WO1994015232A1

WO1994015232A1 - Opctical connector

Info

Publication number: WO1994015232A1
Application number: PCT/GB1993/002655
Authority: WO
Inventors: Robert William Musk
Original assignee: Bt&D Technologies Limited
Priority date: 1992-12-28
Filing date: 1993-12-23
Publication date: 1994-07-07
Also published as: AU5819594A; JPH06230244A

Abstract

A PC connector is provided which prevents a plug (2) from being rotated relative to a receptacle (6) and can maintain an optimal positional relation between the forward ends of two fibre optic ferrules. The optical connector includes, in addition to the plug and the receptacle, a coil spring (8) anchored between the plug and the receptacle. The plug is latched to the receptacle in a predetermined rotation position. The spring (8) has one end portion (8a) extending along an axial direction of the plug and the other end portion (8b) extending in a direction perpendicular to that one end. Due to the engagement of the one end portion of the spring with an engaging groove (12) and engagement of that other end portion of the spring with a minor cutout (18c) of the receptacle, an urging rotation force of the spring acts only in one direction upon the plug so that the plug is maintained in a predetermined rotation position relative to the receptacle.

Description

OPTICAL CONNECTOR

The present invention relates to optical connectors and, in particular to so-called physical contact ("PC") connectors, that is optical connectors in which physical contact is made by the optical media which the connector connects. PC connectors have been developed so as to achieve low connection loss and high return loss. In the PC connector, the gap between two fibre optic ferrules is made sufficiently small compared with the working wavelength by arranging for the two ferrules to make physical contact near where the connected optical media, usually optical fibres, make optical contact. Conventionally, die ferrules for use in the PC connector have their forward ends finished by being polished into convex-spherical faces, and are so matched as to leave only a small gap, if any, between the convex-spherical faces of the two ferrules.

However, the standard PC connector has its ferrules rotated during assembly and so fails to maintain the relative optical position between those convex-spherical faces of the two ferrules. As a consequence, the connection loss often increases.

An angled PC connector has previously been proposed to solve the aforementioned problem. The angled PC connector includes a plug with a collar which has grooves formed in its outer peripheral surface, a receptacle that has rotation preventing projections engaging with the grooves of the collar, and a coil spring for urging the plug against the receptacle in an elastic fashion.

By bringing the rotation preventing projections of the receptacle into engagement with the grooves of the collar, it is possible to prevent the plug from being rotated and hence prevent the plug-mounted ferrules from being rotated.

In order to maintain the rotation preventing projections and grooves in an optimal positional relation through their proper engagement even if the plug and receptacle are repeatedly attached and detached, very tight manufacturing tolerances are required between the plug and the receptacle. In the existing angled PC connector, unless the aforementioned tight manufacturing tolerances are satisfied, connection losses constitute an unresolved problem. It is, accordingly, the object of the present invention to provide an optical connector which can solve the aforementioned problem inherent in the existing optical connectors. More specifically, it is an object of the present invention to provide an optical connector which can suppress the rotation of those fibre optic ferrules, without requiring particularly tight manufacturing tolerances between a plug and a receptacle, and achieve a decline in its connection loss.

According to the present invention, an optical connector is provided which connects the end face of a first fibre optic ferrule to the end face of a second fibre optic ferrule, the optical connector comprising: a plug having a collar section, into which the end face and adjoining portions of the first ferrule are inserted and a tubular section connected to the collar section and having a diameter smaller than that of the collar section, a hole being provided in the tubular section and collar section to guide the end face of the second ferrule to die end face of the first ferrule, wherein an engaging groove and rotation preventing grooves are provided in the outer peripheral surface of the collar section and extend along an axis of the first ferrule; a coil spring having first and second ends set in a direction substantially perpendicular to each other, the first end portion of the coil spring being engageable with the engaging groove of the collar section of the plug and the coil spring being loosely engageable around the tubular section of the plug; and a receptacle having one end portion holding the plug and the other end portion holding the second ferrule, a cutout being provided in the one end portion of the receptacle to latchingly hold the second end portion of the coil spring, projections being provided on its inner surface extending from the one end to that other hand of the receptacle so as to be latchingly engageable with the associated rotation preventing grooves, and the receptacle holding the second ferrule extending toward its one end from its other end wherein, when the projections of the receptacle are latched to the associated rotation preventing grooves of the plug, a force with which the plug is rotated about its axis acts, by the coil spring, in one direction only and, due to that force acting in a direction to urge the engagement of the projection with the rotation preventing groove, the first ferrule is held in a predetermined rotation position.

According to the optical connector of the present invention, the force with which the plug is rotated is biased toward one direction only, thus urging the engagement of the projection of the receptacle with the rotation preventing groove of the collar. By so doing it is possible to prevent the first ferrule which is mounted on the plug from being rotated.

The invention will now be described further by way of example with reference to the accompanying drawings of which: Fig. 1 is an exploded, perspective view showing an optical connector according to an embodiment of the present invention;

Fig.2 is a front view showing an inner structure of the receptacle;

Fig. 3 is a view, showing a state in which a plug and receptacle of the optical connector of Fig. 1 are latched to each other, and Fig.4 is a view showing a state in which, unlike the case of Fig. 3, no coil spring is used.

Referring to Fig. 1, an optical connector is shown which comprises a plug 2 into which an end face and neighbouring portions of a first fibre optic ferrule 4 is substantially coaxially inserted, a receptacle 6 associated with the plug 2, and a coil spring 8 provided between the plug and the receptacle. The optical connector is comprised of an angled physical contact ("PC") connector. Those facing end faces (not shown) of first and second fibre optic ferules 4a and 4b are each finished, by polishing, into a convex-spherical configuration.

The plug 2 is made of, for example, stainless steel and comprises a collar section 2 and a mbular section 2b connected to the collar section. A pair of rotation preventing grooves 10a, 10b and one engaging groove 12 are provided in the outer periphery of the collar section 2a along an axis of the plug 2. The rotation preventing grooves 10a and 10b are so located as to provide a rotation symmetry relative to the axis of the plug 2. A hole (not shown in Fig. 1) is formed in the collar section 2a and mbular section 2b along the axis of the plug 2. Through the hole, the end face of the second ferrule 4b is guided to the end face of the first ferrule 4a.

The receptacle 6 comprises a resin housing and has one end portion into which the plug 2 is fitted and the other end portion for holding a cable 14 with the second ferrule 4b contained therein. The second ferrule 4b extends from one end of the receptacle 6 and is inserted into the aforementioned hole of the mbular section 2b. As shown in Fig. 2, one pair of rotation preventing projections or positioning keys 16a, 16b are provided on an inner surface between one end and the other end of the receptacle 6 to engage with the rotation preventing grooves 10a and 10b.

Referring back to Fig. 1, the receptacle 6 has a pair of opposite cut-outs 18a, 18b extending from its one end into its substantially middle portion. One (18a) of these cut-outs merges into a minor cut-out 18c extending from the substantially middle portion toward that other end of the receptacle 6. The minor cut-out 18c of the receptacle 6 and engaging groove 12 of the plug 2 are positionally shifted around the axis of the ferrule 4 by an angle of 90^*. The coil spring 8 is loosely inserted around the mbular section 2b of the plug 2 and, together with the plug 2, inserted into the receptacle 6. A positioning peg 8a is provided at one end and a positioning peg 8b at the other end of the spring 8. The pegs 8a and 8b are positionally displaced at an angle of 90' relative to each other to have the same positional relationship as that between the minor cutout 18c and the engaging groove 12. The pegs 8a and 8b extend in a direction perpendicular to each other. Stated in more detail, the plug-side peg 8a extends along the engaging groove 12 of the plug 2 and the receptacle-side peg 8b extends from an inside toward an outside of the receptacle 6 so as to latchingly engage with the minor cutout 18c. With the optical connector in an assembled state, the rotation preventing grooves 10a and 10b of the plug 2 are latched to the rotation preventing projections 16a and 16b of the receptacle 6. At the same time, the pegs 8a and 8b are placed in latching engagement with the engaging groove 12 of the plug 2 and minor cutout 18c of the receptacle 6. As shown in Fig. 3, under an action of the spring 8, the key 16a of the receptacle 6 abuts against one wall face 20a defined in the groove 10a of the plug 2 and the key 16b of the receptacle 6 abuts against one wall surface 20b defined in the groove 10b of the plug 2. Since, in this case, the wall faces 20a and 20b of the grooves 10a and 10b have a rotational symmetry relative to the axis of the ferrule 4, the keys 16a and 16b of the receptacle 6 are urged into engagement with the grooves 10a and 10b of the plug 2, respectively. Fig. 3 shows the aforementioned hole 22 for holding the second fibre optic ferrule 4b.

To illustrate the action of the spring, it shall first be assumed for the sake of argument that no spring 8 isprovided for the plug 2 and receptacle 6. In this case, due to a limitation on the manufacturing tolerance of the plug 2 and/or receptacle 6, it is not sufficient to prevent the first ferrule 4a from being rotated simple through the engagement of the keys 16a and 16b with the grooves 10a and 10b. As shown in Fig.4, therefore, the ferrule 4a may be rotated in two directions.

However, in the presence of the sring 8, with the engagement of the plug 2 with the receptacle 6 by means of the spring 8, the ferrule 4a is positively prevented from being rotated because the rotation of the first ferrule 4a is biased to one direction only in which the latching engagement of the plug 2 is urged. Thus, an optimal positional relation can be maintained between the facing convex-spherical faces of the first and second ferrules 4a and 4b. The present invention is not restricted to the aforementioned embodiment only and various changes or modifications of the present invention can be made without departing from the spirit and scope of the present invention. For example, the angle at which the pegs 8a and 8b of the spring 8 are positioned is not restricted to 90^* only. The same applies to the angle at which the minor cutout 18c and engaging groove 12 are positioned. In either case, a proper acute or obtuse angle may be set within a range in which the proper engagement of the plug 2 and receptacle 6 are urged.

According to the optical connector of the present invention, as set out above, the plug and receptacle are urged by the coil spring into latching engagement with each other and it is thereby possible to prevent the ferrule from being rotated and hence to reduce connection losses.

Claims

1. An optical connector for connecting an end face of a first fibre optic ferrule to an end face of a second fibre optic ferrule, comprising: a plug having a collar section, into which the end face and neighbouring portions of the first ferrule are inserted, and a mbular section connected to the collar section and having a diameter smaller than that of the collar section, a hole being provided in the mbular section and collar section to guide the end face of the second ferrule to the end face of the first ferrule, wherein an engaging groove and rotation preventing grooves are provided in the outer peripheral surface of the collar section and extend along an axis of the first ferrule; biasing means having first and second end portions set in a direction substantially perpendicular to each other, the first end portion of the biasing means being engageable with the engaging groove of the collar section of the plug and the biasing means being loosely engageable around the mbular section of the plug; and a receptacle having one end portion holding the plug and the other end portion holding the second ferrule, a cutout being provided in the one end portion of die receptacle to latchingly hold the second end portion of the biasing means, projections being provided on its inner surface extending from the one end to the other end of the receptacle so as to be latchingly engageable with the associated rotation preventing grooves of the plug, and the receptacle holding the second f enrule extending toward its one end from its other end, wherein, when the projections of the receptacle are latched to the associated rotation preventing grooves of the plug, a force with which the plug is rotated about its axis acts, by the biasing means, in one direction only and, due to that force acting in a direction to urge the engagement of the projection with the rotation preventing groove, the first ferrule is held in a predetermined rotation position. An optical connector as claimed in claim 1 in which the biasing means comprise a coil spring having first and second ends set in a direction substantially perpendicular to each other.