d1) curve that the contact channels by described fibre-optic described supported part and described carrier surface is limited is substantially the part of the circle with radius R, and makes described carrier have longitudinal tensile strain amount L,

(e1) make described Bragg grating have grating intensity κ,

(f1) determine the neutral axis N of described carrier,

(g1) make for κ L greater than for 1 the situation, in the lateral cross section at the place, centre position between the described longitudinal end of described carrier, the distance h between described circle and the described neutral axis equals (4R κ) substantially ^-1

57, according to the described method of claim 56, wherein step (g1) is by making that in the lateral cross section at the centre position place between the described longitudinal end of described carrier, the distance h between described circle and the described neutral axis equals 0 step (g2) replacement substantially.

58, according to each described method among the claim 50-57, wherein step (a) further is included in the step (a1) that forms the optical activity zone in the described fibre-optic described supported part.

59, according to the described method of claim 58, wherein step (a1) further comprises the step (a1.1) that described optical activity spatial extension scope regional and described optical fiber Bragg raster is overlapped wholly or in part.

60, according to the described method of claim 58, wherein step (a1) further comprises the step (a1.2) that described optical activity zone is not overlapped with the spatial extension scope of described optical fiber Bragg raster substantially.

61, according to each described method among the claim 50-60, wherein step (a) further comprises and makes described fibre-optic described supported part comprise at least two independently fibre-optic steps (a2) of certain-length, described at least two independently the optical fiber of certain-length carry out light each other and connect, for example engage.

62, according to the described method of claim 61, wherein step (a2) further is included in the step (a2.1) that forms described optical fiber Bragg raster in the optics passive fiber of certain-length.

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