HK1066280B - A terminus for a fiber-optic cable and its manufacturing method, a fiber-optic cable connector and a method of aligning and connecting fiber-optic cables - Google Patents

Description

Optical fiber cable terminal device, manufacturing method thereof, optical fiber cable connector and optical fiber alignment connection method

Technical Field

The present invention relates to electro-optical converters and optical transmission devices, in particular to luminescence detection converters and optical transmission systems thereof, and to devices and methods for aligning such systems and converters. The present invention also relates to fiber optic cables, and more particularly to terminations, connectors, alignment devices, and optical systems and methods for terminating fiber optic cables.

Background

The provision of optical transmission systems in use of electro-optical converters has long been problematic, particularly in communication systems where the transmission is by optical fibre cables.

The coupling of the electro-optical transducer has been complicated by the extremely small diameter of the transmitted beam and the small size of the semiconductor devices often used to generate or detect the signal. Any foreign matter such as dirt and dust that accumulates on the signal optical path can seriously compromise the integrity and operability of the system.

The difficulty of using fiber optic cables for transmission is also well known. For example, it has been a demanding problem to provide appropriate terminations and connectors to connect two fiber optic cables together. This problem is exacerbated by the widespread use of single mode optical light guides, such as those having very small diameters of 8 microns (0.008 meters). Precise alignment of fiber optic cables is often a time consuming and rigorous process.

There are a number of problems associated with standard commercial butt-type single mode fiber optic connectors. First, they are relatively delicate, messy, difficult to clean, and easily damaged. These problems are even more acute for multi-channel connectors that must operate in harsh environments.

In the past, many proposals have been made to improve upon such existing connectors, including proposals to use a flared connector. Such connectors use different types of lenses to collimate and propagate the light beam emitted by the light guide. An identical lens system is then used to terminate the end of another cable to be coupled to the first cable and to connect the two ends together. The second lens system refocuses the light beam onto the second light guide to transmit the signal through the second cable.

The optical system for such existing beam expanding type connectors includes a spherical lens, a "GRIN" lens (graded refractive lens), and a molded aspherical lens for expanding and collimating a beam.

Advantages of such a spread-beam connector include minimizing susceptibility to contamination and lateral misalignment, and minimizing the size of the gap between the ends of the light guides.

However, there are several problems with existing expanded beam connectors and techniques. These problems include high optical losses and high costs. In fact, such costs have been considered a limiting condition for many commercial applications. Furthermore, existing designs are considered difficult or simply impossible to install properly in the field, i.e., outside of a factory, laboratory or other such facility.

Disclosure of Invention

It is therefore an object of the present invention to provide an electro-optical transducer device and an optical fibre cable termination device, connector and coaxial alignment device and method which overcome or mitigate the above problems.

In particular, it is an object of the present invention to provide a spread beam termination and connector and coaxial alignment apparatus and method that overcome or mitigate the problems encountered with prior spread beam devices.

In particular, it is an object of the present invention to provide an electro-optical transducer and a fibre optic cable termination device and connector which have as many advantageous properties as possible: the LED lamp has the advantages of low cost, low loss, low back reflection, small size, firmness, durability, difficult dirt, easy cleaning, field installation and higher optical power transmission capability; the device is suitable for severe environments; it can be standardized.

It is an object of the present invention to provide such an apparatus and method that can operate with single mode light guides and multi-channel cables that are non-dichroic and preserve the polarization of the transmitted light guide.

It is an object of the present invention to provide an integrated multi-reflector optical device for expanding and collimating light beams, and particularly fiber optic cable light beams.

According to the present invention, the above object is achieved by providing an electro-optical converter having an input/output optical transmission system in which the output is propagated by means of a dual reflector optical system, which system avoids the problem of using refractive means therefor. The dual reflector system is preferably coupled to the converter directly or via an optical guide such as a fiber optic cable. Preferably, the elements are aligned with each other by coupling one of the fiber optic conductor and the dual reflector system to a magnetically permeable member and using magnetic flux to move the elements.

The objects of the present invention relating to fiber optic cables are also achieved by providing a fiber optic cable termination device, connector and alignment device and method as described below.

The present invention provides an optical fiber cable terminal device, comprising: a housing for supporting and holding an optical fiber conductor having a distal end; a first reflector secured to said housing and positioned to receive and reflect light emitted from said distal end; a second reflector secured to said housing and positioned to receive light reflected by said first reflector and project said light in the form of a collimated beam having a diameter substantially greater than the diameter of light emitted from said end; a magnetically permeable element positioned within the housing and responsive to an external magnetic field to move the tip laterally.

The present invention also provides an optical fiber cable connector comprising: an elongated tubular housing, the ends of the two fiber optic cables extending into opposite ends of the housing and the ends being adjacent to each other; an element made of magnetically permeable material positioned within the housing and coupled to at least one of the ends for moving the end in response to an external magnetic field, the housing capable of receiving curing radiation, and the end of the fiber optic cable embedded in a mass of radiation curable epoxy.

Further, the present invention provides an optical fiber cable terminal device, comprising: a housing for supporting and holding an optical fiber conductor having a distal end; a first reflector secured to the housing and positioned to receive and reflect light emanating from the distal end; a second reflector secured to the housing and positioned to receive light reflected from the first reflector and project the light in the form of a collimated beam having a diameter substantially greater than the diameter of the light emanating from the end; the first reflector and the end of the optical fiber conductor are located outside the optical path of light rays reflected by the second reflector, the end and the second reflector being substantially aligned with the second reflector positioned between the end and the first reflector.

The present invention provides a method for connecting two fiber optic cables together and coaxially aligning the ends of two fiber optic conductors in the cables with one another, comprising: a) inserting the ends into a housing having a body of magnetically permeable material connecting at least one of the ends; b) moving the body of magnetically permeable material laterally by magnetic force until the ends are aligned with each other; c) with the conductor ends aligned with each other, the ends are secured together by a radiation curable plastic.

The present invention also provides a method of manufacturing an optical fiber cable termination device, comprising the steps of: a) providing a ferrule having a first chamber for a lens system and a cable receiving tube leading to said first chamber via a second chamber; b) positioning a magnetically permeable element within said second chamber, said magnetically permeable element having a central bore for receiving an end of said cable; c) installing the lens system within the first chamber; d) introducing a hardenable liquid radiation curable plastic into the second chamber; e) inserting a cable end into the magnetically permeable element through the central bore; f) applying a magnetic force to the magnetically permeable element to align the cable end with the lens system; and g) hardening the liquid radiation-curable plastic to fix the position of the cable end.

In the converter arrangement and the fibre-optic cable termination arrangement, the reflector system is preferably similar to a cassegrain (cassegrain) or a richcketisin (Ritchey-Chretien) transmitting telescope system. Such systems have been used in the field of astronomy for many years. The applicant has appreciated that although telescope systems are typically large and expensive, it is possible to make smaller devices for the present invention that are less expensive. The use of reflectors or mirrors rather than lenses tends to minimize the refractive effects that often make the optical design procedure proposed by the generally known art for expanded beam connectors difficult. The resulting optical system is very compact, relatively easy to standardize and inexpensive to manufacture.

According to another feature of the present invention, the problem of aligning a transducer or light guide in a fiber optic cable is completely alleviated by coupling a magnetically permeable member to the object to be aligned, applying a magnetic field to the magnetically permeable member and controlling the extent to which the objects move and align with each other. Movement in at least two orthogonal axes is preferred.

Proper alignment is tested by passing a signal through the conductor and the second conductor and determining when the signal is transmitted to a maximum value. Additionally, or alternatively, the alignment may be visually performed by looking through the exit of the reflector system with a microscope or other viewing device to detect the source point, i.e., the termination of the fiber optic cable connector or the transducer input/output port, etc.

The source point is preferably observed using a camera with a zoom microlens. The image of the source point is displayed along with a target and alignment is achieved using a position adjustment system.

The light guide and other components are then fixed in position relative to each other. This is preferably achieved by injecting a radiation curable plastic such as epoxy into the area around the component and, when properly aligned, irradiating the material to harden it. In particular, one embodiment of the present invention uses a photocurable epoxy resin. Light is directed at the epoxy to effect curing.

The magnetic field source is also preferably used to generate a rotating magnetic field that rotates about the object to be aligned, and an electrical grid is provided to control the magnetic field. This allows the effective center of the magnetic field to be moved and the object being aligned to be accurately positioned.

In a preferred embodiment, the magnetically permeable element is approximately annular or cylindrical with a truncated conical entrance to the central opening to guide the conducting fiber into the central opening during installation.

The present invention also provides a dense optical device that disperses and collimates light. A piece of transparent material such as glass or plastic has surfaces of the reflector shaped to the desired size, shape and location, and those surfaces are then coated with a reflective material such as metal. This can be done by vapor deposition, sputtering, etc. in a reasonably cost manner.

Problems often encountered when splicing together the two ends of an optical fiber cable are: the problem of back reflection of signals occurs at the glass fiber-air interface between the ends of the cable cores. In the past, this problem has been solved using various techniques: if the tail end of the fiber is in a circular arc shape; making the ends very flat and butting the ends together to eliminate air gaps; the air gap is filled with an index matching gel or the like. However, these methods have drawbacks.

It is believed that the interface between air and the exit face of the integrated emitter unit of the present invention has the same back emission problems as any other light-transmissive solid-air interface. It is therefore another object of the present invention to suppress this back reflection without the disadvantages of the previous methods.

According to another aspect of the invention, the beam-diverging output face of the light delivery block is given a slight curvature so that the reflected beam is reflected along a different path than the path traveled by the collimated and focused light rays, thereby suppressing reflections. Therefore, they are largely unable to reach the source point and are thus suppressed. As a result, a higher degree of inhibition is achieved without the use of gels or other known techniques.

If desired, the wide input/output face of the light delivery block may also have an anti-reflective coating to help suppress reflections.

The foregoing and other objects and advantages of the invention will be apparent from or elucidated with reference to the following description and drawings.

Drawings

FIG. 1 is a cross-sectional view of a fiber optic cable termination device constructed in accordance with the present invention;

FIG. 2 is a perspective view of a system and method for aligning the light guides of the cable shown in FIG. 1;

FIG. 3 is a schematic diagram of an electromagnetic circuit arrangement for aligning the light guides shown in FIGS. 1 and 2;

FIG. 4 is a side cross-sectional schematic view of one embodiment of an expanded beam coupling apparatus of the present invention;

FIG. 5 is a partial cross-sectional schematic view of a completed coupler coupling two fiber optic cables together;

FIG. 6 is a perspective block diagram of a multi-channel fiber optic cable termination constructed in accordance with the present invention;

FIG. 7 is a cross-sectional view of the assembled device shown in FIG. 6;

FIG. 8 is a cross-sectional and partially schematic view of another embodiment of the alignment apparatus and method of the present invention;

FIG. 9 is a schematic view of another embodiment of the alignment apparatus and method of the present invention;

fig. 10 is a schematic optical diagram of an optical path in another embodiment of a connector and a terminal device of the present invention;

FIG. 11 is a perspective view corresponding to the side view of FIG. 10;

FIG. 12 is a cross-sectional view of a preferred coupler of the present invention;

FIGS. 13 and 14 are cross-sectional views taken along lines 13-13 and 14-14, respectively, of FIG. 12;

FIGS. 15-17 illustrate a partial schematic cross-sectional view of the manufacture of the terminal shown in FIG. 12;

FIG. 18 is a partially schematic cross-sectional view of an electro-optic transducer arrangement constructed in accordance with the present invention;

FIG. 19 is a left side view of a component of the device of FIG. 18;

FIG. 20 is a schematic partial cross-sectional view of another embodiment of a transducer arrangement of the present invention; and

FIG. 21 is an enlarged cross-sectional view of another embodiment of the present invention; and

FIG. 22 is like FIG. 21 and schematically illustrates a view of another embodiment of the invention.

Detailed Description

Terminal device

Fig. 1 is a cross-sectional view of a fiber optic cable termination 20 constructed in accordance with the present invention.

The terminal 20 includes a standard ceramic ferrule 22 having a larger bore 21, the bore 21 being tapered at 23 to form a substantially smaller fiber conductor passage 32.

Conforming to the ferrule 22 is the end of a fiber optic cable 24 including a single mode optical fiber 30 extending through the passageway 32 and a coating 28 having a different index of refraction than the optical core 30 and finally an outer protective coating 26. Typical dimensions of the cable are: the outer diameter of the cable with the coating 26 is 250 micrometers; the cable diameter without coating 26 was 125 microns; and the optical fiber or cable core 30 has a diameter of 8 microns.

The diameter of the cable is small; particularly the cable core has a diameter of only 0.008 mm (about 0.0003 inch). It is therefore difficult to properly align the end of the cable core 30 in the terminal 20 coaxially with the cable core in another cable to be coupled to the cable 24 within 20 minutes.

Attached to the right end of the ferrule 22 is a reflector mounting structure 34. A reflector unit 40 is attached to the mounting structure 34. A soft plastic cushion pad 48 is fixed to the right surface of the reflector unit 40. It provides cushioning for the terminal from damage and covers and protects the central reflector of the terminal of the reflector unit 40.

The reflector mounting structure 34 has a central cavity 37 in which is disposed an annular member 38 of magnetically permeable material such as iron, iron-nickel alloy or the like, of similar size to the core memory elements such as have been used in core memories for many years.

The cavity 37 has an outlet 39. The light or cable core element 30 extends through the center of the annular member 38 to a point adjacent or near the left surface of the reflector unit 40.

The reflector element 40 is preferably a solid transparent glass or plastic body member having a metal (e.g., gold) coating or a dielectric coating on the left curved surface and the right concave central portion of the element at 42. The reflector unit thus has a first small reflector 42 of a size sufficient to intercept all or substantially all of the light emitted from the conductor 30. This small reflector 42 is flat or curved and is at an oblique angle to retroreflect light it receives to a larger reflective surface 44. Because of the angle of inclination of the reflector 42 and the curvature of the reflector 44, light from the core forms circular beam parallel (collimated) rays 46-47 extending parallel to the longitudinal axis of the sleeve to the right in figure 1.

Although the preferred embodiment of the present invention is described using single mode fibers, the present invention may also be used with multimode fiber cables.

Gold is just one example of a metal that can be used to coat the curved surface of a transparent block to form a reflector. Other metals such as silver, aluminum, etc. may also be used. If necessary, a dielectric material may be used instead of the metal.

The surface of the block not coated with the reflective material is preferably coated with an anti-reflective coating to prevent unwanted reflections. Alternatively or additionally, further reflection suppression is provided as shown in fig. 21 and as follows.

The particular reflector unit 40 shown in fig. 1 is a relegated-kerritin (Ritchey-Chretien) type optical unit, which is primarily depicted in fig. 10 and 11.

However, the preferred embodiment of the present invention uses a cassegrain type optical unit, which will be described in fig. 4 and below.

Cassegrain optical system

Fig. 4 is a schematic diagram showing two identical cassegrain reflector units 41a and 41b mated together face-to-face via flat transparent plates 64 and 66 to form the basic optical unit of one embodiment of the connector of the present invention. Light is emitted from the core 30 of the cable 24 and passes through the optical coupling structure to the core 33 of the second cable 31, thus providing a fiber optic cable connector. Certain parts of this structure are omitted from fig. 4 for clarity of illustration, including elements that mechanically secure the two halves of the coupler together.

The two reflector units 41a and 41b are identical to each other, so corresponding portions are given the same symbols.

Each cell includes a small convex reflector 45 and a large convex reflector 43.

The small reflector 45 is sized to intercept all or substantially all of the light 57 emanating from the cable core 30. The two reflectors 45 and 43 have a predetermined curvature such that the respective light rays are reflected from the first reflector 45 onto the second reflector 43 and then exit the unit 41a, e.g. along parallel lines 49, 51 and 53, thus collimating the light rays.

In a typical cassegrain reflector system, the large or "primary" reflector 43 is parabolic and the small reflector 45 is hyperbolic. However, the surfaces of the two reflectors may also have any other shape that produces the desired result.

Light from the core 30 of the cable 24 enters the reflector unit 41(a) via an aperture 30 in the main reflector 43 located on a rotational axis 77 of a paraboloid or other surface of revolution forming a reflector.

The collimated light is then received by the reflector 43 of the second reflector unit 41b and reflected back to the reflector 45 and transmitted through an aperture 33a in the reflector 43a located on axis 77 to be focused at the end of the second cable core 33. Thus, the light is transmitted to the second cable 31.

Advantageously, each cell 41a and 41b is made by a relatively simple method.

First, the body is molded by machining or with clear optical glass or plastic, with curved surfaces at the two reflector locations 43 and 45. The glass and plastic have refractive indices that closely match the refractive index of the cable core 30. The solid material of the two units 41a and 41b is indicated by the symbol 55 in fig. 4. The outer surfaces at 45 and 43 are then coated with a metal such as gold by a process such as vapor deposition or sputtering to form reflectors, and an anti-reflective coating is applied to the light transmissive output face. This approach can produce a small, robust and accurate integrated reflector unit at a reasonable cost.

Then, colorless plastic or glass plates 64 and 66 are attached to the flat surfaces of the reflector bodies 41a and 41b, respectively, with an adhesive such as an index-matched transparent epoxy resin. The purpose is to make the mating surface at 68 very flat, thus virtually eliminating the possibility of the two units 41a and 41b being angularly skewed relative to each other.

Alternatively, the two terminals may be aligned using optical methods described elsewhere herein, and plates 64 and 66 may be eliminated.

One modification of the above is to form holes in the blocks 41a and 41b along the optical axis 77, into which the ends of the light guide 30 are inserted. This enables the end position of the light guide to be adjusted closer to the reflector 45. If such a modification is used, the aperture should be sufficient to allow the conductor 30 to move for alignment.

Coupler

Fig. 5 is a cross-sectional view of a coupler 59 similar to that shown schematically in fig. 4. The two reflector units 41a and 41b are fixed to the mounting blocks 71 and 73, respectively. The mounting blocks 71 and 73 are preferably molded from an opaque plastic or glass material. The block 71 has a frusto-conical cable inlet 70 and the block 73 has a cable inlet 70 identical to the block 71. The frusto-conical opening facilitates entry of the cable into the connector.

The cable 24 includes a protective coating 26, a covering 28, and a core 30. The cable 31 includes an outer protective coating 61, a covering 35, and a cable core 33.

Each block 71 and 73 has a circumferential groove 72 adapted to receive a sharp inwardly extending edge 74 of a clip 75, said clip 75 securing the two halves of the coupler 59 together. The clip 75 is one of many different well-known means for securing the two halves of a fiber optic coupler together. Any other means may be used in accordance with the present invention as the clip or other securing structure does not form part of the invention as claimed herein.

It is preferred to replace plates 64 and 66 with buffer 48 and align the cable cores using the alignment method described below.

It should also be understood that the cable termination 20 shown in fig. 1 is typically used as part of a cable coupler that is comprised of another termination 20 connected to another cable and a clip or other securing structure that secures the termination structures together.

Because the coupler disperses the light beam passing through the tiny light guides 30 substantially, the coupler is much less sensitive to dirt and lateral (e.g., perpendicular or at right angles to FIG. 4) alignment errors. By collimating the light precisely, the sensitivity to distance errors separating the two coupler halves is almost eliminated. In addition, the serious disadvantage of using a lens or other refractive means to disperse and collimate the light is largely eliminated.

Coaxial alignment device and method

Fig. 2, 3 and 9 illustrate one embodiment of the alignment apparatus and method of the present invention.

Fig. 3 is a schematic diagram showing a rotating magnetic field forming and controlling device 58 for generating and controlling a rotating magnetic field around the ring-shaped magnetic element within the terminal 20.

As shown in fig. 1, there is sufficient space between the element 38 and its cavity 37 wall so that it can essentially make side-to-side movement in any radial direction to align the light guide 30 with an object, such as another fiber optic conductor in another cable.

The rotating field forming device is a structure conventionally used to form a rotating magnetic field for use in an electric motor, with some exceptions. Four pole pieces EM1, EM2, EM3 and EM4 are placed at equal angular intervals around the magnetic member 38. Basically, each pole piece is positioned at 90 ° to its neighbors. A cosine signal generator 60 supplies a cosine wave voltage to the windings as shown via diodes D1 and D3 and resistors R1 and R3.

A sine wave signal generator 62 is provided and supplies a sine wave voltage to the windings as shown via diodes D2 and D4 and resistors R2 and R4. This creates a magnetic field that rotates about a central point.

The four resistors R1, R2, R3 and R4 may be respectively changed so that the amplitude of the signal supplied to each pole piece can be changed to move the effective center point or the neutral magnetic flux point of the rotating magnetic field.

Figure 2 is a perspective view showing the light guide or cable core 30 extending through the center of the magnetic element 38. The cable 24 is clamped in a clamping device that includes a V-groove support 98 (fig. 9) and a clamp 102 to secure the cable 24 in the given position. The reference numeral 56 in fig. 2 schematically represents the position where the cable 24 is fixed. The pole pieces of the rotating magnetic field device 58 shown in fig. 3 are schematically indicated at 110 in fig. 9. They surround the right end of the terminal 20 and the magnetic element 38 is centrally located as shown in fig. 3.

The cable and light guide 30 can be moved along the Z-axis, i.e., in the direction indicated by arrow 54, by standard micrometer adjustment mechanisms provided in existing alignment devices. The location of the Z axis is not critical. However, the positioning along the X and Y axes as shown in FIG. 2 is important.

The circular arrow 52 in fig. 2 indicates the direction in which the magnetic field rotates about the element 38. The line 50 in the figure illustrates the force at a particular instant when the magnetic field rotates.

Referring again to fig. 9, the control unit 124 contains the circuitry shown in fig. 3 and supplies signals to the windings 110. The control unit 124 has four round handles 125, and each round handle 125 is used to control one of four variable resistors in the circuit. In this way the balance of the magnetic field can be changed to move the ring 38 to almost any position within the cavity 37 in the X-Y plane as shown in figure 2.

As shown in fig. 9, a second V-groove support block 100 supports a second terminal 20 for terminating a second cable 25. The cable 25 is fixed in position by a clamp 104.

Referring again to fig. 1, the reflector base unit 34 has a hole 36, the hole 36 allowing uncured epoxy to be injected into the chamber 37 to completely surround the magnetic toroid 38 and the end of the fiber optic conductor. For this purpose, a hypodermic needle type applicator may be used.

Referring again to fig. 9, an optical signal generator 120 is provided for transmitting a test signal to the terminal 20 via the cable 24. The left end of the terminal 20a supported on the block is adjacent to the right end of the terminal 20 in the drawing. However, the terminals may be separated by a significant distance without any significant error due to the collimated light transmission therebetween. The signals generated by the transmission through the two cables are transmitted to a receiver 122 for converting the signals into representative electrical signals representing the magnitude of the transmitted signals.

In accordance with one aspect of the present invention, the viscous epoxy injected into the terminal 20 may be cured by external radiant energy. In this case, the epoxy resin is preferably a photocurable epoxy resin (e.g., manufactured by Loctite Company and others). This epoxy is selected to have an index of refraction that closely matches the glass or plastic mirror body and the cable core 30.

Referring again to fig. 9, a light source 118 of an appropriate wavelength is provided to illuminate the fiber on an area near the right end of the terminal 20, or on the exit end of the terminal. The transparent housing and/or the optical system itself transmits light to the epoxy.

The rotating magnetic field forming means in unit 124 are energized as are signal generator 120 and receiver 122. With the round handle 125 adjusted for resistors R1-R4, the core 30 of cable 24 may be properly aligned with the core of cable 25 as shown in FIG. 9. The perfect alignment may be detected when the signal received by the receiver has the position of the maximum. When this point is reached, further adjustment is stopped and light from the light source 118 is used to cure the epoxy and fix the position of the cable core. Then, the alignment is completed.

The photocurable epoxy resin preferably has a low tack during the start of the alignment procedure and thickens (tack increases) during the procedure, typically taking several seconds to cure properly. Advantageously, it is likely that a large adjustment movement is required early in the curing process where the viscosity is low, and fine-tuning is performed later. Thus, the curing and alignment of the epoxy can be performed simultaneously to speed up the alignment process.

Preferably, the alignment procedure can be automated using a closed loop control system and a programmed computer that uses an algorithm to automatically adjust the balance of the magnetic field to align the terminals so that the signal received by the receiver is at a maximum.

The cores of the cables 25 in the right-hand end of figure 9 are preferably already aligned before the alignment procedure described above is initiated. Thus, the cable 25 and its termination may be used as a "standard" to provide alignment of the cores of a variety of different terminations (like termination 20). Alternatively, the cable 25 may be a piece of actual cable that is required to create a coupling.

Although the use of a controllable rotating magnetic field has been described as the preferred means of adjusting the position of the cable core, other variable magnetic field generating means may be used provided they generate variable magnetic fields in at least two orthogonal directions to enable the cable core to be positioned at various different positions in the X-Y plane.

In another embodiment of the alignment apparatus and method of the present invention, instead of using a magnetically permeable element surrounding the fiber optic cable core, one or more magnetically permeable bands may be formed around the body of the reflector unit 40. The unit 40 fits loosely within the ferrule so it can move, and the rotating magnetic field is used to move the reflector unit relative to the stationary fiber optic cable core to achieve alignment. The reflector unit 40 and the cable core 30 are then secured in alignment with each other by curing the liquid epoxy surrounding the ends of the reflector unit 40 and the cable core 30.

Visual alignment

FIG. 22 shows a visual alignment system that may be used in conjunction with or in place of the alignment system and method described above.

In the system shown in fig. 22, a viewing device 280 is used to view through the outer surface 254 of the reflector block 250 to form an image of the source point, the cable end 270 and the flat 256 with the cable end or the input/output port with a transducer.

The viewing device 280 may be a microscope having its own light source to transmit light along the path shown by the dashed line 286.

The viewing device is preferably a video camera 282 having a micro zoom lens 284 which forms a video signal which forms an image of the reflector block 256 and the flat portion of the cable end 270 and passes those signals to a digital controller which processes the signals and, after processing, passes the signals to a video display monitor 292. The processing may include signal enhancement and other procedures to improve the image depending on the desired use.

Monitor 292 has a screen 298 that displays the image of the target circle 257 formed on the flat portion at 256, as well as the cross-wires 306 and the image 271 located on the end of the fiber optic conductor 270. The target circle 257 may be etched or otherwise formed on the surface of the flat portion 256 at the time of manufacture.

A control unit 296 is provided for controlling the four orthogonal magnetic fields applied to the magnetic element 172 by four orthogonally positioned coils, two of which are shown as 302 and 304 in fig. 22. The signals to the coils are automatically controlled by a manual control such as a joystick 300 or preferably by a computer program with a microcomputer in unit 296 to align the fiber optic conductor ends with the targets 257, 306.

Because the viewing angle of the viewing device 280 is off axis, the target 257 and the fiber-end image 271 may be slightly elliptical, i.e., their height may be greater than their width. This is considered acceptable and does not prevent accurate alignment. Additionally, the angle may provide a depth perception sufficient to enable detection of the axial position of the end of the conductor 270 relative to the flat 256, such that the position can be adjusted by a micropositioner to bring the end of the conductor into abutment with the flat 256.

Also shown in fig. 22 is a curing radiation source 288 which transmits curing radiation along a path indicated by dashed line 290 to the flat 256 in the end region of the surrounding fiber conductor 270 to cure the liquid epoxy surrounding the conductor ends, fixing its position after alignment is completed.

The curing source 288 preferably generates radiation at a wavelength different from the wavelength of the signal transmitted through the cable conductor. For example, most such signals have wavelengths in the infrared range, while radiation from source 288 is preferably in the ultraviolet or visible blue region of the electromagnetic spectrum. The advantages are that: the signal transmitted by the fiber optic conductor 270 does not interfere with the proper curing of the epoxy. This facilitates the attachment of the terminal to an end of a cable in the field without the need to cut off the signal source. This makes field alignment faster, easier and cheaper.

Typically, the light incorporated into or attached to the viewing device 280 emits light at a different wavelength than the source 288 and the signal transmitted through the fiber optic cable. Typically, this light is visible light. However, the wavelength of light from the light viewing device 280 may be selected to cure the epoxy, so the alignment and curing steps may be performed simultaneously, and the separate source 288 may be eliminated.

The alignment apparatus and method shown in fig. 22 has significant advantages, particularly for alignment performed in the field. Because the alignment method does not depend on the transmission of signals over the fiber optic cable, any signals that may pass through the cable do not need to be cut off, and receivers that match those signals do not need to be provided. Furthermore, a second terminal and cable to the receiver are not required. The visual alignment apparatus may be compact and portable to facilitate field use.

In a factory or laboratory, the visual alignment method may be used as an aid to or in place of the alignment apparatus shown in fig. 8, as long as time or cost can be saved.

Although the foregoing alignment devices and methods have been described primarily for use with fiber optic cables, it should be understood that they are well suited for aligning a reflector unit 250 with a transducer or similar device as shown in fig. 18.

Splice joint

Fig. 8 illustrates the use of the present invention to splice fiber optic cables together.

Unlike those easy-to-disengage couplers described above, the splice is intended to create a permanent connection between two cables. Thus, it is less prone to problems such as dust that plague releasable connectors, and beam expanders and collimators are often not required.

Fig. 8 illustrates one method for splicing together two cables 88 and 90. First, a short piece of the cladding and outer coating is removed from each cable end, as shown at 92 and 94, and the cable core ends are cleaved using conventional cleaving apparatus and methods.

A transparent plastic or glass sleeve 105 is provided. It has an access aperture 108. The inner diameter of the sleeve 105 is substantially larger than the outer diameter of the cables 88 and 90 to provide room for the ends of one or both cables to move laterally to align the ends together. The cable 88 is held stationary by a V-block 98 and clamping device 102 and the other cable 90 is held by a similar block 100 and clamping device 104. The ends 92 and 94 are inserted into the sleeve 105 with the ends close to each other but not touching each other.

In one embodiment of the splicing method, a magnetically permeable sleeve 106 surrounds one end of the sleeve 105 and is attached to the outside of the sleeve 105.

In effecting articulation, a rotating magnetic field generator 110 is positioned around the sheath 106 as shown in FIG. 8, and the controller of FIG. 9 and the signal generator 120 and receiver 122 of this figure are used to position the cable cores 92 and 94 in alignment with each other as described above.

The mechanical device for realizing the above functions is as follows: as the sleeve 106 is moved laterally by the magnetic field, the sleeve 106 supports the cable 90 causing it to bend and move the end 94.

Before alignment, a light curable epoxy is injected through the hole 108 as shown at 114 to fill the interior of the jacket 105 around the ends of the two cables. When or before alignment has been achieved, a light source, represented by arrow 112, is energized to irradiate the epoxy and cure it, if necessary. At the end of the method, the cable ends have been firmly enveloped after alignment to complete the splice.

Fig. 8 illustrates a second method for implementing an alignment method during cleaving. Instead of using a sleeve 106, the magnetic ring 38 shown in fig. 1 and 2 is placed around the end of one of the cables. Then, in the manner described above, a rotating magnetic field source 110 is positioned around element 38 and operated until the cables are aligned.

In this method, it is necessary to mechanically locate the other cable end approximately to the center of the jacket before the alignment process and epoxy curing step are performed.

In either case, the cable can be quickly, easily and accurately aligned in the field.

rEsQi-Krigin optical system

Fig. 10 and 11 are enlarged schematic views of the optical path of a typical resizer-gratin system similar to that shown in fig. 1. The system is characterized in that: the light source shown in fig. 10 is not located on an axis with a large mirror surface. Thus, there is no insertion loss due to the hole in the large mirror required in the Cassegrain system described above. Thus, the system of resique-kristin has its advantages in itself and can be used in many situations. However, the beam spread using such a system is smaller than in the case of the cassegrain system, and the cassegrain system can be considered somewhat easier to manufacture.

As shown in fig. 10 and 11, light rays 128 exiting the output of the cable 24 reflect off a slightly curved reflector 126, which reflector 126 reflects the rays along a line 134 to a slightly curved large reflector 132. The curvature of the surface is hyperbolic or other curved shape and is calculated as shown in fig. 10 to produce parallel reflected rays 136 above a vertical region 138.

As shown in fig. 11, the area occupied by ray 136 is roughly circular, as is reflector area 132.

In addition, the optical system shown in fig. 10 and 11 can be made by molding a block of optical glass or plastic and metal-coating the surfaces 126 and 132 by vapor deposition or sputtering or the like to produce the reflecting surfaces. Therefore, the optical system is also cheaper than the existing beam expanding type terminal.

Alternative optical system

Optical systems other than cassegrain and reox-criniton may be used. One example is the griigoritian (Gregorian) system, which is similar to a cassegrain type, but differs in that: the griighback system uses a first reflective surface of a different shape. Other known variations may also be used.

Multi-channel connector

Fig. 6 is a perspective view of one terminal of a multi-channel connector. A number of optical fibre cables (12 in this example) 20 are inserted into V-grooves 86 in a cogwheel-shaped support 83 having a central through-hole 84. A clear plastic or glass sleeve 78 fits around the exterior of the terminals 20 and holds them securely in place within the slots 86. A colorless plate 80 of fused silica or sapphire forms a window secured to the end of the housing 78. This forms a flat surface against which the connector terminal 20 fits.

A central metal pin 82 having a notch 85 at one end fits into the hole 84 and the hole through the center of the plate 80.

The pin 82 serves to align the terminal with a notch-like tip 85 provided to align the two terminals at the proper angle to each other.

The individual cable terminations 20 are preferably potted in place after assembly as shown in fig. 7.

Preferred coupler

Fig. 12 shows a preferred coupler 150 coupling two preferred terminals 152 together. In basic principle terms, the coupler 150 and the termination 152 are substantially the same as shown in fig. 5. However, the curvature of the reflector is closer to what actually creates the existing curvature. Also, there are various improvements that are advantageous for manufacturing, durability, and the like.

As with the coupler of fig. 5, the two fiber optic cables 24 and 31 are coupled together.

Each terminal 152 includes a ferrule 154 (see fig. 15). The ferrule 154 includes a reflector unit cavity 156 having a ledge 158, the ledge 158 forming a base for a reflector unit 178.

Fitted within a magnetically permeable alignment element 172 is a cavity 160 of slightly smaller diameter. Another compartment 162 of narrower diameter connects the compartment 160 with a small passageway 164 of slightly larger diameter than the cable section 28 fitted through it.

The collar has a flange 166, a smaller diameter section 168 and an elongated sleeve 170 which terminates the collar structure.

Referring again to fig. 12, the magnetic element 172 is generally annular in shape, as is the element 38 shown in fig. 1. The right end 174 is smaller in diameter than the left end 175. Also, it has a larger frusto-conical inlet 176 for guiding the cable through its central bore. In general, the maximum diameter of the element 172 at the left end is only slightly smaller than the chamber 160 into which it fits. This will have the effect of approximately centering the element 172 into the cavity 160, while the smaller right end has more room for movement to align the core of the cable, if necessary.

The large tapered entrance ensures that the cable end passes through the central bore of the member 172.

The reflector units 178 are substantially identical to the individual reflector units 41a or 41b shown in fig. 5, except that the curvature of the large reflector is much smaller than that shown in fig. 5.

Further, as shown in fig. 13, the reflective coating 180 for the large reflector does not largely cover the outside of the reflector. Instead, a central circular area 182 of significant size remains uncoated. The region 182 is also flat to minimize the spacing between the cable end and the reflector unit as the cable end is moved to achieve alignment and to prevent damage to the reflective coating 180.

The diameter of the uncoated region 182 is about the same as the diameter of the small reflector. Thus, the loss caused only by the uncoated area 182 is inherent to the Cassegrain-type design.

The bumper 48 is preferably permanently attached (e.g., by epoxy) to the back of the small reflector within each reflector unit 178. When the two terminals 152 are connected end to each other as shown in fig. 12, the buffer 48 is the leading contact point between the two terminals. They are preferably made of a relatively flexible plastic to minimize the impact transmitted through the reflector body.

The coupler 150 includes a cylindrical body 184 cut at 186, 187, etc. to form a central section having an inner dimension closely matching the outer diameter "D" of the front portion of the ferrule 154 (see fig. 15) so that the two terminals remain precisely aligned with each other.

Four spring arms or fingers 186 are formed at each end of the coupler 150 and terminate in hook portions.

When the terminals 152 are inserted into the ends of the coupler 150 and pushed together, the spring arms ride over the flange 166 and snap down so that the hook portions engage the outer surface of the flange to hold the two terminals together stably and securely.

The material of coupler 150 may be thermoplastic, metal, or other material suitable for the particular application and environment in which the coupler is used.

The configuration of the coupler 150 is but one example of the many different forms that the mechanical structure of the coupler may take.

Preferred method of manufacture

Fig. 15-17 illustrate a preferred method of manufacturing a terminal 152.

Referring to fig. 15, first, the alignment member 172 is inserted into the cavity 160. The metal walls at the terminal end around cavity 156 are then heated to a moderate temperature above room temperature as shown at 188 to moderately enlarge the chamber size. The reflector unit 48 is then inserted into the cavity 156 and the assembled terminals are cooled. This provides a shrink fit to securely mount the reflector unit 178 within the ferrule.

Referring now to fig. 16, where the ferrule 154 is in the opposite position to that shown in fig. 15, liquid epoxy is injected into the cavity 160 containing the alignment member 172, and the chamber is filled with epoxy to the opposite plane shown at 192, just covering the alignment member 172 completely. The liquid preferably has a low viscosity like water and is injected in a pre-measured amount through a thin tube 190, which thin tube 190 is temporarily inserted into the ferrule and then removed during the filling period.

Referring now to fig. 17, the stripped and cleaved cable end is then inserted into the ferrule until the cable end is very close to the flat area 182 on the reflector unit 178. A rotating magnetic field is then applied around the element 172, as shown at 196, and as described more fully above, the scattered white light shines in the cable to send a signal 198 to a receiver and device to determine where the signal has a maximum, all as described above. Light is fed into the cell via the reflector unit 178 as shown at 194.

The light applied at 194 serves a dual purpose. It irradiates the photo-curable epoxy located in cavity 160 and cures it just as the cable reaches the proper alignment and also generates signal 198 for alignment. This procedure takes only a few seconds to complete.

The manufacturing method is simple, fast and cheap and results in a superior coupling and termination.

Converter device

Fig. 18 is a partial cross-sectional schematic view of a transducer apparatus 200 constructed in accordance with the present invention.

The apparatus 200 includes a support structure 202 having a flat base 204 and a platform 206 supporting an electro-optic transducer 208.

The switch 208 has an input/output port 210 that is aligned with a dual reflector optical system 178, the dual reflector optical system 178 being identical to the unit 178 shown in FIGS. 12-17 and described above.

If the converter 208 is a light source, the dual reflector system 178 disperses the light beam to greatly magnify the light beam emitted by the converter and emits it as a collimated beam as shown at 214 in FIG. 18.

If the transducer 208 is a detector, the dual reflector unit 178 receives the beams 214 and concentrates or focuses them at the input/output port 210. By expanding and collimating the beam, the beam is ready to be easily coupled to a coupler for a fiber optic cable or another device. The divergence of the beam makes the optical system less susceptible to dust and other error-causing debris and greatly reduces the sensitivity of the device to coupling positioning errors.

Alignment of the transducer 208 and reflector system 178 is accomplished using a conventional micropositioner 218, in accordance with one embodiment of the present invention. The micropositioner 218 is capable of vertical adjustment along the Z-axis and horizontal adjustment of the position of the transducer 208 along the X and Y-axes (see fig. 18 and 19) to align the transducer with the cell 178.

Alternatively, an electromagnetic position adjustment system, as described below, may be used to position the reflector unit 178 relative to a fixed transducer unit 208, thus avoiding the use of a micropositioner.

Converter type

The diverter device of the present invention is capable of cooperating with almost any type of small light source or detector.

Useful light sources include light emitting diodes ("LEDs"); laser diodes, vertical surface emitting lasers ("VCSELs"); a bar-shaped laser device; and other semiconductor light emitting devices.

Some converters, such as LEDs, produce diffuse output light, while some have lenses that produce narrow beams of light.

Also, laser devices of the type described above produce beams of various shapes, typically narrow beam widths.

Basically, any device that can be used as a fiber optic converter or receiver is generally a converter with which the present invention can be advantageously used.

If desired, a hermetically sealed transducer unit may be made by forming a hermetically sealed housing around the components (after the micro-positioner 218 is removed) as shown at 220. Of course, when alignment has been achieved, the position of the transducer 208 is fixed to maintain alignment during use of the device 200. This may be accomplished by curing the epoxy or other known means.

Alternatively, a hermetic seal may be used for the interface between the input/output port 210 and the reflector unit 178. To this end, glass frit index matched to the reflector unit 178 may be melted around the interface between the input/output port 210 and the reflector unit.

Fig. 20 is a partial cross-sectional schematic view of another embodiment 222 of a transducer arrangement of the present invention. This embodiment is shown in use as a structure having internal walls such as wall 226, a glass exit window 230 and a fiber optic cable 226, thereby forming an optical transmission structure for transmitting light from the converter 208 in the case of a light emitter or to the unit 208 in the case of a detector.

This embodiment of the invention includes a first ferrule 224, which first ferrule 224 is similar in many respects to the ferrule shown in fig. 12-17, except that: there is no reflector element 178, but only a round pellet 172 of magnetically permeable material surrounds the end of the fiber optic conductor 28. With this arrangement, the fiber optic conductor 28 is aligned with the input/output port 210 of the transducer 208.

An electromagnetic field, preferably helical, is supplied from the exterior of ferrule 224 to properly align conductor 28 with the outlet in the manner described above.

The pellets and conductor are held in place substantially in alignment by an irradiated curable epoxy used to hold the pellets 172 in place in the chamber as described above. Although not shown in fig. 20, a structure is provided for supporting the ferrule 224 relative to the bottom 234 of the transducer assembly 208 to maintain the end of the fiber optic cable in alignment with the port 210.

Preferably, the body of the collar 224 may extend as shown by dashed line 336 and be internally threaded to fit over the external threads of the port extension 210. Similar mounting arrangements may be provided by those skilled in the art within the scope of the present invention.

The fiber optic cable 26 extends through a bushing 232 positioned within a bore in the wall 226 and into a second terminal 228, the second terminal 228 preferably being substantially identical to one of the terminals shown in fig. 12-17. I.e. it has a ferrite bead 172 and a reflector element 178. The ferrite bead 172 is used in the manner described above to align the right end of the cable core or conductor 28 with the reflector block 178.

Light is emitted or received through the window 230 to communicate with the converter 208.

Also, with the embodiment shown in fig. 18 and 19, a hermetically sealed enclosure 236 may be provided to form a hermetically sealed converter unit with a wide output beam or input receiving area to achieve the advantages described above.

Alternative alignment structures and methods

It should be appreciated that it is not necessary to move only one fiber optic conductor when aligning such a conductor with a reflector unit or other optical device or system. All that is required is the actuation of one of the two structures relative to the other. Thus, as mentioned above, it is within the scope of the invention to provide a magnetically permeable ring or similar element around the body of the reflector unit 178 and position it in a chamber slightly larger than its outer diameter, and use electromagnetic field alignment mechanisms to move the reflector unit relative to the fiber optic conductor or other object (e.g., for an input/output port of the transducer) to produce the desired proper alignment.

Thus, in this alternative embodiment, the device of FIG. 18 does not use micropositioners such as 218, but rather uses this alternative alignment structure and method, where the inner diameter of the support structure 212 for the reflector cell 178 is slightly larger, and a ferromagnetic material would surround the cell 178. The reflector unit then tends to be aligned perpendicular to the plane of least reluctance of the surrounding magnetic field.

Reflection suppression

One of the problems with any joint between the ends of a fiber optic cable is signal back reflection at the air-fiber interface. Techniques for suppressing this reflection include: rounding the end of the cable; filling the air gap between the ends of the fibers with a refractive index matching gel; cutting the fiber ends at an angle ("angle polishing" technique); butting the tail ends of the cable cores together; and coatings using antireflection.

It is believed that the use of only an anti-reflective coating on the surface of the reflector unit 178 does not provide sufficient reflection attenuation for most fiber optic cable communication systems. Therefore, another suppression device and method are preferably used.

The suppression means used are shown in fig. 21.

Fig. 21 is an enlarged cross-sectional view of a reflector block 250 made of light-transmissive glass or plastic and having a curved first surface 252, an opposing second surface 254, and a reflective coating 260 on the surface 252, but excluding a flat area 256 forming an inlet/outlet.

A small convex reflector 258 is opposite the reflector 260. A buffer 48 is provided as described above. The reflector block 250 is constructed the same as block 178 except that: the inlet/outlet surface 254 is slightly convex rather than flat, and preferably the surface 254 is parabolic.

The curvature of the surface 254 is such that the reflected beams, such as beams 266 and 268, are at an angle a relative to the beams leaving the reflector block. When having been transmitted through reflectors 260 and 258, they do not intersect fiber optic cable core 270 but pass outside it, as indicated by arrow 264. This results in a very effective reflection suppression.

The exiting beams are slightly refracted as they exit surface 254 and this effect will be taken into account when designing the reflector volume so that the output beams 262 are parallel to each other.

Although it is believed that the suppression structure and method will produce sufficient suppression for most applications, surface 254 may also be coated with an anti-reflective coating to increase reflection suppression, if desired.

It should be understood that the above-described structures and methods may be used to align the reflector unit 250 with any light source or receiver, as well as with a fiber optic light guide for use with converters and cables.

Definition of terms

Certain terms used above in the specification have a defining role for this patent application.

The term "light" as used in this patent application includes electromagnetic radiation other than visible light. It includes, inter alia, infrared and ultraviolet radiation and other electromagnetic radiation of the electromagnetic spectrum close to the above-mentioned radiation spectrum.

The term "fiber optic cable" includes single mode and multimode cables, although the examples are single mode cables. It also includes "hollow" fiber optic cables in which light is conducted through air as a central conductor.

The term "on-site" is used to refer to work performed outside of a laboratory, factory, or other such facility. The procedures described herein that may be performed "on-site" are intended to include procedures that can be performed at a mobile service vehicle, a customer location, and the like. In an emergency situation, the term may also include maintenance performed in the open air.

"radiation curable" materials that can be used in the present invention include epoxy resins and similar materials that can be cured by exposure to ultraviolet, infrared, gamma or other radiation.

"Reflector elements" include not only the particular Rake-Critide and Cassegrain systems, but also similar reflective systems that have been found to be useful in telescopes or similar optical devices.

"magnetic element" means a magnetically permeable element.

"converter" is used to describe any device that converts an electrical signal into light, infrared or other radiation in the invisible region of the electromagnetic spectrum or converts an electromagnetic radiation signal, such as light, into an electrical signal.

The foregoing description of the invention is intended to be illustrative rather than limiting. Various changes or modifications to the above-described embodiments may be made by those skilled in the art. This may be done without departing from the spirit and scope of the invention.

Claims (5)

1. A fiber optic cable termination device comprising: a housing for supporting and holding an optical fiber conductor having a distal end; a first reflector secured to said housing and positioned to receive and reflect light emitted from said distal end; a second reflector secured to said housing and positioned to receive light reflected by said first reflector and project said light in the form of a collimated beam having a diameter substantially greater than the diameter of light emitted from said end; a magnetically permeable element positioned within the housing and responsive to an external magnetic field to move the tip laterally.

2. The fiber optic cable termination device of claim 1, wherein the first reflector and the end of the fiber optic conductor are located outside of an optical path of light reflected by the second reflector, the end and the second reflector being substantially aligned with the second reflector positioned between the end and the first reflector.

3. A fiber optic cable connector comprising: an elongated tubular housing into the opposite ends of which the ends of the two fiber optic cables extend and which ends are adjacent to each other; an element made of magnetically permeable material positioned within said housing and coupled to at least one of said ends for moving said at least one end in response to an external magnetic field, said housing being receptive to curing radiation, and said fiber optic cable ends being embedded in a mass of radiation curable epoxy.

4. A method for connecting two fiber optic cables together and coaxially aligning the ends of two fiber optic conductors in the cables with one another, the method comprising: a) inserting said ends into a housing having a body of magnetically permeable material attached to at least one of said ends; b) moving the body of magnetically permeable material laterally by magnetic force until the ends are aligned with one another; c) with the conductor ends aligned with each other, the ends are secured together by radiation curing plastic.

5. A method of manufacturing a fiber optic cable termination device, the method comprising the steps of: a) providing a ferrule having a first chamber for a lens system and a cable receiving tube leading to said first chamber via a second chamber; b) positioning a magnetically permeable element within said second chamber, said magnetically permeable element having a central bore for receiving an end of said cable; c) installing the lens system within the first chamber; d) introducing a hardenable liquid radiation curable plastic into the second chamber; e) inserting a cable end into the magnetically permeable element through the central bore; f) applying a magnetic force to the magnetically permeable element to align the cable end with the lens system; and g) hardening the liquid radiation-curable plastic to fix the position of the cable end.