WO2000037980A1 - Coil form for quickly unwinding an optical fibre and output device for an optical fibre - Google Patents

Abstract

The invention relates to a coil form (1) for quickly unwinding an optical fibre (14) for transmitting data between a moving object and a control station. Said coil form (1) comprises a guide cylinder (12) on which a support roller (13) is mounted in an axially moveable or sliding manner. The guide cylinder (12) has a thermal expansion coefficient which is adapted or corresponds to the thermal expansion coefficient of a glass body which is arranged in the optical fibre (14). The support roller (13) has a thermal expansion coefficient which corresponds or is approximated to the mean thermal expansion coefficient of the optical fibre (14) which is embodied as a winding unit (2). The movement of the outer surface of the coil form (1) is adapted to the anisotropic thermal behaviour of the winding unit (2) when there is a change in temperature. The support roller (13) has a longitudinal slit and is connected to the guide cylinder (12) via a fixing element (15). Displacement of the windings of the optical fibre (14) and tensions and fractures due to variations in temperature are avoided and the security of data transmission is guaranteed.

Description

 Bobbin for the rapid unwinding of an optical fiber and output device for optical fibers

The present invention relates to a coil former for quickly unwinding an optical waveguide and an output device for optical waveguides.

To exchange navigation data, it is often necessary for vehicles or

Aircraft are connected to a steering point even after takeoff. This can e.g. B. in a guided missile by an optical transmission chain.

An optical waveguide, which is wound on a coil former, is usually used for this. For the purpose of data transmission between a vehicle and a remote location, the optical fiber is unwound from a container.

This can z. B. on a rocket, a missile, an aircraft, an object in the air, a land vehicle, a watercraft or an underwater device.

Such output devices, which are constructed from the coil former and from an optical waveguide in the form of a winding package, must be able to extend the optical waveguide over very long lengths, e.g. B. can be 60 km and more to handle at very high speeds. Very high demands are also placed on the strength of the winding package, in order, for. B. not to be destroyed or damaged in the event of vibrations or a mechanical or thermal shock, so that a functional failure occurs when the coil is unwound. In order to give the winding package the necessary strength, the individual turns and the layers are glued together when winding the coil body. In addition to the increased strength, the gluing should also avoid that several turns or layers are pulled out simultaneously when the optical waveguide is quickly pulled off. This would lead to the fiber optic being torn off and the system failing.

The optical waveguide or the optical fiber essentially consists of a glass body for guiding the light and a coating or plastic coating. The coating serves to protect the vitreous from physical or chemical influences and reduces the microbending, ie the attenuation of the light passed through the optical waveguide due to partial pressures on the optical waveguide. The coating can consist of one or more layers of different types of plastic, which are usually very soft types of plastic. Today, mostly optical fibers with a glass diameter of approx. 125 μm and a total diameter of approx. 250 μm are used.

However, there is the problem that with temperature fluctuations, the z. B. can occur on ^¬ due to different climatic conditions, the winding package may occur stresses or cracks. The different thermal expansion coefficients of the coil body on the one hand and the winding package on the other hand can also lead to displacement or loosening of turns and thus to failure of the system.

No. 4,995,698 proposes a solution to the problem

Output device for an optical waveguide to be provided with a bobbin, which is made of an orthotrophic composite material, so that the thermal expansion coefficient of the bobbin corresponds in the circumferential direction to the thermal expansion coefficient of the optical fiber in the longitudinal direction and the axial thermal expansion coefficient of the bobbin corresponds to the lateral thermal expansion coefficient of the optical fiber. In practice, however, it is difficult and expensive to provide a suitable ortotrophic material which meets the high requirements.

EP 0616 237 B1 therefore proposes to provide the coil with a heating device which is connected to a power or heat supply. This is intended to keep the output device with the coil and the winding package within narrow temperature limits, so that the thermal contraction or expansion of the coil body and the optical fiber are limited. However, this system is very complex, since an additional energy supply is required in the output device carried by the missile. In addition, in the event of extreme climatic temperature fluctuations, a very high output and an extremely precise adjustment of the heating output before and after the start are required in order to maintain a constant temperature maintain. Further disadvantages of this solution are that the device cannot be used immediately due to a necessary heating-up time, there is an additional space and energy requirement, and possible damage to the winding package during cooling due to different thermal expansion between the coil former and the winding package. In addition, there is no possibility of compensation when used under elevated temperatures.

It is therefore the object of the present invention to provide a coil former for the rapid unwinding of an optical waveguide and an output device for an optical waveguide which ensures sufficient strength of the winding package over a wide temperature range and can be produced inexpensively using the materials which are usually used.

This object is achieved by the bobbin according to claim 1 and the output device according to claim 13. Further advantageous features, aspects and details of the invention result from the dependent claims, the description and the drawings.

The bobbin according to the invention for the rapid unwinding of an optical waveguide comprises at least two cylinders which have a different coefficient of thermal expansion, the thermal expansion coefficient of the first cylinder being adapted in the radial direction to the thermal expansion coefficient of a light-guiding part or glass body of the optical waveguide to be unwound from the coil former and the coefficient of thermal expansion of the second cylinder is adapted in the axial direction to the average coefficient of thermal expansion of the optical waveguide. This ensures that the bond between the windings and between the layers of the winding package is not torn open when the ambient temperature changes. Crack formation is prevented without the need for special materials or additional power supply or heating devices. A stable unwinding of the optical waveguide is guaranteed over a high temperature range, which increases the security of the system. The second cylinder may have one or more slots in the axial direction, the width of the slot advantageously being selected such that it is just closed at the highest possible temperature of the coil system. Through the slot can be a simple. achieve particularly good adaptation of the expansion behavior of the coil body to the expansion behavior of the winding package. The second cylinder or supporting cylinder is preferably slidably slidable on the first cylinder or guide cylinder, wherein a sliding layer, such as silicone, graphite or the like, is advantageously located between the supporting cylinder and the guide cylinder. The first cylinder z. B. movably connected in the axial direction to the second cylinder. The second cylinder is advantageously fixed to the first cylinder at points or along a line. By adjusting the play between the two cylinders or by sliding the support cylinder in the axial direction on the guide cylinder, the different thermal expansions of the support and guide cylinders that occur in the event of temperature changes are also compensated in an excellent manner in the axial direction.

The second cylinder can have a cylindrical or conical surface for winding with the optical waveguide, which is preferably provided with parallel grooves or with a helical groove. This ensures that the first layer of the turns of the optical waveguide sits stably on the coil former due to its inclusion in the groove, whereby the strength of the winding package against shifting of turns is further increased. The surface of the second cylinder for winding with the optical waveguide can also be wound with one or more layers of a material with a similar diameter and in the same arrangement as the optical waveguide. One or more first layers on the support cylinder, which do not have the function of signal transmission but are used as blind layers, can further increase security.

The second cylinder is advantageously designed in such a way that it has a thin wall in relation to the first cylinder or is thin-walled. This also results in a particularly good adaptation of the coil body to the winding package in the event of temperature fluctuations. The first and / or the second cylinder can e.g. B. made of metal, ceramic, plastic or a combination of the materials. The output device for optical waveguides according to the invention comprises a winding package consisting of an optical waveguide and the coil former according to the invention, which carries the winding package.

The present invention is described below with reference to the figures in which

Figure 1 shows a first embodiment of the bobbin according to the invention with a support and a guide cylinder;

Figure 2 shows schematically a cross section through a support cylinder with a continuous slot;

Figure 3 shows a schematic representation of a conical bobbin according to another embodiment of the present invention;

Figure 4 shows a schematic section of a longitudinal section through a

Coil former according to yet another embodiment of the invention;

Figure 5 is a schematic diagram of an output device for

Optical fiber in a longitudinal section shows; and

FIG. 6 shows the structure of an optical waveguide as it is from the invention

Coil body or the output device is worn in operation.

FIG. 1 shows a cylindrical coil former 1 with different coefficients of thermal expansion in the radial and axial directions as the first preferred embodiment of the invention. The bobbin 1 has a guide cylinder 12 on which a support cylinder 13 is seated. The support cylinder 13 is arranged on the guide cylinder 12 so that its inner surface slides on the outer surface or outer peripheral surface of the guide cylinder 12. Between the sliding surfaces of Guide and support cylinder is introduced with a lubricant, such as. B. silicone, graphite or the like. The two cylinder elements 12, 13 are point-connected to one another via a fixation 15. The support cylinder 13 can also be connected to the guide cylinder 12 along a diameter line. The coil former 1 serves to receive an optical waveguide 14 or an optical fiber with a core made of glass, which is surrounded by a coating or plastic coating, in the form of a winding package 2. The area. of the bobbin 1, which serves to receive the winding package 2, consists of two parts, as shown in Figure 1. The two parts of the coil former 1 have different coefficients of thermal expansion. The coefficient of thermal expansion of the guide cylinder 12 corresponds to that of the glass body of the optical waveguide or is adapted or approximated to this. The support cylinder 13 is made of a material whose coefficient of thermal expansion is adapted to, or approximates, the average coefficient of thermal expansion of the optical waveguide 14.

The support cylinder 13 is designed as a thin shell, i. H. its wall thickness is small compared to that of the guide cylinder 12. The support cylinder 13 has a continuous longitudinal slot 25, as shown in Figure 2. The slot width b is kept as small as possible and is designed so that the slot 25 at the upper corner temperature of the system, i. H. is just closed at the highest possible temperature to be expected of the coil system, so that b = 0.

The different thermal expansions of the support and guide cylinders are compensated in the axial direction due to the sliding guidance of the support cylinder 13 on the guide cylinder 12 or due to the play adjustment. The different thermal expansions of the two cylindrical elements 12, 13 are compensated in the radial direction by the slot 25 in the support cylinder 13, which increases or decreases as the temperature changes. Overall, the outer surface of the coil former 1, on which the optical waveguide 14 is wound, has the thermal expansion coefficient 0.5z of the support cylinder 13 in the axial direction and the thermal expansion coefficient z of the guide cylinder 12 in the radial direction. Since the coefficient of thermal expansion α _{Z of} the guide _{cylinder 12} approximates or corresponds to the coefficient of thermal expansion OQ \ _ΆS , the coil former has a coefficient of thermal expansion α $ κ _r in the radial direction which approximates or corresponds to that of glass, ie “SK. r S CXGlas (•) ^■

The thermal expansion coefficient of the coil former 1 in the axial direction α _S κ _{, z} , on the other hand _, corresponds to the thermal expansion coefficient αsz of the support cylinder 13, which is approximated to the average thermal expansion coefficient of the winding package 2 in the Z direction, ie in the axial direction, or corresponds to it, ie it applies :

α _S κ, z ≡ α _z (2).

This average coefficient of thermal expansion of the winding package 2 in the longitudinal or Z direction results from the equation

(^ L ^{_ <} ^ GIas) ^α coatιnε + ^ glass ^' ^ glass (3), α _z = ^υ fiber

where d L is the outer diameter of the optical waveguide and d G _{las is} the diameter of the glass body of the optical waveguide. In the currently mainly used optical waveguides in telecommunications, d _L WL is 250 μm and d _G i _as 125 μm, ie in this case the outer diameter d W _{L of} the optical waveguide 14 is twice as large as the diameter d oias of the glass body. With this ratio of diameters, the average coefficient of thermal expansion of the optical waveguide 14 or of the winding package 2 in the Z direction results

^α Z ⁼ l ^α glass ^{+ U} coating)

2 (4). For other diameter ratios, factor V2 in equation (4) must be adjusted accordingly.

This anisotropic behavior of the winding package 2 results from the following consideration. The expansion behavior of the winding package 2 in the event of a change in temperature can generally be described as follows:

If an elongated optical waveguide of length I undergoes a temperature change by ΔT, its length changes by Δl, where

Δ l = α _f ΔT (5).

^ Glass

Here αoi- _s is the linear thermal expansion coefficient of the glass used. The soft coating of the optical fiber is insignificant and adapts to the length of the glass. If the glass is placed in a ring, ie on one

Coil body wound, so there is a change in the diameter d of the winding of at a temperature change ΔT

Δ d, = d α _glass - ΔT ₍₆₎ .

Even if an entire layer is considered, which can consist of several hundred turns, equation (6) also applies to the radial expansion. The expansion behavior of the glass is forced on the coating.

In the axial direction or in the Z direction, ie along the longitudinal axis L of the coil, however, there is a different behavior, since the coefficient of thermal expansion of glass is very much smaller than that of the coating in the optical waveguides currently used. Here the glass only acts like a spiral spring, ie the coating that expands more expands the glass when the temperature is raised. If the temperature is reduced, this spiral spring is shortened. In other words, in the axial direction or in the Z direction, the expansion behavior of the winding package 2 is determined by the thermal expansion coefficient of the coating and the glass. The middle one The coefficient of thermal expansion of the optical waveguide 14 laid in turns in the Z direction results in a good approximation according to equation (3) listed above.

As shown above, the thermal expansion coefficient of the winding package is anisotropic. The following applies to the change in length and the change in the diameter of the winding package:

Δl winding package ⁼ 'winding package ^{' ö} z ^'Δ (7a)

Δd _{W | Cke | pake} , = d _Wlcke | _{package | inner} ' ^α glass ^{' l} (7b)

By means of the present invention, the coil former 1 is adapted to the anisotropic thermal expansion behavior of the winding package 2. If the temperature of the system, for example, lowered so, the winding package 2-pulling direction Z in order to _bridge ΔLwi i _package according to the above equation (7) together, and is carried out in the radial direction

Reduce the diameter by Δdwic eipa et according to equation (7b) above. Since the coil former 1 is constructed from two nested cylindrical elements 12, 13, which have the thermal expansion coefficients αoi _as and αz defined above, the movement of the surface of the coil former 1 is adapted to that of the winding package 2 when the temperature changes. Therefore, tensions in the winding package 2, which could lead to tears, are avoided and friction between the layers is prevented. The adhesive connections remain stable and the security of the system is guaranteed.

The coil former 1 behaves as follows when the temperature changes ΔT:

The diameter Dp of the guide cylinder 12 changes according to the equation

ΔD _F - D _F - α _glass - ΔT (8) and the wall thickness a of the support cylinder 13 changes according to the equation

Δa = a - α _sz ΔT (9)

This results in 1 ΔD _S = ΔD _F + 2 Δa for the mean change in diameter ΔDs of the coil former

ΔD _S = (D _F - α _glass + 2a - α _sz ) ΔT (10). The change in the inner diameter D \ of the winding package 2 results with a sufficient approximation

_k D, = D _{W l} - α _glass - ΔT D α glass ΔT (1 1)

where D $ denotes the mean diameter of the coil body. The relative

Error F when changing the inner diameter of the winding package ΔDy ^ /, and changing the outer diameter of the bobbin Ds results accordingly

d h der Spulenkorper 1 ist so auszulegen, daß der relative Fehler F gegen 0 geht.

ie the bobbin 1 is to be designed so that the relative error F goes to 0.

When selecting the material of the support cylinder 13 which is as thin-walled as possible, care must be taken that the coefficient of thermal expansion α $ z of the support cylinder 12 is by no means greater than aχ, since in general a is greater than αQ _{| as}

αsz ^{≤ (} * z (13)

With short coil lengths, the values in this inequality can deviate more than with large lengths. The absolute error is then not too big

FIG. 3 shows a further embodiment of the coil former according to the invention, which has different coefficients of thermal expansion in radial and axial directions In this case, a support cylinder 23 is arranged on the guide cylinder 12 with a conical or tapered jacket surface 23a, which serves to support the turns of the optical waveguide 14. The fixation 15 can be arranged at any point. Also in this embodiment with a conical coil body 1, which, as described above, is made up of two elements 12, 23 with different coefficients of thermal expansion, the thermal behavior of the coil body 1 is adapted to the anisotropic thermal behavior of the winding package 2.

The guide cylinder 12 is screwed on one side directly to a flange, which is not shown in the figures. However, the flange can also be connected to the guide cylinder 12 by another connection technique. It is also made of a material whose coefficient of thermal expansion approximates or corresponds to that of glass.

4 shows the surface of a support cylinder 33 in accordance with a further embodiment of the invention in an enlarged, partial longitudinal section. The circumferential or jacket surface of the coil former 1 or support cylinder 33 is provided with grooves 38 which act as a guide for the optical fiber to be wound or unwound 14 serve instead of grooves, a spiral-like groove in the surface 23a of the support cylinder 33 can also be designed as a guide for the optical waveguide 14. As a result, the optical waveguide 14 is secured even better against slipping or damage due to tension or friction

In general, the outer surface of the support cylinder 13, 23, 33 can thus be cylindrical, conical, smooth or provided with grooves

In a further embodiment, not shown here, the first two layers wound on the support cylinders are designed only as blind layers, ie they do not have the function of a signal transmission between a steering point and the moving object. This ensures a particularly high level of security and stability of the data transmission, since any stress that may still occur in the lowermost layers does not impair the signal transmission The support cylinder can also be constructed from several parts and z. B. include several shells, which can be obtained in particular by multiple slits.

FIG. 5 schematically shows a longitudinal section through an output device for optical fibers according to the invention. The output device consists of a coil former 1 according to the invention, as described above. The winding package 2, which is formed from a multiplicity of layers of the optical waveguide 14, is arranged on the conical outer surface of the coil former 1. In order to achieve the necessary stability and strength, which must be designed for very heavy loads during the rapid unwinding of the optical waveguide 14, the individual layers of the optical waveguide 14 are glued together. A flange 50 is arranged on the end face of the coil former 1. Coil body 1 and winding package 2 form a coil which is arranged in a sheath 3. The withdrawal direction for the optical waveguide 14 is indicated in FIG. 5 by the arrow A and runs in the direction of the Z axis. The trigger device according to the invention with the bobbin described above ensures safe and stable carrying and pulling or unwinding of the optical waveguide 14, even at the extremely high speeds such. B. a rocket, which carries the output device or the payout system and is connected to a steering station on the ground when flying through the optical fiber. Even with large temperature changes, such as. B. occur in extreme climatic conditions, the stability of the turns and thus the security of data transmission is guaranteed due to the invention.

FIG. 6 shows a cross section of an optical waveguide, as is used in connection with the present invention, in a schematic representation. The optical waveguide 14 has a glass body 14a in its interior, which is surrounded by a coating 14b, which can consist of several layers. In the center of the glass body 14a, a mode field 14c is formed as the actual light-guiding core.

Claims

IPatent claims 1. coil former (1) for the rapid unwinding of an optical waveguide (14), characterized in that the coil former (1) has at least two cylinders (12, 13, 23, 33) which have a different coefficient of thermal expansion, the coefficient of thermal expansion of the first cylinder (12) being adapted in the radial direction to the coefficient of thermal expansion of a light-guiding part (14a, 14b) of the optical waveguide (14) to be unwound, and the coefficient of thermal expansion of the second cylinder (13, 23, 33) in axial Direction is adapted to the average coefficient of thermal expansion of the optical waveguide (14) 2. Bobbin according to claim 1, characterized in that the second cylinder (13, 23, 33) has a slot (25) in the axial direction 3. bobbin according to claim 2, characterized in that the width of the slot (25) is selected so that it is just closed at the highest possible temperature of the bobbin 4. Bobbin according to one of the preceding claims, characterized in that the second cylinder (13, 23, 33) slidably sits on the first cylinder (12) 5. Bobbin according to one of the preceding claims, characterized in that there is a sliding layer between the first (12) and the second cylinder (13, 23, 33) 6. Bobbin according to one of the preceding claims, characterized in that the first cylinder (12) is movable in the axial direction with the second Cylinder (13, 23, 33) is connected 7. Bobbin according to one of the preceding claims, characterized in that the second cylinder (13, 23, 33) is fixed at certain points or along a line on the first cylinder (12) 8. Bobbin according to one of the preceding claims, characterized in that the second cylinder (13, 23, 33) is cylindrical or conical. Surface for winding with the optical fiber (14) 9. Bobbin according to one of the preceding claims, characterized in that the second cylinder (33) has a surface (23a) for winding with the optical waveguide (14), which is provided with parallel grooves (38) or with a helical groove 10. Bobbin according to one of the preceding claims, characterized in that the surface of the second cylinder (13, 23, 33) for winding with the optical waveguide (14) with one or more layers of a material with a similar diameter and in the same arrangement how the optical fiber (14) is wound 1 1. bobbin according to one of the preceding claims, characterized in that the second cylinder (13, 23, 33) in relation to the first cylinder (12) is thin-walled 12. Bobbin according to one of the preceding claims, characterized in that the first (12) and / or the second cylinder (13, 23, 33) Metal and / or ceramic and / or plastic is made 13. Output device for optical fibers with a winding package (2) made of an optical fiber (14), characterized by a coil former (1) according to one of the preceding claims, which carries the winding package (2)