GB1601277A

GB1601277A - Optical fibre connector

Info

Publication number: GB1601277A
Application number: GB18532/78A
Authority: GB
Original assignee: Hughes Aircraft Co
Current assignee: Raytheon Co
Priority date: 1977-06-10
Filing date: 1978-05-09
Publication date: 1981-10-28
Also published as: FR2394103A1; CA1096213A; JPS57157911U; DE2824507C2; FR2394103B1; JPS6037527Y2; DE2824507A1; JPS545748A

Description

(54) OPTICAL FIBRE CONNECTOR (71) We, HUGHES AIRCRAFT COM PANY, a corporation organized and existing under the laws of the State of Delaware, United States of America, of Centinela and Teale Street, Culver City, State of California, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to a connector for coupling single and multiple strand optical fibre conductors.

A fundamental problem in the interconnection of optical fibre conductors is the alignment of the fibres of the two conductors.

A further problem is the ability to maintain such alignment under repeated engagement and disengagement cycles. It is desirable that this precise coupling be accomplished without the use of index matching materials, since they are prone to contamination and could degrade coupling efficiency after several engagement and separation cycles. Typically, such conductors have a diameter of approximately 0.005 inches (0.127 mm). Because even minute misalignment between mating optical fibre conductors results in significant transmission loss, it is imperative that they be precisely aligned. With very small diameter conductors, it is apparent that the alignment task for single strand fibres is formidable. Alignment between multiple strand fibres is even more difficult.

Present optical fibre interconnects are known, and their losses have been advertised to be 0.5 db to 3.5 db. Such a variation in loss means that it is not possible to obtain effectively repeatable alignment.

It is further desirable to prevent the ends of the optical fibre conductors to contact and, therefore, to be scratched. Such scratching or other damage causes the light being transmitted to be diffused with consequential loss in light transmission.

In addition to these and other considerations, it is also desirable that the connector bodies receiving the optical fibre conductors be capable of receiving, at the same time, conventional electrical conductors and contacts so that mixes of the two electromagnetic signal carrying means can be realized. As a corollary, specialization in parts and stock and manufacturing equipment can be avoided if the same connector blocks and other termination hardware are used for coupling of both electrical as well as optical conductors.

With a view to meeting these desiderata, the present invention provides a connector, coupling optical fibre conductors together at their termini, wherein: said optical fibre conductors at their termini have respective enlargements whose peripheries are of a predetermined external dimension; a sleeve formed of resilient material, is formed with a longitudinal split, with the interior dimension of the sleeve being slightly smaller than the external dimension of said enlargement peripheries, and whose interior is mated to the said enlargements of said optical fibre termini, resiliently contacting and thereby commonly aligning both said conductors; and a spacer is loosely supported by and within said sleeve and between said enlargements to space said termini of said optical fibre conductors from mutual physical contact.

In a preferred embodiment of the invention the split sleeve accepts alignment bushings attached to each end of the optical fibre connectors, the bushings defining said enlargements at the fibre termini. The optical fibres are received in holes in the bushings and the hopes are precisely concentric with the bushing peripheries. The bushings as well as the sleeve are precisely dimensioned, for example in circular or polygonal crosssection (corresponding identically in shape to that of the holes in the bushings), to provide for the greatest possible concentricity and actual alignment between the optical fibres coupled. To mate and align the bushings, they are slid into the split sleeve which acts as a spring. Thus, alignment of the bushings automatically and precisely aligns the optical fibres and permits coupling and uncoupling cycles. To prevent contact of the conductors at the interface between the bushings, the spacer, typically a shim, is positioned in the sleeve and comes into contact with only the bushings. The optical fibre conductors are received in contacts which are configured to permit their insertion into conventional electrical connector bodies. Thus, mixes of optical and electrical conductors and couplings are obtainable in the same conductor block.

In order that the invention may be more fully understood and readily carried into effect exemplary embodiments thereof will now be described with reference to the accompanying drawings wherein: Figs. la and lb are views in cross-section, of a pair of connector bodies with single strand optical fibre conductors and contact bodies therein coupled together, with one strand having a larger diameter than the other, Fig. 2 is a perspective view of one of the contact bodies of Fig. 1 with its optical fibre conductor terminated therein; Fig. 3 is a perspective view of the split tube or sleeve shown in Fig. 1 used to obtain precise alignment between the coupled optical fibre conductors; Fig. 4 is a view of the shim used to prevent contact between the coupling optical fibre conductors of Fig. 1; Fig. 5 is an end view of a second embodiment of the present invention illustrating a hexagonally shaped bushing used to terminate a conductor having multiple strands of optical fibres; Fig. 6 depicts a pair of bushings, as shown in Fig. 5, coupling multiple stranded optical fibre conductors together with a hexagonally shaped split sleeve properly aligning the fibre termini; and Fig. 7 depicts the combination where both electrical wires and optical fibres are positioned in a common connector body.

Referring to Figs. 1--4, a pair of contacts 10 and 12 are positioned within their respective connector bodies 14 and 16 in any conventional manner, such as by retaining clips 18 and 20. These retaining slips reside within recesses 22 and 24 of their respective contacts and are adapted to engage annular portions 26 and 28 of their connector bodies.

Each contact 10 and 12 includes a contact body 30 and 32 with a pressure-sensitive wire seal, such as seal 34, attached at the rearward end 36 of contact body 30. Such a pressuresensitive wire seal 34 is described in United States Patent No. 3,792,416, which also utilizes similar retaining clips 18. At its opposite or forward end 38, contact body 30 carries an alignment bushing 40, which is secured to end 38 in any convenient manner.

Bushing 40 is provided with a precisely formed hole 41 for receiving the terminus of an optical fibre 42. The diameter of hole 41 is made as close as possible to that of fibre 42.

Abutting against alignment bushing 40 is a spring spacer 43, which is provided with an upstanding spring abutment end 44. Spaced from upstanding abutment end 44 is a second spacer ring 46 which abuts against a surface 48 of contact body 30. Positioned between spacers 43 and 46 are a plurality of spring washers 50, these spring washers will become evident hereinafter.

Contact body 30 is further provided with a through bore 52 extending from its rearward end 36 to its forward end 38. In its preferred configuration, bore 52 is provided with several diameters which decrease in dimension from its rearward end 36 through a pair of bevelled openings 54 and 56. and terminating in a through hole 58 at its forward end 38.

Thus, bore 52 may be said to comprise a small hole 58, a nose bore portion 60, and a securing bore portion 62. An opening 64 transversely extends through a wall of contact body 30 from securing bore portion 62.

Secured also within bore portion 62 are a pair of alignment guides 66 and 68, which are respectively provided with bevelled entrances 70 and 72.

For assembly of an optical fibre conductor within contact body 30, an optical fibre conductor or waveguide 78 is first prepared.

Generally, such a conductor 78 includes a buffer material and a Kinar material both of which are removed for applicable lengths so as to expose the bare optical fiber 42 itself.

Removal of the buffer material may be made by use of a heated cutting edge and the Kinar material may be removed by a chemical such as acetone. Thereafter, stripped fibre 42 is cut by use of any suitable fiber cutting tool, such as described in The Bell System Technical Journal, Volume 52, No. 9, November, 1973, pages 1579-1588 in an article entitled, "Optical Fiber End Preparation for Low-loss Splices." After the fibre is properly cut, it is installed into contact body 30 by first passing it through pressure-sensitive seal 34, guides 66 and 68, hole 58, and precision hole 41 of bushing 40. By placing the end surface 40a of bushing 40 against the suitable stop of a fixture, terminus 80 of optical fibre 42 is made exactly flush with surface 40a. A bonding material is thereafter placed through opening 64 and into securing bore portion 62 lying between alignment guides 66 and 68. Such a bonding material may be of any suitable material such as epoxy or other adhesive or, if desired, a metallic slug such as of lead which is crimped uniformly against optical fibre 42. Contact 10 is then inserted within connector body 14 to establish a latching engagement between retaining clip 18 and annular portion 26.

An interface seal 82 is then placed over bushing 40 so that it is retained between bushing 40 and upstanding abutment end 44 of spacer 42. Such an interface seal 82 is also described in above-identified United States Patent No. 3,792,416.

Contact 12 may also be made in a similar fashion as contact 10; however. it is shown differently herein in order to show a means by which an optical fibre conductor 90 of different (and larger) diameter may be coupled to optical fibre 42. In this embodiment, contact body 32 has optical fibre conductor 90 secured thereto at its rearward end 92 by a tube 94 crimped against strength inducing threads 96 which are conventionally formed in optical fibre conductors. A laterally placed opening 98, similar to opening 64 in contact body 30, permits insertion of a bonding means for holding optical fibre conductor 90 precisely in place.

Contact 12 is provided with a bushing 100 which is similar to bushing 40 with the exception that bushing 100 has an internal opening 102 which is machined or otherwise formed to receive a forward portion 104 of optical fibre conductor 90. Also similar to bushing 40, bushing 100 is provided with a precision formed hole 106 whose diameter is precisely equal to that of the optical fibre.

The fibre terminus is made flush with end surface 100a of the bushing.

An alignment sleeve or tube 110 which is utilized to align bushings 40 and 100, is positioned on contact 12 in any convenient manner, such as by an indent 112 and an end 114 of sleeve 110 respectively abutting bushing 100 and a spacer ring 116. Spacer ring 116, in turn, contacts a shoulder 118 of contact body 32 as well as retainer ring 20. If desired, spacer ring 116 and contact body 32 may be made of a single machined part.

As best shown in Fig. 3, alignment sleeve 110 is provided with a slot 120 along its length and has a suitable number of openings 122 therein. These openings 122 are adapted to loosely retain a shim 124, shown in Fig. 4, which is provided with an aperture 125, and with tabs 126 that are adapted to reside within holes 122. Alignment sleeve 110 is made of a spring material and has an internal diameter which is slightly less, in its relaxed condition, than that of the outer peripheries 40b and 100b of bushings 40 and 100.

Because the outer peripheries of bushings 40 and 100 are precision dimensioned so that bushing peripheries 40b and 100b are as exactly concentric as possible with their holes 41 and 106, when the bushings are slid within alignment sleeve 110, holes 41 and 106 are precisely aligned which, in turn, precisely align the fibre termini.

In order to prevent contact and deleterious markings or other abrasion of the optical fibre termini, shim 124 contacts the end faces 40a and 100a respectively of bushings 40 and 100. Aperture 125 permits optical transmission between the fibres.

When bushings 40 and 100 are brought together on meeting of the connector bodies 14 and 16, there is a slight additional dimension of approximately 0.015 inches of travel remaining before the coupling hardware bottoms out. At this position, Belleville spring washers 50 begin to deflect and maintain a compression load between bushings 40 and 100 and, therefore, to maintain bushings 40 and 100 constantly against shim 124 so as not to vary the coupling distance between the termini of the optical fibres.

From the above description, it becomes evident that the present invention avoids the need to use an index matching material.

However, if such is desired, one may support it by shim 124 in aperture 125 thereof. If the material becomes csntaminated, the entire assembly of tube 110 and shim 124 may be replaced with another similar assembly with clean index matching material.

For coupling a pair of multiply-stranded optical fibre conductors 130 and 132 together, reference is directed to Figs. 5 and 6.

While the coupling hardware in this embodiment is the same as that described with respect to the single strand optical fibre conductor of Figs. 14, it is further required that each fibre terminus of one conductor is precisely aligned with a corresponding fibre terminus of the other conductor, in order to minimize or avoid transmission losses.

It has been suggested that one standard for enclosing multiply-stranded optical fibre conductors comprises an enclosure having an internal bore shaped in the form of a hexagon, in that a hexagon is a simple geometric shape and consumes less unoccupied space than a circle. It has further been suggested that a standard number of fibres comprise nineteen as best fitting within a hexagonal enclosure. The use of multiple strands ensures continued transmission in the event one or more strands break. Accordingly, Figs. 5 and 6 follow these suggested standards, although it is to be understood that the present invention is as adaptable to other numbers of fibre strands and to other housing internal bores having any polygonal or curved shape.

In the embodiments depicted in Figs. 5 and 6, conductors 130 and 132 respectively terminate in bundles of nineteen fibres whose termini 134 and 136 are shown and in which one or more of the conventional protective coatings and coverings may have been removed. Termini 134 and 136 are precisely retained respectively within bushings 138 and 140. Bushings 138 and 140 are similar to bushings 40 and 100 of Figs. 1--4, except that their through holes 142 and 144 have a non-circular shape, shown here in the standard hexagonal shape. Hexagonal holes 142 and 144 are precisely formed so that fibre termini 134 and 136 fit tightly therein, in order to prevent any detectable movement of the termini. Bushings 138 and 140 further differ from the earlier described bushings by having their peripheries 146 and 148 also shaped in the precise non-circular shape of holes 142 and 144. For the hexagonal shapes shown, each of the respective hexagonal sides of periphery 146 and hole 142 and the sides of periphery 148 and hole 144 are parallel and equidistantly spaced so that there is exact concentricity between the peripheries and the holes of the respective bushings and, therefore, between each of the fibre termini 134 and 136. Thus, for example, a centre row of five individual fibres 130a, l30h, 130c, 130d and 130e are precisely aligned with a corresponding centre row of five individual fibres 132a, 132b, 132c, 132d and 132e.

For coupling the fibres together in precise alignment, a sleeve 150 of spring material is provided with the precise non-circular shape of holes 142 and 144 and peripheries 146 and 148. Like sleeve 110 of Figs. 1--4, the internal periphery 152 of sleeve 150 is slightly smaller than bushing peripheries 146 and 148 and sleeve 150 is also provided with a longitudinally extending slot 154 so that bushings 146 and 148 can be slid into internal periphery 152. Because of the noncircular peripheral shapes involved, to avoid binding between the bushings and the sleeve in the event they are misaligned, both initially contacting surfaces of the bushings and the sleeve are rounded at 156 and 158 for a small angle such as 7" to 8" so that a slight total angular rotational movement of about 15 is encouraged between the bushings and the sleeve during mating engagements.

To minimize excessive forces that may be needed to rotate a plurality of contacts if the mating bushings and sleeve are not initially aligned, despite the presence of rounded portions 156 and 158, it is desired that there be relatively precise alignment of the bushings and their attached contacts within their connector body. Such alignment can be obtained by forming non-circular holes in the connector body or by using a detent on a contact which can reach into a neighbouring contact bore of the connector body to approximately angularly locate the contacts and bushings in their bores.

Also, as in Figs. 1--4, a shim of circular or corresponding non-circular shape is placed within sleeve 150 to prevent physical contact between the coupled fibres of conductors 130 and 132.

While the two preceding embodiments respectively of Figs. 1--4 and Figs. 5d describe coupling of optical fibre conductors.

it is preferred that the connector bodies be of a standard configuration which is adaptable to coupling optical as well as electrical or other electromagnetic signals. Such a standard configuration not only permits use of the same conductor body for all forms of electromagnetic signal-carrying conductor couplings but also enables one to mix such conductors and their contacts in the same connector body. Such a configuration is illustrated in Fig. 7 in which an optical fibre conductor 160 and its contact 162 and an electrical conductor 164 and its contact 166 are placed in a common connector body 168, in their respective bores 170. Optical fibre conductor 160 and its contact 162 may comprise any of the embodiments previously described, while electrical conductor 164 and its contact 166 may comprise those described in afore-mentioned U.S. patent 3,792,416. It is to be understood, however, that this concept encompasses any form of contact and conductor coupling, whether by the precise optical fibre and electrical conductors and contacts herein described or referred to or by any other conductors and contacts amenable to alternate or mixed reception in a connector body.

WHAT WE CLAIM IS: 1. A connector, coupling optical fibre conductors together at their termini wherein: said optical fibre conductors at their termini have respective enlargements whose peripheries are of a predetermined external dimension; a sleeve formed of resilient material, is formed with a longitudinal split, with the interior dimension of the sleeve being slightly smaller than the external dimension of said enlargement peripheries, and whose interior is mated to the said enlargements of said optical fibre termini, resiliently contacting and thereby commonly aligning both said conductors; and a spacer is loosely supported by and within said sleeve and between said enlargements to space said termini of said optical fibre conductors from mutual physical contact.

2. A connector as claimed in Claim 1 wherein each of said enlargements comprises a bushing.

3. A connector as claimed in Claim 1 or 2 wherein said spacer comprises a shim having an opening which is aligned with said optical fibre connectors, and said termini of said optical fibre conductors extend flush with terminal faces of said enlargements which abut said shim.

4. A connector as claimed in Claim 4, wherein tabs extend from said shim into openings in said sleeve for loosely supporting said shim in said sleeve.

5. A connector as claimed in Claims 1, 3 or 4, wherein two contact bodies are provided each having a through bore which extends from a rearward end to a forward end of the contact body to receive a respective one of said optical fibre conductors, and wherein said enlargements comprise bushings respectively secured to said forward ends of said contact bodies.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. the termini. Bushings 138 and 140 further differ from the earlier described bushings by having their peripheries 146 and 148 also shaped in the precise non-circular shape of holes 142 and 144. For the hexagonal shapes shown, each of the respective hexagonal sides of periphery 146 and hole 142 and the sides of periphery 148 and hole 144 are parallel and equidistantly spaced so that there is exact concentricity between the peripheries and the holes of the respective bushings and, therefore, between each of the fibre termini 134 and 136. Thus, for example, a centre row of five individual fibres 130a, l30h, 130c, 130d and 130e are precisely aligned with a corresponding centre row of five individual fibres 132a, 132b, 132c, 132d and 132e. For coupling the fibres together in precise alignment, a sleeve 150 of spring material is provided with the precise non-circular shape of holes 142 and 144 and peripheries 146 and 148. Like sleeve 110 of Figs. 1--4, the internal periphery 152 of sleeve 150 is slightly smaller than bushing peripheries 146 and 148 and sleeve 150 is also provided with a longitudinally extending slot 154 so that bushings 146 and 148 can be slid into internal periphery 152. Because of the noncircular peripheral shapes involved, to avoid binding between the bushings and the sleeve in the event they are misaligned, both initially contacting surfaces of the bushings and the sleeve are rounded at 156 and 158 for a small angle such as 7" to 8" so that a slight total angular rotational movement of about 15 is encouraged between the bushings and the sleeve during mating engagements. To minimize excessive forces that may be needed to rotate a plurality of contacts if the mating bushings and sleeve are not initially aligned, despite the presence of rounded portions 156 and 158, it is desired that there be relatively precise alignment of the bushings and their attached contacts within their connector body. Such alignment can be obtained by forming non-circular holes in the connector body or by using a detent on a contact which can reach into a neighbouring contact bore of the connector body to approximately angularly locate the contacts and bushings in their bores. Also, as in Figs. 1--4, a shim of circular or corresponding non-circular shape is placed within sleeve 150 to prevent physical contact between the coupled fibres of conductors 130 and 132. While the two preceding embodiments respectively of Figs. 1--4 and Figs. 5d describe coupling of optical fibre conductors. it is preferred that the connector bodies be of a standard configuration which is adaptable to coupling optical as well as electrical or other electromagnetic signals. Such a standard configuration not only permits use of the same conductor body for all forms of electromagnetic signal-carrying conductor couplings but also enables one to mix such conductors and their contacts in the same connector body. Such a configuration is illustrated in Fig. 7 in which an optical fibre conductor 160 and its contact 162 and an electrical conductor 164 and its contact 166 are placed in a common connector body 168, in their respective bores 170. Optical fibre conductor 160 and its contact 162 may comprise any of the embodiments previously described, while electrical conductor 164 and its contact 166 may comprise those described in afore-mentioned U.S. patent 3,792,416. It is to be understood, however, that this concept encompasses any form of contact and conductor coupling, whether by the precise optical fibre and electrical conductors and contacts herein described or referred to or by any other conductors and contacts amenable to alternate or mixed reception in a connector body. WHAT WE CLAIM IS:

1. A connector, coupling optical fibre conductors together at their termini wherein: said optical fibre conductors at their termini have respective enlargements whose peripheries are of a predetermined external dimension; a sleeve formed of resilient material, is formed with a longitudinal split, with the interior dimension of the sleeve being slightly smaller than the external dimension of said enlargement peripheries, and whose interior is mated to the said enlargements of said optical fibre termini, resiliently contacting and thereby commonly aligning both said conductors; and a spacer is loosely supported by and within said sleeve and between said enlargements to space said termini of said optical fibre conductors from mutual physical contact.

6. A connector as claimed in Claim 5,

wherein said bushings each have a through opening precisely dimensioned to a respective one of the optical fibre conductors and having a bevelled opening facing towards said rearward end and said bore of its respective contact body for guiding of said optical fibre conductor into the precisely dimensioned bushing opening.

7. A connector as claimed in Claim 6, wherein said optical fibre conductors are respectively supported in each of the contact body bores and are respective affixed to said contact bodies by a securing means placed in an opening extending transversely through a wall of each of said contact bodies for fixing said termini of said optical fibre conductors precisely with respect to said bushings.

8. A connector as claimed in Claim 7, wherein said securing means comprises an adhesive or a metal part crimped evenly to each said optical fibre conductor.

9. A connector as claimed in any of Claims 5 to 8, wherein a pair of alignment guides is provided in at least one of said contact bodies to support a respective one of said optical fibre conductors, said guides each having an opening therein whose dimensions generally equal that of said respective optical fibre conductor and said opening being bevelled in a direction facing towards said rearward end for facilitating insertion of said optical fibre conductor through the alignment guide opening.

10. A connector as claimed in Claim 7 or 8 and Claim 9, wherein said transversely extending opening and said securing means are positioned between said pair of alignment guides.

11. A connector as claimed in any of Claims 5 to 10, wherein said optical fibre conductors are respectively secured in their contact body bores against longitudinal movement therein so as to fix said termini of said optical fibre conductors precisely with respect to said bushings.

12. A connector as claimed in Claim 11, wherein said contact bodies and said bushings are secured in respective connector blocks, a pair of spacers are supported on at least one of said contact bodies with one of said spacers being in relatively non-resilient contact with said contact body and said connector block. and compressible resilient means are positioned between said spacers for exerting compression forces when said bushings in said connector blocks contact one another upon coupling together of said optical fibre connectors.

13. A connector as claimed in any of Claims 1 to 12, wherein said optical fibre conductors each include a bundle of fibres and each of said enlargements has a precisely shaped non-circular opening in which a respective said fibre bundle is terminated, the peripheries of said enlargements having configurations which precisely follow said precisely shaped non-circular openings for effecting concentricity of said fibre bundle respectively with said peripheries and said sleeve having an interior configuration which precisely follows said precisely shaped noncircular openings.

14. A connector as claimed in Claim 13 wherein said sleeve interior and said peripheries have rounded terminations for affording slight relative angular rotation between said enlargements and said sleeve during any initial coupling misalignment therebetween.

15. A connector as claimed in any of the preceding claims comprising a connector body having at least two bores therein respectively receiving an optical contact which is coupled to said optical fibre conductor and receiving an electrical contact which is couple to an electrical conductor.

16. A connector as claimed in Claim 15 wherein the bores in said connector body all have substantially the same configuration so that each bore is capable of receiving an electrical contact and is capable of receiving an optical contact.

17. A connector for optical fibre conductors substantially as herein described with reference to the accompanying drawings.