GB1572503A

GB1572503A - Optical waveguide coupling

Info

Publication number: GB1572503A
Application number: GB1134577A
Authority: GB
Original assignee: Smiths Group PLC
Current assignee: Smiths Group PLC
Priority date: 1977-03-17
Filing date: 1977-03-17
Publication date: 1980-07-30

Description

(54) OPTICAL WAVEGUIDE COUPLING (71) We, SMITHS INDUSTRIES LIMITED, a British Company of Cricklewood, London NW2 6JN, 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 statements: This invention relates to optical waveguide couplings.

Various couplings have been proposed for coupling optical fibres or bundles of optical fibres, where the ends of the waveguides abut one another. This is commonly referred to as splicing of the optical fibres. It is necessary axially to align the ends of the individual fibres or bundles of optical fibres with one another to provide the required degree of optical coupling between the fibres, and, heretofor, various forms of coupling devices have been proposed to provide this axial alignment and thus maximise the optical coupling between the fibres. Such coupling devices are often rather complicated and thus relatively expensive or involve the use of somewhat complicated methods of mounting the fibre ends in the coupling devices.

It is an object of the present invention to provide an optical waveguide coupling which substantially overcomes the aforementioned disadvantages.

According to one aspect of the present invention there is provided an optical waveguide coupling having a connector defining a longitudinal bore which is arranged to receive the ends of a pair of optical waveguides and to align those waveguide ends with one another, wherein the connector comprises a support member and a multiplicity of flexible elongate members mounted on the support member and defining the said longitudinal bore, the elongate members being spaced apart about the axis of the longitudinal bore and being individually deformable in an outwards direction, and wherein the coupling comprises means for engaging the ends of a pair of optical waveguides inserted in the longitudi nal bore to anchor the waveguide ends in the connector.

In use the said elongate members are deformed outwardly by inserting into the ends of the said longitudinal bore respective ends of a pair of optical waveguides so that the elongate members resiliently engage the ends of the optical waveguides and maintain them in alignment with one another.

The said engaging means may be arranged to be deformed to engage the waveguide ends.

The said engaging means may be mounted on the said connector. In such a case, the said engaging means may comprise a pair of tubular projections which extend from opposite ends of the said longitudinal bore and which are axially aligned therewith.

Alternatively, the said engaging means may be of a heat-shrinkable material. In these circumstances, the engaging means may comprise two sleeves of heat-shrinkable material (for example, of plastics) which are to be heat-shrunk on to respective ends of the connector, the sleeves each having portions through which the ends of respective said waveguides are to extend and which are to be heat-shrunk on to those waveguide ends.

The ends of each of the flexible elongate members may be angularly displaced with respect to one another about the longitudinal axis of the said longitudinal bore. In such a case, the ends of each of the flexible elongate members may be displaced in the same sense about the longitudinal axis of the tubular body.

The ends of each of the flexible elongate members may be displaced by the same angular extent.

Various forms of optical waveguide couplings in accordance with the present invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a sectional side view of a connector of an optical waveguide coupling; Figure 2 is an end view of the connector of Figure 1; Figure 3 is a sectional side view of a modified form of the connector of Figures 1 and 2; Figures 4 and 5 are side views, partly in section, of one form of optical waveguide coupling in accordance with the present invention including the connector of Figures 1 and 2; and Figure 6 is a sectional side view showing an alternative form of optical waveguide coupling in accordance with the present invention including the connector of Figures 1 and 2.

The coupling includes a connector having a generally tubular body and a multiplicity of flexible elongate members extending through the tubular body and spaced apart around the body to define a longitudinal bore into opposite ends of which the ends of a pair of optical fibres are to be inserted. The diameter of the longitudinal bore defined by the flexible elongate members is arranged to be slightly less than the diameter of the optical fibres so that during insertion of the optical fibres into the longitudinal bore, the elongate members are deformed outwardly and resiliently engage the fibres to grip them and maintain them in axial alignment with one another.

Referring to Figures 1 and 2, the connector includes a tube 10 of a metal, such as brass or plastics, on which is mounted five wires 11 of resilient metal, such as, for example, stainless steel, copper alloy or phosphor bronze, that extend longitudinally through the bore of the tube 10 and are equally spaced around the tube. The wires 11 are tensioned with the ends of the wires being folded over the ends of the tube, and clamped to the tube 10 and maintained under tension, by rings 12 of, for example, brass or plastics. The wires 11 extend substantially in straight lines with the ends of each wire being angularly displaced with respect to one abother about the longitudinal axis of the tube 10 so that intermediate portions of the wires 11 are spaced from the inner surface of the tube 10. This angular displacement of the ends of the wires 11 is in the same sense for each wire 11 and is of the order of 1.5 degrees. The ends of the tube 10 are slotted to receive the wires 11. With such a connector the portions of the wires 11 within the tube 10 are slightly spaced from the tube, the degree of such displacement gradually increasing towards the centre of the tube 10 and thereafter gradually decreasing towards the other end of the tube 10.

Thus the bore defined in the tube 10 by the wires 11 is of smallest diameter at the centre of the tube. The bore diameter at the centre of the tube 10 is arranged to be slightly smaller than the diameter of optical fibres 13 (shown in dashed outline in Figure 1) inserted into the ends of the connector so that during such insertion of the fibre ends, the intermediate portions of the wires 11 are deformed outwardly towards the wall of the tube 10. The resilience of the wires 11 causes them to grip the ends of the fibres 13 and thereby automatically align them with one another and maintain them in axial alignment.

The ends of the fibres 13 are inserted into the connector one at a time, the end of the first fibre being pushed completely through the tube 10, cleaned to remove any dirt and then withdrawn into the tube until the fibre end is disposed in the centre of the tube. The end of the other fibre 13 is then cleaned and inserted into the tube 10 until it firmly abuts, and is thus spliced to, the other fibre end.

One or both of the fibre ends, before being inserted into the connector, may be coated with a fluid having the desired optical characteristics to maximise the optical coupling between the fibres. This fluid may be one having adhesive properties so as additional to join together the fibre ends. In addition, or alternatively, the space between the tube 10 and the fibre ends may be filled with an epoxy adhesive to anchor the fibre ends in the tube.

Such an optical waveguide coupling is described and claimed in our co-pending Patent Application No. 11021/76 (serial no.

15725015.

The fibre 13 may comprise single fibres or bundles of fibres.

In order to assist insertion of these fibres, and especially single fibres, into the tube 10, the tube may carry end pieces having tapered holes to receive the fibre ends. Such a coupling device is shown in Figure 3 where the rings 12 are replaced by end pieces 14 of metal or plastics having annular portions 15 which clamp the ends of the wires 11 to the tube 10, and end portions 16 which project from the ends of the tube 10 and have tapered holes 17 therein to receive the fibre ends.

It is necessary to grip the ends of the fibres 13 firmly so as to maintain the splicing of the fibre ends and prevent withdrawal of the fibre ends from the connector. One form of coupling for this purpose in accordance with the present invention is shown in Figures 4 and 5 where the connector is disposed within a sleeve 18 of heat-shrinkable plastics shaped, as shown in Figure 4, to provide tapered apertures 19 to receive the fibre ends. When the sleeve 18 is heated it shrinks as shown in Figure 5 to grip the connector and the fibre ends to prevent relative movement of those parts and thereby prevent removal of the fibre ends from the connector.

The sleeve 18 is in two parts which are slid ably mounted on respective one of the fibre ends before those ends are inserted into the connector. One of the fibre ends is then inserted into the connector and the respective sleeve part 18 heat shrunk on to that fibre end and the adjacent end of the connector, before the other fibre end is inserted into the connector and the other sleeve part 18 heat shrunk on to that fibre end and the other end of the connector.

An alternative form of coupling in accordance with the present invention is shown in Figure 6 where the rings 12 are replaced by end pieces 20 of a deformable metal or plastics having annular portions 21 which clamp the ends of the wires 11 to the tube 10 and end portions 22 which project from the ends of the tube and define sleeves to receive the optical fibres 13. When the ends of the fibres 13 have been inserted into the connector and spliced to one another, the sleeves 22 are crimped to grip the fibres 13 and prevent their withdrawal from the connector.

Various other arrangements may be provided to inhibit withdrawal of the fibre ends.

For example, the rings 12 of Figures 1 and 2 may carry respective end pieces (not shown) which are externally-threaded and have pairs of diametrically-opposed projections whose free ends are spaced to define a gap through which the respective fibre ends are inserted into the connector. The end pieces carry nuts which when screwed on to the end pieces engage the respective pairs of projections to urge their free ends into engagement with the fibre ends to grip them tightly and prevent the fibres being withdrawn from the connector.

It is visualised that the couplings may be for optical waveguides other than optical fibres.

WHAT WE CLAIM IS: 1. An optical waveguide coupling having a connector defining a longitudinal bore which is arranged to receive the ends of a pair of optical waveguides and to align those waveguide ends with one another, wherein the connector comprises a support member and a multiplicity of flexible elongate members mounted on the support member and defining the said longitudinal bore, the elongate members being spaced apart about the axis of the longitudinal bore and being individually deformable in an outwards direction, and wherein the coupling comprises means for engaging the ends of a pair of optical waveguides inserted in the longitudinal bore to anchor the waveguide ends in the connector.

2. An optical waveguide coupling according to Claim 1, wherein the said engaging means is arranged to be deformed to engage the waveguide ends.

3. An optical waveguide coupling according to Claim 1 or Claim 2, wherein the said engaging means is mounted on the said connector.

4. An optical waveguide coupling according to Claim 3, wherein the said engaging means comprises a pair of tubular proj ections which extend from opposite ends of the said longitudinal bore and which are axially aligned therewith.

5. An optical waveguide coupling according to Claim 4, wherein the tubular projections are of metal.

6. An optical waveguide coupling according to Claim 1 or Claim 2, wherein the said engaging means is of a heat-shrinkable material.

7. An optical waveguide coupling according to Claim 6, wherein the said engaging means comprises two sleeves of heatshrinkable material which are to be heatshrunk on to respective ends of the connector, the sleeves each having portions through which the ends of respective said waveguides are to extend and which are to be heatshrunk on to those waveguide ends.

8. An optical waveguide coupling according to Claim 6 or Claim 7, wherein the said engaging means is of plastics.

9. An optical waveguide coupling according to any one of the preceding claims, wherein the said support member is a tubular member.

10. An optical waveguide coupling according to any one of the preceding claims, wherein the ends of each of the flexible elongate members are angularly displaced with respect to one another about the longitudinal axis of the said longitudinal bore.

11. An optical waveguide coupling according to Claim 10 wherein the ends of each of the flexible elongate members are displaced in the same sense about the longitudinal axis of the tubular body.

12. An optical waveguide coupling according to Claim 11, wherein the ends of each of the flexible elongate members are displaced by the same angular extent.

13. An optical waveguide coupling according to any one of the preceding claims, wherein the flexible elongate members are of circular cross-section.

14. An optical waveguide coupling according to any one of the preceding claims, wherein the flexible elongate members are of metal.

15. An optical waveguide coupling according to any one of the preceding claims, wherein the flexible elongate members are of stainless steel.

16. An optical waveguide coupling according to any one of Claims 1 to 14, wherein the flexible elongate members are of copper alloy.

17. An optical waveguide coupling according to any one of Claims 1 to 14, wherein the flexible elongate members are of

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. ably mounted on respective one of the fibre ends before those ends are inserted into the connector. One of the fibre ends is then inserted into the connector and the respective sleeve part 18 heat shrunk on to that fibre end and the adjacent end of the connector, before the other fibre end is inserted into the connector and the other sleeve part 18 heat shrunk on to that fibre end and the other end of the connector. An alternative form of coupling in accordance with the present invention is shown in Figure 6 where the rings 12 are replaced by end pieces 20 of a deformable metal or plastics having annular portions 21 which clamp the ends of the wires 11 to the tube 10 and end portions 22 which project from the ends of the tube and define sleeves to receive the optical fibres 13. When the ends of the fibres 13 have been inserted into the connector and spliced to one another, the sleeves 22 are crimped to grip the fibres 13 and prevent their withdrawal from the connector. Various other arrangements may be provided to inhibit withdrawal of the fibre ends. For example, the rings 12 of Figures 1 and 2 may carry respective end pieces (not shown) which are externally-threaded and have pairs of diametrically-opposed projections whose free ends are spaced to define a gap through which the respective fibre ends are inserted into the connector. The end pieces carry nuts which when screwed on to the end pieces engage the respective pairs of projections to urge their free ends into engagement with the fibre ends to grip them tightly and prevent the fibres being withdrawn from the connector. It is visualised that the couplings may be for optical waveguides other than optical fibres. WHAT WE CLAIM IS:

1. An optical waveguide coupling having a connector defining a longitudinal bore which is arranged to receive the ends of a pair of optical waveguides and to align those waveguide ends with one another, wherein the connector comprises a support member and a multiplicity of flexible elongate members mounted on the support member and defining the said longitudinal bore, the elongate members being spaced apart about the axis of the longitudinal bore and being individually deformable in an outwards direction, and wherein the coupling comprises means for engaging the ends of a pair of optical waveguides inserted in the longitudinal bore to anchor the waveguide ends in the connector.

phosphor bronze. r A 1