GB2048507A

GB2048507A - Optical fibre connectors

Info

Publication number: GB2048507A
Application number: GB7915244A
Authority: GB
Original assignee: Plessey Co Ltd
Current assignee: Plessey Co Ltd
Priority date: 1979-05-02
Filing date: 1979-05-02
Publication date: 1980-12-10
Also published as: GB2048507B

Abstract

A sphere lens 11 is accurately located relative to the end of an optical fibre 6 by arranging that the optical fibre is received by an interstice formed between three identical inter-engaging balls 8, 9, 10 located in the same plane at right-angles to the axis of the optical fibre and the sphere lens is seated in a recess presented by surfaces of the three balls on the side thereof remote from the side of entry of the optical fibre into said interstice, the end of said optical fibre preferably being bonded to the sphere lens. The balls may remain in situ or be removed. <IMAGE>

Description

SPECIFICATION Improvements relating to optical fibre connectors This invention relates to optical fibre connectors for interconnecting the ends of optical fibres and relates more specifically to such connectors of the kind forming the subject of our co-pending patent application No. 30197/77.

In co-pending patent application No. 30197/77 there is described an optical fibre connector comprising in respect of each of the optical fibres to be connected a connector body part formed at one end with a recess which accurately locates a sphere lens relative to an optical fibre receiving hole extending through said body part and terminating at the centre of said recess whereby the axis of the optical fibre received by said hole and preferably bonded to the surface of said sphere lens is aligned with the centre of the sphere lens, and in which connecting means is provided for connecting together in axial alignment two of said body parts with the sphere lenses of said parts arranged in opposed relationship.

In the above-numbered co-pending patent application the recess provided at one end of the connector body part accurately locates the sphere lens relative to the end of the optical fibre inserted through the fibre-receiving hole of the connector body part. The present invention has in view an alternative means for the positioning of the sphere lens relative to an associated optical fibre.

According to the present invention the sphere lens of an optical fibre connector of the general form described above is accurately located relative to the end of an optical fibre by arranging that the optical fibre is received by an interstice formed between three identical inter-engaging balls located in the same plane at right-angles to the axis of the optical fibre and the sphere lens is seated in a recess presented by surfaces of the three balls on the side thereof remote from the side of entry of the optical fibre into said interstice, the end of said optical fibre preferably being bonded to the sphere lens.

According to a preferred embodiment of the invention the three balls for locating the optical fibre are accommodated within a cylindrical recess formed at one end of a cylindrical connector body part which has extending axially therethrough a hole for receiving the optical fibre.

The optical fibre is preferably contained within a sleeve which is itself fitted into the connector body hole just above referred to.

The optical fibre may be bonded directly to the surface of the sphere lens which may itself be bonded to the recessed end of the connector body part by transparent cement, or the end of the optical fibre may be spaced. from the sphere lens surface by a short distance dependent upon the refractive index of the sphere lens material. In the latter case the intervening gap between the end of the optical fibre and the sphere lens may be filled with transparent bonding material that serves to bond the three optical fibre-locating balls to the connector body part.

In a further embodiment of the present invention it may be arranged that the three optical fibre-locating balls are removed from the connector part after locating the end of the optical fibre in its desired position relative to the sphere lens and the attachment of the fibre to the sphere lens. Such an arrangement could be provided by means of a releaseable or disconnectable ball restraining device which would allow the balls to be removed or withdrawn after use.

According to another feature of the present invention a sphere lens and associated optical fibre of a connector body part could be accurately located relative to one another by any other suitable means before the optical fibre end is fixed relative to the surface of the sphere lens.

By way of example one embodiment of the present invention will now be described with reference to the accompanying drawing which shows a diagrammatic part-sectional part elevational view of one of two co-operating parts of an optical fibre connector.

Referring to the drawing, the optical fibre connector part illustrated comprises a cylindrical ferrule 1 (e.g. brass) which is provided at one end with a cylindrical recess 2 having its base surface 3 perpendicular to the axis of the ferrule 1 and a hole 4 for receiving a sleeve 5 which holds a looseiy fitting optical fibre 6 substantially parallel to the ferrule axis. The left-hand end of the hole 4 is enlarged as shown to accommodate sheathing 7 of the optical fibre.

Prior to insertion of the optical fibre into the ferrule 1 three identical inter-engaging balls 8, 9 and 10 may be introduced into the cylindrical recess 1 which may be drilled slightly larger than the overall diameter of a circle embracing the three inter-engaging balls.

These balls 8,9 and 10 abut against the base surface 3 of the recess 2 and thus lie in a common plane at right-angles to the axis of the ferrule 1.The ball assembly is bonded to the ferrule 1 and presents an opening or interstice therethrough between the balls for receiving the end of an optical fibre. The ball assembly also provides a recess for seating a sphere lens 11 as shown which will be bonded to the end of the ferrule 1 so that the end of the optical fibre passing between the balls is accurately aligned with the centre of the sphere lens. The optical fibre 6 may contact the sphere lens 11 or be spaced from it according to the relative refractive indices of the optical fibre and sphere lens material.The sphere lens 11 may, for example, be composed of high refractive index glass, having a refractive index of between 1.9 and 2.1, but other suitable crystalline material for sphere lenses are calcium molybdate, yttium gallium garnet and gadolinium gallium garnet, the two latter materials having particularly good hardness charcteristics and being less susceptible than glass to moisture attack. In the case of synthetic sapphire, in which material precision spheres to an accuracy of one micron are already commercially availble for use as bearings, the refractive index of 1.78 will be too low for direct contact between the fibre end and the sphere lens 11 so it will be necessary for the fibre end to be spaced from the surface of the sphere lens by the inter-position of suitable transparent material. With a view to reducing reflection losses from the sphere lenses the outer surface of the lens may be coated with a thin film of anti-reflection composition.

As regards the fibre locating balls 8, 9 and 10, these may for example comprise commercially available sapphire, ruby or tungsten carbide balls, but balls of other material could alternatively be used. It will be appreciated from the foregoing description that the drawing shows one of two co-operating optical fibre connector body parts which will be brought together so that the sphere iends of one connector body will be in opposed relationship to the sphere lens of the co-operating connector body part, the two body parts conveniently being aligned by means of a sleeve which extends over the ferrules of the two connector parts.

Claims

1. A method of manufacturing an optical fibre connector part comprising an optical fibre and an associated sphere lens, in which the sphere lens is accurately located relative to one end of the optical fibre by arranging that the optical fibre is received by an interstice formed between three identical interengaging balls located in the same plane at rightangles to the axis of the optical fibre and the sphere lens is seated in a recess presented by surfaces of the three balls on the side thereof remote from the side of entry of the optical fibre into said interstice.

2. The method as claimed in claim 1, in which the end of the optical fibre is bonded to the sphere lens.

3. The method as claimed in claim 1 or claim 2, in which the three balls for locating the optical fibre are accommodated within a cylindrical recess formed at one end of a cylindrical body part which has extending radially therethrough a hole for receiving the optical fibre.

4. The method as claimed in claim 3, in which the optical fibre is contained within a sleeve which is itself fitted into the connector body hole.

5. The method as claimed in claim 1, in which after the location and fixing of the sphere lens relative to one end of the optical fibre the three balls are removed from the connector part.

6. An optical fibre connector having one or more parts constructed by the method of any one of the preceding claims.

7. An optical fibre connector as hereinbefore described with reference to the drawing.