OPTICAL FIBER SWITCH

Abstract: An optical fiber relay for switching optical signals between different signal paths contains a fixed first holder (12) with optical fibers (13, 14, 15) arranged in parallel, and a movable slide (8) similarly with optical fibers (19, 20, 21) arranged in parallel. For switching, the slide (8) can be displaced with the aid of a rigidly clamped leaf spring (26). In accordance with the invention, indirect actuation of the movable slide (8) takes place via a counteracting leaf spring (27). An armature bracket (29) is mounted on the armature (24) and has a tongue (32) engaging against the counteracting spring (27). When the relay is put in the make state, the tongue (32) urges the counteracting spring (27) downwards so that the counteracting spring bias is inhibited, whereby the rigidly clamped spring (26) displaces the slide (8).

Description: OPTICAL FIBRE SWITCH TECHNICAL FIELD The present invention relates to an optical fibre switch containing optical fibre conductors for switching optical signals through a first plurality of fibres disposed in parallel to a second plurality of fibres disposed in parallel. Such a switch may be used as a relay e.g. for a loop system in the connection point between the fibre loop and the bus terminal. BACKGROUND ART In the optical fibre switch described in the Swedish patent appli¬ cation 8204085.8 there is included a movable slide to which the optical fibres are attached. The fibres run along parallel to a fixed holder in the switch. Fibre ends having the same properties and dimensions as those in the movable slide are fixedly arranged at the switching point. The movable slide is actuated by the movable armature in an electromagnetic iron circuit for providing the switching action, and the movable slide is returned to its neutral position in an unactuatεd state with the aid of a return spring. DISCLOSURE OF INVENTION In the known switch, direct actuation of the movable slide is achieved by an actuation arm provided with a spring tongue moving the slide under the action of a magnetic force from one position to the other. In practice there are problems with this direct actuation, however, since the tongue of the actuating arm should be stiff at the beginning of the movement but weak at the end of it to withstand pressure without the action of an unnecessarily large magnetic force. The object of the present invention is to solve the above-mentioned problem by providing an actuation means in an optical fibre relay which has an indirect action on the movable slide. The invention is thereby characterized as disclosed in the characterizing portion of claim 1. OMH BRIEF DESCRIPTION OF DRAWINGS The invention will now be described in detail with reference to the accom¬ panying drawings, on which Figure 1 is a total view of an optical fibre switch in accordance with the above mentioned Swedish patent application. Figure 2 is a schematic diagram of fibres and the movement of the slide Figure 3 is a schematic diagram of the slide movement Figure 4 is a total view of a switch with indirect actuation in accordance with the present invention Figure 5 is a detail view of a switch with indirect actuation according to Figure 4, and Figure 6 is a side view of the same swith. BEST MODES FOR CARRYING OUT THE INVENTION A general view is illustrated in Figure 1 of the optical fibre switch according to the above mentioned Swedish patent application, in the form of a relay. The relay is constructed on a bottom plate 1 along the long side of which two iron cores 2 and 3 are attached. An armature 4 of soft, magnetic material is attached to an armature spring 5. The flux is generated in a manner known per se, with the aid of an unϊllustrated coil which magnetizes an iron circuit in which the magnetic cores 2, 3 and the armature 4 are included. A holder 12 is attached to the bottom plate. The holder fixes three optical fibres 13, 14 and 15. A movable slide 8 can glide in a movement substantially perpendicularly to the longitudinal direction of the fibres 13, 14, 15. Three optical fibres 19, 20 and 22 are fixed to the slide 8. These fibres extend to the right in the figure, past the right end edge of the slide, and are anchored in a fixed holder 16. A return spring 17 keeps the movable slide 8 in place in its starting position where the slide is pressed against the core 2. On magnetizing, the movable slide is moved into engagement against the guide plate 10 at the surface denoted by the numeral 11 in the figure. In the described relay, as well as in similar structures for optical fibre switching, it is normal that the armature directly actuates the movable slide. When the armature 4, on operation, moves towards the core 2, the spring tongue 7 will approach the movable slide 8 and when the tongue meets the slide the former will first flex a given distance in response to the inertia of the slide 8 and the spring bias in the return spring 7, and will subsequently begin to push the movable slide 8 until the latter is stopped by the surface 11. When the armature 4 then continues its movement into full engagement against the core 2, the spring tongue 7 is forced to deflect further. In an optical fibre relay for switching, the movement of the fibre carrying slide will be determined by the spacing between the fibres. For a known relay according to the above, Figure 2 illustrates the spacing D and the distance E which the movable slide moves when the relay is operated, and the distance E must in principle be equal to D in order that the centre lines of the fibres will coincide before and after the movement. Figure 3 schematically illustrates the distance E and the distance the armature suitably moves, namely H, which is equal to E + F + G, where the additional distance F may designate play or lost motion in the armature before the movable slide is actuated. The distance F may be said to be necessary to allow armature bounce when the relay is released without the slide giving the optical connection being affected. The distance G is the play or lost motion of the armature in the make state which ensures that minor dimensional inaccuracies do not affect the optical connection. The distances G and F contribute to the reliable function of the relay, and in practice they are small in relation to the necessary movement E. Some form of spring means must be applied to provide the lost motions corresponding to distances G and F for a directly actuating armature. In Figure 1, this spring means is the spring tongue 7. In a practical embodiment there is an opposed relationship, however, since the tongue 7 should be stiff at the beginning of the movement so that the lost motion corresponding to F will not be large and thus require a large armature stroke. On the other hand, at the termination of stroke .the liftning tongue should be weak, so as to withstand pressure without the force increasing too much. The present invention has been brought about to solve this problem. An indirect operating optical fibre switch in accordance with the invention is ΪFI illustrated in figures 4, 5 and 6. A make spring 26 attached to a core 23 is biassed so that it gives the movable slide 28, corresponding to the slide 8 in the known relay, a force P, in the order of magnitude 150 mN. A break spring 28 attached to a guide plate 40 is biassed so that it gives the movable slide 28 a force P in the order of magnitude 300 mN. The resultant P 2 - P-, will be about 150 mN and constitutes the force which in a release state keeps the movable slide 28 against a core 22 corresponding to the core 2 in Figure 1. The complete appearance of an armature bracket 29 is illustrated in figures 5 and 6, this only being partially apparent from Figure 4. In Figure 5, the armature 24 is provided with the armature bracket 29 which upon the make action via the adjustable tongue 32 influences the break spring 27 thus moving this downwards. Thereby the make spring 26 can influence the movable slide 28 so that it executes its movement and reaches its stop against the arresting surface 31 of the guide plate 30. The make spring 26 keeps the movable slide 28 pressed against the stop surface 31. The armature 24 can continue its movement until it is arrested by the pole boss 35. The forces acting on the armature in this indirectly driven coupling in the make state are: during the first part distance F (see Figure 3), only the counter directed force (about lOQmN) of the armature spring 25. During the next distance E, the break state spring 27 (about 300 mN) also acts on the armature counter to the direction of movement, and the make state, spring 26 (about 150 mN) acts on the armature with the direction of movement, which means that the armature during this distance shall overcome a force of about 100 + 300-150 = 250 mN. When the movable slide has been arrested against the stop surface 31, there remains the part distance G of the armature movement. During this part G the armature is influenced by the armature spring 25 plus the break state spring 27, i.e. about 100 + 300 = 400 N. The construction of the inventive relay is not limited to a leaf spring 26 being used as a make spring for the fibres. It is also possible to pretension the fibres 19, 20, 21 at the holder 36 so that a biassing spring force occurs in the fibres themselves. The spring 27 will then act with a counter force on one or all of the fibres 19, 20, 21. By the indirect action on the movable slide described here the following advantages are afforded: - The slide 28 is acted on by the make state spring 26 immediately when the armature tongue actuates the break state spring 27 since the armature bracket tongue 32 is stiff. This means that the lost motion F can be made short. - The lost motion F can be adjusted by bending the tongue 32. - During the armature distance G the force which is to be overcome is only that of the return force in the armature spring 25 and the release state spring 27. - The lost motion G is adjusted by bending the armature bracket tongue 33. - The armature stroke can be made less with this indirectly driven coupler than with a direct driven coupler, which requires a resilient armature tongue 7. - In the make state, the oscillating system (the slide 28 with its fibres and the operation state spring 27) is disengaged from the armature 24 with its relatively large mass, whereby the damping time for the vibrations occurring at the operation state will be shortened. In the manufacture of optical fibre relays according to the invention described here, the adjustment of the relay function data is facilitated in the following manner: The armature with mounted armature spring 25 can be checked for giving the proper force, and, if necessary, be adjusted before attaching to the core 23. The break state spring 26, which is mounted on the core 23, can be checked for the proper force and be adjusted, if necessary, before mounting of the slide 28 and the other guides associated with the fibres. The break state spring 27 which is mounted on its holder 40 can be checked for the right force and be adjusted, if necessary, before mounting the holder in the relay. The facility of separately adjusting the component springs 25, 26, 27 in the described manner results in that no operations are needed after the parts of the relay have been fitted in place and the risk of damaging the delicate fibre ends is thus considerably reduced. In respect of the armature 24, the method used for the springs has its counterpart in a measurement check and possible adjustment beforehand of the two adjusting tongues 32 and 33. In order that the movable slide 28 shall be guided by the bottom plate 27 in its movement, the fixed fibre holder 36 has been provided with two wire springs 37, 38 which give a force directed down O " ' PI " " towards the bottom plate 21 and which glide in grooves in the slide 28 when the slide 28 moves.

Claims: CLAIMS 1 An optical fibre switch for switching, i.e. closing, interrupting or changing an optical signal path, carried out with at least one fixedly arranged fibre end, which forms one signal path, and at least one movably arranged fibre end which forms the other signal path, magnetically activated actuation means being arranged for providing, in response to a magnetizing current, a displace¬ ment of the movable fibre end for coupling between the first and the second signal path, or for interrupting the signal path, characterized by a rigidly clamped first spring (21) for moving said fibre end (19, 20, 21), a second spring (27) counteracting the first spring, and means (29, 32) for inhibiting, on magnetic actuation, the counteraction of the second spring (27) so that under the action of the first spring the fibre end is moved to provide said switching or interruption. 2 Switch as claimed in claim 1, characterized in that said actuating means comprise a magnetically activable armature (24) and that said means comprise an armature bracket (29) provided with a tongue-like means (32) rigidly mounted on the armature, the tongue-like means inhibiting said counteraction on engagement against the other spring (27) on magnetic actuation, and during the movement of the armature. 3 Switch as claimed in claim 2, characterized in that the tongue-shaped means consists of an adjustable lifting tongue (32) for acting on the other spring (27). 4 Switch as claimed in claim 2, characterized in that the armature (24) has an adjustable tongue (33) for determining the stroke (H) of the armature. 5 Switch as claimed in claim 1, characterized in that one or both of the springs 26, 27 is a leaf spring. O..IPI

Inventors: THURENIUS AOKE GUNNAR HERBERT, THURENIUS, AOKE, GUNNAR, HERBERT
Applicants: ERICSSON TELEFON AB L M, TELEFONAKTIEBOLAGET L M ERICSSON
Application year: 1984
Main classification: G02B7
IPC codes: G02B6, G02B26