GB2200764A

GB2200764A - N-way redundant optical fibre switch

Info

Publication number: GB2200764A
Application number: GB08702073A
Authority: GB
Inventors: Kevin John Warbrick
Original assignee: STC PLC
Current assignee: STC PLC
Priority date: 1987-01-30
Filing date: 1987-01-30
Publication date: 1988-08-10
Anticipated expiration: 2007-01-30
Also published as: GB8702073D0; GB2200764B

Abstract

Three or four fibres 5, 6, 7 and 8 are equally spaced around a standby fibre 9 in the fixed part of the switch, while in the moving part three or four movable fibres 10, 11, 12 and 13 are coupled directly to the fixed fibres. If any of the fixed fibres fails, the associated movable fibre is switched by pistons 15 into the gap between the other three so that it becomes optically coupled with the standby fibre 9. <IMAGE>

Description

N-WAY REDUNDANT OPTICAL FIBRE SWITCH This invention relates to optical fibre switches for providing redundancy in optical fibre systems.

Protection switching in optical transmission systems is becoming increasingly important. To achieve this electronically is expensive, and therefore there exists a need to do this optically in a relatively inexpensive way. One redundant channel servicing three or four operating channels are required configurations for protection switching in land line transmission systems.

According to the present invention there is provided an optical fibre switch in which a first set of (N+l) fibres, where N is three or four, comprising a central fibre with the other N fibres of the set equispaced around it, terminate in a common plane, and a second set of N fibres of the same size as those of the first set terminate in a second common plane adjacent with the first with ' the ends of the N fibres of the second set in optical registry with the ends of the N fibres of the second set that surround the central fibre, and where switching means are included adapted to move the end portion of any one of the fibres of the second set relative to the other (N-l) so as to rest between the other (N-l) so that it terminates in optical registry with the central fibre of the first set of fibres.

The switching means may conveniently be provided for instance by solenoid operated pistons or plungers by bimetallic strips or by piezoelectric elements.

There follows a description of two optical fibre switches embodying the invention in preferred forms. The description refers to the accompanying drawings in which: Figure 1 is a sectional schematic perspective view of one embodiment of switch with one portion reoriented so that both faces of the section are depicted; Figure 2 is a schematic transverse sectional view of the other embodiment of switch, and Figures 3 and 4 are schematic transverse sections of the embodiment of Figure 2 respectively in the unactuated state and in an actuated state.

Two vee-blocks 1,2 are fitted together to define an alignment guide or housing with a square aperture extending along its axis. The dimensions of this aperture are such that it just accommodates a first set of five fibres 5 to 9 which terminate in a common plane within the housing. Four of these fibres are fitted into the four corners of the square aperture, and between them define a space just large enough to accommodate the fifth in a central pOsition. A second set of fibres introduced into the opposite end of the housing also terminate in a common plane within the housing, this plane being adjacent the ends of the first set of fibres. This second set comprises only four fibres 10 to 13 which, in their relaxed state, rest against the four corners of the aperture.These four fibres are the same size as those of the first set of fibres, and hence any one of them is capable of being moved over from its corner position to lie in a central position rested between the other three.

In this position it will lie in line with the central fibre 9 of the first set. Actuating means are provided for effecting this movement. This may comprise four independent pistons 15 acting through four separate apertures 16. Conveniently these pistons are actuated by individual solenoids 17.

In normal use optical fibre 5 is coupled with fibre 10, fibre 6 with fibre 11, fibre 7 with fibre 12 and fibre 8 with fibre 13. In the event of a system malfunction involving any one of the four fibres 5 to 8, then fibre 9, the redundant or standby fibre, is activated and the corresponding fibre of the set of four fibres 10 to 13 is pushed across into the central position to couple witch this fibre.

One way by which the fibres 10 to 13 may conveniently be arranged to lie in their corner positions, when in the relaxed state, is by the use of a fifth fibre 14 (not shown in Figure 1) which is a dummy fibre that terminates within the housing sufficiently well short of the pistons to permit appropriate flexing of any one of the fibres when its piston is activated.

In an alternative form of switch depicted in Figures 2, 3 and 4 the four solenoid operated pistons 15 of Figure 1 that ac-t through apertures 16 in the housing directly upon the fibres 10 to 13 are replaced with pistons 25 that.act instead upon the walls of a flexible housing 26. The housing in this instance is designed with a cruciform cross section aperture to accommodate the fibres. Alternatively it could have had the same cross-section as the housing of Figure 1. When none of the pistons is activated the housing is straight, and in consequence the four fibres 10 to 13 lie in the arms of the cross, and hence are optically coupled with fibres 5 to 8 respectively as depicted in Figure 3. When however, by operation of one of the pistons, a bend is introduced into the middle section of the housing as depicted in Figure 4, the-stiffness of fibre 12 causes its end to move across the aperture into the central position where it is optically coupled with fibre 9.

The foregoing specific description has related exclusively to switches in which one redundant channel services four operating channels, but it is to be understood that the invention is also applicable to switches in which the redundant channel services only three operating channels. In this case the equispacing of the fibres provides for the first set of fibres three fibres spaced at 1200 around the central fibre instead of four spaced at 900.

Claims

CLAIMS:-

1. An optical fibre switch in which a first set of (N+l) fibres, where N is three or four, comprising a central fibre with the other N fibres of the set equispaced around it, terminate in a common plane, and a second set of N fibres of the same size as those of the first set terminate in a second common plane adjacent with the first with the ends of the N fibres of the second set in optical registry with the ends of the N fibres of the second set that surround the central fibre, and where switching means are included adapted to move the end portion of any one of the fibres of the second set relative to the other (N-l) so as to rest between the other (N-l) so that it terminates in optical registry with the central fibre of the first set of fibres.

2. An optical switch as claimed in claim 1 wherein the ends of both sets of fibres are accommodated in an alignment member and the actuating means includes pistons operable on individual fibres through apertures provided in the walls of the actuating member.

3. An optical fibre switch as claimed in claim 1 wherein the ends of both sets of fibres are accommodated in a flexible alignment member, and the actuating means is operable upon the alignment member to bend it.

4. An optical fibre switch in which the first set of fibres consists of five fibres.

5. An optical fibre switch substantially as hereinbefore described with reference to Figure 1 or Figures 2, 3 and 4 of the accompanying drawings.