GB1598732A - Coupling optical fibres - Google Patents

Description

(54) COUPLING OPTICAL FIBRES (71) We, E. I. Du PONT DE NEMOURS AND COMPANY, a corporation organised and existing under the laws of the State of Delaware, United States of America, of Wilmington, Delaware, 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 terminal for an optical fibre and to a connector for optical fibres.

The connector of the invention permits the transmission of light from the output of one optical device to the input of another and, more particularly the end-to-end coupling of fibres in the path of transmission.

An optical fibre connector with flared sockets leading to a bore has been disclosed by Martin in United States Patent No.

3,948,582. The flared sockets receive conical plugs from which fibres extend into abutting relationship in the bore. Each plug has a bore through which a fibre is threaded. Then, the fibre must be cemented in place. In addition to the difficulties inherent in cementing the fibre, the probabilities of achieving alignment in the plug and avoiding damage to the fibre are low.

According to the present invention there is provided a terminal for an optical fibre, comprising a pair of mating elongate channel members, each split into a plurality of fingers at one end, said fingers terminating in jaws adapted to engage and laterally locate an optical fibre extending through a channel defined by said members.

There is also provided in accordance with the invention a connector for optical fibres, comprising a body having a pair of opposed aligned sockets each leading to an interconnecting bore, a terminal as set forth above adapted to be received in each socket, and inter-engaging latch means on said terminals and said body for holding the terminals in said sockets An embodiment of the invention is hereinafter described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is an enlarged exploded perspective illustration of a connector body and one terminal; Figure 2 is a fragmentary plan view of the connector body shown in Fig. 1, with two terminals inserted therein, parts having been broken away and shown in section to reveal details of construction: Figure 3 is a fragmentary sectional view taken on line 3-3 in Fig. 2, except that only one terminal appears and it is shown in its entirety; Fig. 4 is a fragmentary enlarged sectional view of the connector, taken on line 3-3 in Fig. 2, and shows the location of optical fibres in the assembled connector; Figs. 5 and 6 are perspective and side views, respectively, of one channel member of the terminal of Figs. 1 to 4.

Fig. 7 is an end view of the channel member shown in Figs. 5 and 6; and Fig. 8 is a side view of a channel member with an optical fibre shown as it is located during assembly of a terminal.

A fibre optics connector includes a body 10 having opposed pairs of sockets 12, each adapted to receive and seat a terminal 14.

Body 10 is assembled from mating sections 16 18 and each terminal 14 from a pair af identical channel members 20. Sections 16, 18 have integral pins 22 that press fit in comple- mentary holes 23. Section 18 has horizontal and vertical mounting flanges 24, 26. At each end of body 10, three pairs of fingers 28, 30 and opposed pairs of latches 32, 34 define rectangular entries to the sockets 12.

Body 10 and terminals 14 are moulded from a polycarbonate and a polyester, respectively.

Other platics are suitable, e.g., acrylonitrilebutadiene-styrene (ABS), phenylene oxide, polyether sulphones and mixtures of ABS with a polycarbonate. The plastics from which the terminals are moulded can be reinforced, e.g. with glass fibres.

Referring to Fig. 3, each socket 12 includes an elongate passage 36 that is circular in crosssection. Passage 36 extends to a step 38 from which socket 12 continues inwardly through a conically tapered seat 40 and a counterbore 42 of circular cross-section to another counterbore 44 which is referred to herein as a bore that interconnects a pair of opposed, aligned sockets 12.

As shown in Figs. 5 to 7, each channel member 20 has a flared channel 46 on its inner surface 48. Intermediate its ends, at a shoulder 50, the outside geometry of the channel member changes from rectilinear surfaces to a rounded exterior in a length 52.

Length 52 is adapted for insertion into a socket 12 and has its free end split at 54 into flexible fingers 56, 58. At the end of each finger, there is a jaw 60 with a tapered outer surface 62 and an enlarged segment 64 having a cylindrical exterior. Surfaces 62, 64 are separated by a step 66.

In the termination of an optical fibre, a channel member 20 is located in a fixture.

Then, an optical fibre 68 with the polymeric jacket 70 stripped from its end is placed on the channel member, as shown in Fig. 8, with the stripped end extending beyond the squared ends ofjaws 60 and with the jacket 70 resting in channel 46. Next, a second channel member 20 is mated with and latched to the first.

In this respect, each channel member 20 has a central latch 72 and an end latch 74. Each latch 72 catches in a complementary recess 76 and each latch 74 in a complementary recess 78 on the mated channel member 20. With the channel members so latched, the jacketed fibre is gripped in channels 46. As best shown in Figs. 7 and 8, channels 46 are dish-shaped.

Their width adjacent shoulder 50 is greater than the diameter of a jacketed fibre and their depth slightly less than half the diameter of a jacketed fibre. This relationship makes it easier to place and grip the jacket during assembly.

With the channel members latched and held, the stripped end is cut in close proximity to but protruding slightly beyond the squared ends of the jaws 60 (Fig. 4). Channels 46 can, of course, be dimensioned to grip the unjacketed end of a fibre. The degree of flex in fingers 56, 58 is a design feature that can be varied to provide a loose fit or light pressure on a fibre 68 as channel members 20 are latched. Thus, with the split terminals disclosed herein, the stripped ends of optical fibres can be terminated accurately without being threaded through small passages or otherwise exposed to abrasive contacts that frequently lead to scratches or fractures. The possibility of scratches and fractures is further minimized by not having to cut the end of the fibre until after its termination and by cutting the relatively stifflengthcloseto the jaws.

When a terminal is inserted, rotational alignment is maintained by the fit of the rectilinear length to the rear of shoulders 50 in the rectangular entries defined by fingers 28, 30 and latches 32, 34 on sections 16, 18 of body 10.

Referring to Figs. 3 and 6, each latch 72 has a gradually sloped leading edge and a sharply sloped trailing edge. Upon insertion, the leading edges of latches 72 cam latches 32, 34 and the latter catch on the trailing edges. As shown in Fig. 3, the catch surfaces on latches 32, 34 are disposed for engagement with the trailing edges on latches 72. In the event axial forces are supplied to a fibre, the cooperating edges on the latches permit a terminal to eject itself before the applied force reaches the breaking strength of the fibre. The fibre can be moved with respect to inserted terminals without breakage because of the flared ends of channels 46. In this respect, the maximum extent of flare in the channels is less than the angle of bend at which the fibres break.

As the terminal is inserted, the interrupted cylindrical surface presented by segments 64 aligns the terminal with respect to the socket 12 and bore 44. The tapered surfaces 62 on jaws 60 engage seat 40 and move together to align fibre 68 with bore 44. By design, bore 44 should have a somewhat larger diameter than the fibre 68. With the terminal already in alignment with socket 12 and bore 44, the engagement of surfaces 62 with seat 40 ensures alignment of the fibre end in jaws 60 and, therefore, with the bore 44. Thus, the protruding ends of the fibres do not touch body 10 and, accordingly, are not damaged.

When another terminal 14 has been inserted in the opposed socket 12, the spaced ends of two fibres are aligned and light can be transmitted effectively from one to the other through bore 44.

The gap between the two fibres should not exceed the diameter of a stripped fibre end.

As a minimum, the protruding ends of the fibres should not contact each other. If the fibre ends are closely spaced, an acceptable level of light loss can be achieved with asmoulded parts. As the gap is increased, the rate at which light loss increases is reduced by augmenting reflectivity in the bore, e.g., by polising the moulded bore or by depositing aluminium on the surface of the bore by cathode sputtering. Other coating materials such as gold and multilayer dielectric films are suitable. Other deposition techniques include vacuum evaporation and chemical vapour deposition.

The connector shown in Fig. 1 has two pairs of aligned sockets 12. As such, it is particularly suitable for use in coupling reinforced and jacketed cables of two jacketed fibres. Such a cable is available from the applicant and is identified as PFX-P240R.

The cable contains two plastics optical fibres, each of which consists of a polymethyl methacrylate core in a polymeric cladding of lower refractive index. Jackets on the individual fibres and on the cable are of a flame retardant polyester elastomer. The connector is, of course, adapted to couple uncabled fibres and fibres of other compositions, e.g*, pure silica, doped silica, glass or a polystyrene core clad with an acrylic.

WHAT WE CLAIM IS 1. A terminal for an optical fibre, comprising a pair of mating elongate channel members, each split into a plurality of fingers at one end, said fingers terminating in jaws adapted to engage and laterally locate an optical fibre extending through a channel defined by said members.

2. A terminal as claimed in Claim 1, further comprising integral latch means on at least one of said members for holding the members mated.

3. A terminal as claimed in Claim 1 or 2, wherein said fingers are flexible and adjacent fingers are spaced from one another.

4. A terminal as claimed in any preceding claim, wherein said jaws have tapered outer surfaces.

5. A connector for optical fibres, comprising a body having a pair of opposed aligned sockets each leading to an interconnecting bore, a terminal as claimed in any preceding claim adapted to be received in each socket, and inter-engaging latch means on said terminals and saidbodyforholding the terminals in said sockets.

6. A connector as claimed in claim 5, wherein each socket has a tapered seat adjacent said bore and said jaws have tapered outer surfaces adapted to engage said tapered seats.

7. A connector as claimed in Claim 6, wherein each socket has a counterbore between said tapered seat and said bore, the fingers on each terminal having squared ends adapted to be received within said counterbore.

8. A connector as claimed in Claim 6 or 7 wherein said jaws have segments of increased radial extent adjacent said tapered outer surfaces, said segments presenting an interrupted cylindrical surface adapted to slidably engage the said body within a said socket as each terminal is inserted.

9. A terminal for an optical fibre substantially as herein described with reference to the accompanying drawings.

10. A connector for optical fibres substantially as herein described with reference to the accompanying drawings.

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

Claims (10)

**WARNING** start of CLMS field may overlap end of DESC **. retardant polyester elastomer. The connector is, of course, adapted to couple uncabled fibres and fibres of other compositions, e.g*, pure silica, doped silica, glass or a polystyrene core clad with an acrylic. WHAT WE CLAIM IS

1. A terminal for an optical fibre, comprising a pair of mating elongate channel members, each split into a plurality of fingers at one end, said fingers terminating in jaws adapted to engage and laterally locate an optical fibre extending through a channel defined by said members.

2. A terminal as claimed in Claim 1, further comprising integral latch means on at least one of said members for holding the members mated.

3. A terminal as claimed in Claim 1 or 2, wherein said fingers are flexible and adjacent fingers are spaced from one another.

4. A terminal as claimed in any preceding claim, wherein said jaws have tapered outer surfaces.

5. A connector for optical fibres, comprising a body having a pair of opposed aligned sockets each leading to an interconnecting bore, a terminal as claimed in any preceding claim adapted to be received in each socket, and inter-engaging latch means on said terminals and saidbodyforholding the terminals in said sockets.

6. A connector as claimed in claim 5, wherein each socket has a tapered seat adjacent said bore and said jaws have tapered outer surfaces adapted to engage said tapered seats.

7. A connector as claimed in Claim 6, wherein each socket has a counterbore between said tapered seat and said bore, the fingers on each terminal having squared ends adapted to be received within said counterbore.

8. A connector as claimed in Claim 6 or 7 wherein said jaws have segments of increased radial extent adjacent said tapered outer surfaces, said segments presenting an interrupted cylindrical surface adapted to slidably engage the said body within a said socket as each terminal is inserted.

9. A terminal for an optical fibre substantially as herein described with reference to the accompanying drawings.

10. A connector for optical fibres substantially as herein described with reference to the accompanying drawings.