GB2059621A

GB2059621A - Optical fibre connector

Info

Publication number: GB2059621A
Application number: GB7933138A
Authority: GB
Original assignee: Standard Telephone and Cables PLC
Current assignee: STC PLC
Priority date: 1979-09-25
Filing date: 1979-09-25
Publication date: 1981-04-23
Also published as: FR2466031A1; ES495318A0; FR2466031B1; JPS5695205A; ES8200484A1; GB2059621B; DE3035773A1

Abstract

A connector arrangement for an optical fibre 1 comprises an expanded beam termination 2 for the fibre and a reflection means 6, such as a prism, inclined at an angle to the optical axis of the termination 2. Typically the reflection means is one face of a prism, a second face of which is normal to the optical axis of the termination. If necessary a third face of the prism is treated to make it non-reflecting. When the prism is a so-called "roof" prism two such connectors may be used to make either a right-angled connection (Fig. 5a) or a substantially straight through connection (Fig. 5b). Other alternatives are described with reference to Figs. 7, 8 and 9 (not shown). <IMAGE>

Description

SPECIFICATION Optical fibre connector This invention relates to connectors for optical fibres.

It is sometimes necessary to make an optical fibre cable connection in a restricted space, either fibre-to-fibre or fibre-to-panel, and in corresponding situations in the electrical field this is commonly overcome by using right-angled connectors. In the case of optical fibre cable, right-angled bends in the cable are not obtainable. Optical fibre cables have only a limited bending capability and may even be restrained from too severe bending by a bend restrictor fitted over the end portion of the cable adjacent the connector (e.g. a socalled tapered "cow-tail"). In addition there may be a requirement for a length of "free" fibre within the connector to avoid strain.

It is clearly possible to make a right-angled connector by bringing the free fibre through a right-angle within the connector and this may be suitable when a butt joint is used. This technique is assumed to be obvious to those skilled in the art.

According to the present invention there is provided a connector arrangement for an optical fibre including an expanded beam optical termination the optical axis of which is coaxial with the axis of the fibre and flat reflection means adjacent and angled with respect to the optical axis of the termination.

Embodiments of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 illustrates the principle of a connector according to the invention, Figure 2 illustrates a connector with integral reflection means, Figure 3 illustrates a connector with a prism reflection means, Figure 4 illustrates a connector with a "roof" prism reflection means, Figures 5a and 5b illustrate applications of the connector of Fig. 4, Figure 6 illustrates another application of the connector of Fig. 4, Figure 7 illustrates a further form of connector with a prism reflection means, Figure 8 illustrates a form of connector with a lentiform termination in combinaton with a prism reflection means, and Figure 9 illustrates a connector with a lentiform relection means.

In the arrangement shown in Fig. 1 an optical fibre 1 is to be connected, via its expanded beam termination 2, with an optical device or another fibre termination 3 which may be, for example, mounted in a panel 4.

To allow for such a connection where space above the panel may be restricted, as by other equipment 5 the termination 2 is arranged with its optical axis at a right-angle with the axis of termination 3. A reflection surface 6 inclined at 45 to the axis of termination 2 effects the optical connection between termination 2 and 3.

In one embodiment of the invention the termination 2 and reflection surface 6 are integral, as shown in Fig. 2. The termination 2 in this case is formed from a graded index rod the end face of which is an optically flat surface 6 inclined at 45 to the optical axis. If the rod is of square section then light reflected from the inclined surface is transmitted through the flat lower side surface of the rod in the region x-x. If the rod is of round section then a flat surface can be formed in the region x-x.

As an alternative to forming the reflection surface integral with the beam expanding terminal 2 the reflection surface may be provided by a prism, as shown in Fig. 3. The prism 7 is a right angled prism and reflection occurs at the hypotenuse face of the prism.

The prism may be mounted close to or actually cemented to the end of the termination 2.

In the above and other embodiments to be described the necessary housing and attachment means for the connectors have been omitted from the drawings, these will be readily designed by those skilled in the art.

In the arrangement shown in Fig. 4 a socalled "roof" prism 8 is used, i.e. a rightangled prism in which the hypotenuse face is cemented to the end of the termination 2.

Normally total internal reflection occurs at both the other faces of such a prism. When used in the present circumstances however reflection is only allowed to occur at one of the faces 8a. The other face 8b is treated, as by the provision of an anti-reflection coating, to allow light reflected from the face 8a to pass freely therethrough. Two such connectors can be used to make a right-angled connection between two fibres, as shown in Fig. 5a, or a substantially straight connection, as shown in Fig. 5b.

Fig. 6 shows how connectors of the type shown in Fig. 4 can be used with modified connectors of the same type, in which both the right-angle faces have anti-reflection coatings, to provide optical couplers and splitters.

Only the prism elements are shown in Fig. 6.

Light entering prism 9 is split, part of the light being deflected through 90 and being emitted from prism 10, whilst the remainder passes straight through prism 11. Light entering prism 1 2 is similarly split, part of it being deflected through prism 11 and the rest passing straight through prism 1 0. By suitable positioning of the prisms relative to one another it is possible to control the ratios of reflected to unreflected light in the combination.

As an alternative to the use of right-angled triangular prisms, as described above, other shapes may be used. Fig. 7 shows the use of a right-angled trapezoid prism 1 3 with a reflection surface 14 inclined at 22.5 to the incident light. Two such prisms when placed together provide a double reflection with a total reflection angle of 45 . Other shapes will occur to those skilled in the art.

Fig. 8 shows the use of a triangular prism 1 5 in a connector in which the beam expander termination 16 is formed with a collimating lens structure 1 7. The termination and the prism are held in the proper positions relative to one another by suitable housing means etc.

not shown in the drawing.

Fig. 9 shows yet another embodiment in which the reflection surface is formed on the flat surface of a hemispherical lens 1 8 which is itself formed of two quarter-spheres 1 8a, 1 8b, each of which has one reflection surface and one (treated) non-reflection surface similar to the prism of Fig. 4. The spherical surface of each quarter sphere 1 Ba, 1 8b acts as a collimator for the attached termination 1 9a, 1 9b. Again, by suitable orientation of the two connectors either a right-angled or a straight connection may be effected.

Claims

1. A connector arrangement for an optical fibre including an expanded beam optical termination the optical axis of which is coaxial with the axis of the fibre and flat reflection means adjacent and angled with respect to the optical axis of the termination.

2. A connector arrangement according to claim 1 wherein the reflection means is angled at 45 with respect to the terminaton axis.

3. A connector arrangement according to claim 1 or 2 wherein the reflection means is an optical prism.

4. A connector arrangement according to claim 3 wherein the prism is attached to the end of the termination.

5. A connector arrangement according to claim 3 or 4 wherein the prism is an isosceles right-angle prism and the hypotenuse face forms the reflection means.

6. A connector arrangement according to claim 3 or 4 wherein the prism is an isosceles right-angle prism and the hypotenuse face is normal to the optical axis of the termination, one of the faces enclosing the right angle being treated so as to reduce or eliminate internal reflection thereat.

7. A connector arrangement according to claim 6 wherein the treated face is provided with a multilayer anti-reflection coating.

8. A connector arrangement for an optical fibre substantially as described with reference to any one of Figs. 2-9 of the accompanying drawings.