CA1096213A

CA1096213A - Optical fiber waveguide connector system

Info

Publication number: CA1096213A
Application number: CA305,142A
Authority: CA
Inventors: Norbert L. Moulin
Original assignee: Hughes Aircraft Co
Current assignee: Raytheon Co
Priority date: 1977-06-10
Filing date: 1978-06-09
Publication date: 1981-02-24
Also published as: JPS545748A; DE2824507C2; GB1601277A; JPS57157911U; DE2824507A1; JPS6037527Y2; FR2394103A1; FR2394103B1

Abstract

ABSTRACT OF THE DISCLOSURE

Precise alignment, required for a low-loss electro-magnetic interconnection between single and multiple stranded optical fiber conductors or waveguides, is achieved in a conventional electrical connector block. A pair of guide bushings having precise outer dimensions are secured respectively to the termini of the optical fiber conductors and these bushings, in their respective connector blocks, are adapted for insertion into a split tube having a precisely dimensioned inner diameter. The optical fiber conductors, being concentric with the bushings, thereby are precisely interconnected.
For single fibers, the bushings and the split tube are cylindrical. for multiple stranded fibers or fiber bundles, the bushings and the split tube have identical polygonal cross-sections, which match precisely identical polygonally shaped fiber-receiving openings in the bushings. Physical contact between the electromagnetically coupled fiber optic conductors is prevented by a flat annular shim which is loosely secured-to the split tube and contacted by the bushings.

Description

Z~3 BACKGROUMD OF THE INVENTION

2 1. Field of the Invention

3 The present invention relates to means for electro-

4 magnetically coupling sinqle and multiple strand optical fiber conducto~rs or waveguides.
~ 2. ~ tion of ~he Prior Art and B ~ nsiderations 7 A fundamental problem in the interconnection of optical`
8 fiber conductors is the alignment of the fibers of the two 9 conductors. A further problem is the ability to maintain suci alignmen~ under repeated engagement and disengagement cycles.
11 It is desirable that this precise couplln~ be accomplished 12 without the use of index matching materials, since they are 13 prone to contamination and could degrade coupling efficiency 14 after several en~agement and separation cycl~sO Typically, such conductors have a diameter of approximately 0.005 inches 16 (Q.127 mm~. Because even minute misal,ignment between mating 17 optical fiber conductors results in significant transmission 18 loss, it is imperative that they be precisely aligned. With 19 very small dlam,eter conductorsj it is apparent that the 20 alignment task for si~lgle strand fibers is formidable.
21 Ali~nment between~multiple strand fibers i5 even more difficult.
22 Presently known optical fiber lnterconnects are known, 23 and their los5es have been advertised to be 0.5 db to 3~5 db.
24 Such a variation in loss means that~ it is no~ possible ~s to obtain effectively repeatable alignment. ~
26 It is further deslrable to prevent the ends of the 27 optical fiber conductors to contact and, therefore, to 28 be scratched. Such 5cratching or other damage causes the 2~

~g~Z3~3 . i 1 liyht being transmitted to be diffused with consequential 2 loss in light transmission.
3 In addition to these and other considerations, it is 4 also desirable that the connector bodies receiving the optical fiber conductors be capable of receiving, at the same time, 6 conventional electrical conductors and contacts so that 7 mixes of the two electromagnetic signal carrying means can 8 be realized. As a corollary, specialization in parts and g stock and manufacturing equipmen~ can be avoided if the same connector blocks and other termination hardware are used for 11 coupling of both electrical as well as optical conductors.

13 S~ Or 5~ IN.~nllON
14 The present invention overcomes or avoids these and lS other problems and meets the considerations above outlined 16 by providing for a split sleeve which accepts alignment 17 bushings attached to each end of the optical Eiber connectors.
18 The optical fibers are received in holes in the bushings 19 and the holes are precisely concentric with the bushing peripheries. Therefore, the bushings as well as the sleeve 21 must be precisely dimensioned, whether in circular or 22 polygollal cross-section (corresponding identically in shape 23 to that o~ the holes in the bushings), to provide for the 24 greatest possible concentricity and actual alignment between the optical ~ibers to be coupled. To mate and align 26 the bushings, they are slid into the split sleeve which acts 27 as a spring. Thus, alignment of the bushing~ automatically 28 and precisely aligns the optical fibers and permits couplin~

~i96;~:~3 1 and uncoupling cycles. To prevent contact of the conductors 2 at the inter~ace between the bushlngs, a shim or similar 3 spacing means is positioned in the sleeve and comes into 4 contact with only the bushings. The optical fiber conductors are received in contacts which are configured to permit 6 their insertion into conventional electrical connector 7 bodies. Thus, mixes o~ optical and electrical conductors 8 and couplings are obtainable in the same conductor block.
9 It is therefore, an object of the present invention to provide for an electromagnetic coupling between optical iber conductors.
12 Another object is to provide for a simple yet precise 13 alignment between such optical fiber conductors.
14 Another object is to provide for repeated coupling and uncoupling of the conductors without degradation of the 16 alignment.
17 Another object is to provide ~or such alignment 18 which does not depend on the use of index matching materials.
1~ Anot~.er object is to prevent physical contact between the coupled optical fiber conductors.
21 ~nother object is to provide for use of connector 22 bodies for mixed or alternative reception of different electro-23 magnetic signal carrying conductors and/or contacts, such as 24 optical and electrical signals.
In one aspect of theinvention there is provided 26 a connector for electromagnetically coupling optical fiber 27 conductors together at their termini,~ wherein said optical 28 fiber conductors at~thelr respective termini have enlargements 29 whose peripheries are precisely dimensioned; a sleeve is formed of resilient material and is longitudinally split, with its 31 interior dimension being slightly smaller than the dimensions 6~3 1 of said enlargement peripheries, and whose inkerior is mated 2 to the precisely dimensioned enlargements of said optical 3 fiber termini to contact and thereby commonly align both 4 conductors; and a spacer is loosely supported by and within said sleeve and between said enlargements to space said 6 termini of said optical fiber conductors from mutual 7 physical contact.
8 Other aims and objects as well as a more complete 9 understanding of the present invention will appear from the following explanation of exemplary embodiments and the 11 accompanying drawings thereof.

. -~a-.. i ^~

.... , . .. ' : ' .' ' ' : - , , , ., :
. - - . :- . .

62~

BRIEF DE_CRIPTION Ol? TE~E DRAWINGS
2 Figs. la and lb are views in cross-section, of a pair 3 of connector bodies with single strand optical fiber conductors 4 and contact bodies therein coupled together, with one strand S having a larger diameter than the other;
6 Fig. 2 is a perspective view of one of the contact bodies 7 of Fig. 1 with its optical fiber conductor terminated therein;
8 Fig. 3 is a perspective view of the split tube or sleeve 9 shown in Fig. 1 used to obtain precise alignment between the coupled optical fiber conductors;
11 Fig. 4 is a view of the shim used to prevent contact 12 between the coupled optical fiber conductors of Fig. l;
13 Fig. 5 ls an end view of a second embodiment of the 14 present invention illustrating a hexagonally shaped bushing used to terminate a conductor having multiple strands of 16 optical fibers;
17 Fig. ~ depicts a pair of bushings, as shown in Fig. ~, 18 coupling multiple 6tranded optical fiber conductors together 19 with a hexagonally shaped split sleeve properly aligning the fiber termini: and 21 Fig. 7 depicts the combination where both electrical wlres 22 and cptical fibers are positioned in a common connector body.

24 DESCRIPTION OF THE PREFÆRRED EMBODIMENTS
While the preferred embodiments re]ate to connecting 26 optical fiber conductors in much th~e same manner that electrical 27 wlres are connected in conventional electrical connectors, 28 speclfic uses may requlre qulte ~lfferent approaches. Therefore, S
. .

, , 2~3 1 it is to be understood that other config-lrations lying 2 within the scope of the present invention are also intended 3 to be included.
4 Accordingly, with reference to Figs. 1-4, a pair of contacts 10 and 12 are positioned within their respective 6 connector bodies 14 and 16 in any conventional manner, such 7 as by retaining clips 18 and 20. These retaining clips 8 reside within recesses 22 and 24 of their respective contacts 9 and are adapted to engage annular portions 26 and 28 of their connector bodies.
11 Each contact 10 and 12 includes a con~act body 30 and 32 12 with a pressure-sensitive wire seal, such as seal 34, attached 13 at the rearward end 36 of contact body 30. Such a pressure-14 sensitive wire seal 34 is described in United States Patent No.
3,792,416, which also utilizes similar retaining clips 18.
16 At its opposite or forward end 38, contact body~ 30 carries 17 an alignment bushing 40, which is secured to end 38 in 18 any convenient manner. Bushing 40 is provided with a precisely 19 formed hole 41 for receiving the terminus of an optical fiber 42.
The diameter of hole 41 is as close as that of fiber 42.
21 Ab~tting against alignment hushing 40 is a spring 22 spacer 43, which is provided with an upstanding spring 23 abutment end 44. Spaced from upstanding abutment end 44 24 is a second spacer ring 96 which abuts against a surface 48 o contact body 30. Positioned between spacers 43 and 46 26 are a plurality~of spring washers 50, such as four Belleville 27 spring washers. The purpose of these spring washers will 28 become evident herelnafter.

.

~96~ 3 1 Contact body 30 is further provided with a through 2 bore 52 extending from its rearward end 36 to its forward 3 end 38. In its preferred configuration, bore 52 is provided 4 ~ith several diameters which decrease in dimension from its rearward end 36 through a pair of bevelled openings 54 and 6~ 56, and terminating in a through hole 58 at its forward end 38.
7 Thus, bore 52 may be said to comprise a small hole 58, a nose 8 bore portion 60, and a securing bore portion 62. An opening 64 g transversely extends through a wall of con~act body 30 from securing bore portion 62. Secured also within bore 11 portion 62 are a pair of alignment guides 66 and 68, which 12 are respectively provided i~ikh bevelled entrances 70 and 72.
13 For assembly of an optical fiber conductor within 14 contact body 30, an optical fiber conductor or waveguide 78 is first prepared. Generally, such a conductor 78 includes a buffer 16 material and a ~ynar material both of which are removed 17 for applicable lengths 50 as to expose the bare optical 18 fiber 42 itself. Removal of the buffer material may be made 19 by use of a heated cutting edge and the K~nar material may be removed by a chemical such as acetone. Thereafter, 21 stripped fiber 42 is cut by use of any suitable fiber 22 cutting tool, such as described in The Bell System Technical 23 Journal, Volume 52, No. 9, November, 1973, pages 1579-1588 `24 in an article entitled, "Optical Fiber Ænd Preparation for ~5 Low-Loss Splices."
26 After the fiber is properly cut, it is installed into 27 contact body 30 by first passing it through pressure-sensitive 28 seal 34, gu1des 66 and 68, hole 58, and precision hole 41 *"KYNAR" is a trademark of Penwalt Corporatio~ or fluorocarbon material -~r~

.. . .. . .. . .. . , . . , . .. . . . . , . . . . . . _ ': . . ', ': .

~ 6 ~

1 of bushing 40. By placing the end surface 40a of bushing 40 2 aqainst the suitable stop of a fixture, terminus 80 of optical 3 fiber 42 is made exactly flush with surface 40a. A bondinq 4 material is thereafter placed through opening 64 and into securing bore portion 62 lying between alignment guides 66 and 6~ 68. Such a bonding material may be of any suitable material 7 such as epoxy or other adhesive or, if desired, a metallic 8 slug such as of lead which is crimped uniformly against 9 optical ~iber 42. Contact 10 is then inserted wlthin connector body 14 to establish a latching engagement between retaining 11 clip 18 and annular portion 26.
12 An interface seal 82 is then placed over bushing 40 13 so that it is retained between bushing 40 and upstanding 14 abutment end 44 of spacer 42. Such an interface seal 82 is also described in above-identified United States Patent No.
16 3,792,4]6.
17 Contact 12 may also be made in a similar fashion as 18 contact 10; however, it is shown differently herein in 19 order to show a means by which an optical fiber conductor 90 of different (and larger) diameter may be coupled to optical 21 fiber 42. In this embodiment, contact body 32 has optical 22 fiber conductor 90 secured thereto at its rearward end 92 23` by a tube 94 crimped against strength inducing threads 96 ~4 which are conventionally formed in optical ~iber conductors.
A laterally placed opening 98, similar to opening 64 in 26 contact body 30, permlts insertion of a bonding means for 27 holding optical fiber conductor 90 precisely in place.

Z~3 1 Contact 12 is provided with a b~shing 100 which is 2 similar to bushing 40 with the exception that bushing 100 3 has an internal opening 102 which is machined or otherwise 4 formed to receive a forward portion 104 of optical fiber S conductor 90. Also similar to bushing 40~ bushing 100 is 6 provided with a precision forJned hole 106 whose diameter is 7 precisely equal to that of the optical fiber. The fiber 8 terminus is made flush with end surface lOOa of the bushing.
9 An alignment sleeve or tube 110 which is utilized to ~10 align bushings 40 and 100, is positioned on contact 12 11 in any convenient manner, such as by an indent 112 and 12 an end 114 of sleeve 110 respectively abutting bushing 100 13 and a spacer rin~ 116. Spacer ring 116, in turn, contacts 14 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 16 a single machined part.
17 As best shown in Fig. 3, alignment sleeve 110 is 1~ provided wi-th a slot 120 along its length and has a suitable 19 number of openings 122 therein. These openings 122 are adapted to loosely retain a shim 124, shown in Fig. 4J
~1 which is provided with an aperture 125, and with tabs 126 22 ~hat are adapted to reside withi~ holes 122. Alignment 23 sleeve 110 is made of a spring material and has an internal ~4 diameter which is slightly less, in its relaxed condition, than that of the outer peripheries 40b and lOOb of bushings 26 40 and 100. Because the outer perlpheries o~ bushings 40 27 and 100 are precision dimensioned so that bushing peripheries 28 40b and lOOb are as exactly concentric as possible with - . ~

96~3 1 ~heir holes 41 and 106, when the bushings are slid within 2 alignment sleeve 110, holes 41 and 106 are precisely aligned 3 which, in turn, precisely align the fiber termini.
4 In order to prevent contact and deleterious markings or other abrasion of the optical fiber termini, shim 124 6 contacts the end faces 40a and lOOa respectively of bushings 40 7 and 100. Aperture 125 permits optical transmission between 8 the fibers.
9 When bushings 40 and 100 are brought together on meeting of the connector bodies 14 and 16, there is a sli~ht 11 additional dimension of approximately 0.015 inches of travel 12 remaining before the coupling hardware bottoms out. A~
13 this position, Belleville spring washers 50 begin to 14 deflect and maintain a compression load between bushings ~0 and 100 and, therefore, to maintain bushings 40 and 100 16 constantly against shim 124 so as no~ to vary the coupling 17 distance between the termini of the optical fibers.
18 From the above description, it becomes evident that the 19 present invention avoids the need to use an lndex matching material. However, if such is desired, one may support it 21 by shim 124 in aperture 125 thereof. If the materlal becomes 22 contaminated, the entire assembly of tube 110 and shim 124 may 23 be replaced with another similar assembly with clean index 24 matching material.
For coupling a pair of multiply-stranded optical fiber 2~ conductors 130 and 132 together 7 reference is directed to 27 Figs. 5 and 6. While the coupling hardware in this embodiment 28 is the same as that described with respect~to the single , .

1 strand optical fiber conductor of Figs. 1-4, it is further 2 required that each fiber terminus of one cond-lctor is precisely 3 aligned ~ith a corresponding fiber terminus of the other 4 conductor, in order to minimize or avoid transmission losses.

5` It has been suggested that one standard for enclosing

6~ multiply-stranded optical fiber conductors comprises an enclosure

7 having an internal bore sha~ed in the form of a hexagon, in that

8 a hexagon is a simple geometric shape and consumes less g unoccupied space than a circle. It has further been suggested that a standard number o fibers comprise nineteen as best 11 fitting within a hexagonal enclosure. The use of multiple 12 strands ensures continued transmission in the event one or 13 more strands break. Accordingly, Figs. 5 and 6 follow these 14 suggested standards, although it is to be understood that the present invention is as adaptable to other numbers 16 of fiber strands and to other housing internal bores having 17 any polygonal or curved shape.
18 In the embodiments~depicted in Figs. 5 and 6, conductors 1~ 130 and 132 respectively terminate in bundles of nineteen fibers whose termini 134 and 136 are shown and in which ~1 one or more of the conventional protective coatings and 22 coverin~s may have been removed. Termini 134 and 136 are precisely 23 retained respectively ~ithin bushings 138 and 140. Bushings '24 138 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 26 shape, shown here in the standard hexagonal shape~ Hexagonal 27 holes 142 and 144 are precisely formed so that fiber termini 28 134 and 136 fit tightly therein,,in order to prevent any ..

.

1 detectable movement of the termini. Bushings 138 and 140 2 further differ from the earlier described bushings by having 3 their peripheries 146 and 148 also shaped in the precise 4 non-circular shape of holes 142 and 144. For the hexagona.
shapes sho~n, each of the respective hexagonal sides of 6 periphery 146 and hole 142 and the sides of periphery 148 7 and hole 144 are parallel and equidistantly spaced so that 8 there is exact concentricity between the peripheries and the

9 holes of the respective bushings and, therefore, between each of the fiber termini 134 and 136. Thus, for example, a center 11 row of five individual fibers 130a, 130b, 130c, 130d and 130e 12 are precisely aligned with a corresponding center row of five 13 individual fibers 132a, 132b, 132c, 132d and 132e.
14 For coupling the fibers together in precise alignment, a sleeve 150 of spring material is provided with the precise 16 non~circular shape of holes 142 and 144 and peripheries 17 146 and 14~. Like sleeve 110 of Figs. 1-4, the internal 18 periphery 152 of sleeve 150 is slightly smaller than bushin~
19 peripheries 1~6 and 148 and sleeve 150 is also provided with a longitudinally extending slot 154 so that bushings 21 146 and 148 can be slid into internal periphery 152. Because 22 of the non-circular peripheral s~apes involved, tc avoid 23 binding between the bushings and the sleeve in the everlt 24 they are misaligned, both initially contacting surfaces of the bushings and the sleeve are xounded at 156 and 158 26 for a small angle such as 7 to 8 so tha~ a slight total 27 angular rotational movement of about 15 is encouraged between 28 the bushings and the sleeve during matiny engagements.

` ' .

Z~3 .

1 To minimize excessive forces that may be needed to 2 rotate a plurality of contacts if the mating bushings and 3 sleeve a~e not initially aligned, despite the presence of 4 rounded por~ions 156 and 158, it is desired that there be relatively precise alignment of the bushings and t,heir 6 attached contacts within their connector body. Such alignment 7 can be obtained by forming non-circular holes in the connector 8 body or by using a detent on a contact which can reach 9 into a neighboring contact bore of the connector body to approximately angularly locate the contacts and bushings 11 in their bores.
12 Also, as in Figs. 1-~, a shim of circular or corresponding 13 non-circular shape is placed within sleeve 150 to prevent 14 physical contact between the coupled fibèrs of conductors 130 and 132.
16 While the two preceeding embodiments respectively 17 of Figs. 1-4 and Figs. 5-6 describe coupling of optical 18 fiber conductors, it is preferred that the connector bodies 19 be of a standard configuration which is adaptable to coupling optical as well as electrical or other electromagnetic signals.
21 Such a standard conflguration not only permits use of the ~2 same conductor body for all forms of electromagnetic 23 signal-carrying conductor couplings bllt also enables one to mix 24 such conductors and their contacts in the ~ame connector body~ Such a configuration is illustrated in Fig. 7 in 26 which an optical fiber conductor 160 and its contact 162 and 27 an electrical conductor 164 and its contact 166 are placed -28 in a common connector body 168, in their respective bores 170 .

Ç;2~3 1 Optical fiber conductor 160 and its contact 16~ may comprise 2 any of the embodiments previously described, while electrical 3 conductor 164 and its contact 166 may comprise those described 4 in afore-mentioned patent number 3J792,416. It is to be understood, ho~ever, that this concept encompasses any form 6 -of contact and conductor coupling, whether by the precise 7 optical fiber and elec~rical conductors and contacts herein 8 described or referred to or by any other conduc~ors and 9 contacts amenable to alternate or mixed reception in a connector body.
11 Although the invention has been described with 12 reference to particular embodiments thereof, it should 13 be realized that various changes and modifications can 14 be made therein without departing from the spirit and scope of the invention.

~ 14 ~

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A connector for electromagnetically coupling optical fiber conductors together at their termini, wherein said optical fiber conductors at their respective termini have enlargements whose peripheries are precisely dimensioned; a sleeve is formed of resilient material and is longitudinally split, with its interior dimension being slightly smaller than the dimensions of said enlargement peripheries, and whose interior is mated to the precisely dimensioned enlargements of said optical fiber termini to contact and thereby commonly align both conductors; and a spacer is loosely supported by and within said sleeve and between said enlargements to space said termini of said optical fiber 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, wherein said spacer comprises a shim having an opening which is aligned with said optical fiber connectors, and said termini of said optical fiber conductors extend flush with terminal faces of said enlargements which abut said shim.

4. A connector as claimed in Claim 3, 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 Claim 1, 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 fiber conductors, and wherein said enlargements comprise bushings respectively secured to said forward ends of said contact bodies.

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 fiber conductors and having a beveled opening facing towards said rearward end and said bore of its respective contact body for guiding of said optical fiber conductor into the precisely dimensioned bushing opening.

7. A connector as claimed in Claim 6, wherein said optical fiber conductors are respectively supported in each of the contact body bores and are respectively 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 fiber conductors precisely with respect to said bushings.

8. A connector as claimed in Claim 7, wherein said securing means comprises a bonding material.

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

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

11. A connector as claimed in Claim 5, wherein said optical fiber conductors are respectively secured in their contact body bores against longitudinal movement therein so as to fix said termini of said optical fiber 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 fiber connectors.

13. A connector as claimed in Claim 1, wherein said optical fiber conductors each include a bundle of fibers and each of said enlargements has a precisely shaped non-circular opening in which a respective fiber bundle is terminated, the peripheries of said enlargements having configurations which precisely follow said precisely shaped non-circular openings for effecting concentricity of said fiber bundles respectively with said peripheries and said sleeve having an interior configuration which precisely follows said precisely shaped non-circular 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 Claim 1, comprising a connector body having at least two bores therein respectively receiving an optical contact which is coupled to said optical fiber conductor and receiving an electrical contact which is coupled 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.