Optical switch

1. An optical switch comprising:

a plurality of N input ports, N being greater than or equal to 3;

a plurality of M output ports, M being greater than or equal to 2; and

a plurality of displaceable beam steering arrangements which, during switching, displace, wherein said displaceable arrangements displace to and from positions of interception of substantially entire beams originating from said input ports and direct said beams on paths to said output ports; wherein each displaceable beam steering arrangement comprises a reflective arrangement which in a first mode of displacement, is retractable from the optical path of light exiting, in use, from a first input port; and, in a second mode of displacement, said reflective arrangement is displaceable into a position to receive light from a further input port without during its displacement interfering with other ports of said input ports located between said first port and said further port.

2. The switch according to claim 1 , wherein each reflective arrangement comprises a first reflective arrangement which intercepts a beam from an input port and directs the beam towards a second reflective arrangement which intercepts the beam exiting from the first reflective arrangement and directs the beam to an output port; wherein said first and second reflective arrangements are displaceable.

3. The switch according to claim 1 , wherein each reflective arrangement comprises a first reflective arrangement which intercepts a beam from an input port and directs the beam towards a second reflective arrangement which intercepts the beam exiting from the first reflective arrangement and directs the beam to an output port; wherein said first reflective arrangement is displaceable and said second reflective arrangement is fixed, during switching.

4. The switch according to claim 2 , wherein a plurality of pairs of first and second reflective arrangements are provided to direct a beam from a selected input port to a selected output port.

5. The switch according to claim 3 , wherein a plurality of pairs of first and second reflective arrangements are provided to direct a beam from a selected input port to a selected output port.

6. The switch according to claim 1 , wherein the input ports are spaced about an arc; each reflective arrangement being retractable substantially radially, in said first mode of displacement, and rotatable, in said second mode of displacement, between said first port and said further port.

7. The switch according to claim 1 , wherein each reflective arrangement is a periscope arrangement.

8. The switch according to claim 7 , wherein each reflective arrangement incorporates a periscope prism.

9. The switch according to claim 7 , wherein each reflective arrangement is mounted radially on a rotatable mount through a flexure; and the corresponding beam steering arrangement further comprises an actuator which causes said periscope arrangement to be radially displaceable against the resilience of said flexure.

10. The switch according to claim 8 , wherein each reflective arrangement is mounted radially on a rotatable mount through a flexure; and the corresponding beam steering arrangement further comprises an actuator which causes said periscope arrangement to be radially displaceable against the resilience of said flexure.

11. The switch according to claim 9 , wherein the actuator is an elongate piezo-electric actuator which is at one end secured to said mount and at its displaceable opposite end connected to said periscope arrangement by said flexure.

12. The switch according to claim 10 , wherein the actuator is an elongate piezo-electric actuator which is at one end secured to said mount and at its displaceable opposite end connected to said periscope arrangement by said flexure.

13. The switch according to claim 9 , wherein said periscope arrangement is equipped with a projection which is located between two abutments of said mount in order to limit the displacement of said periscope arrangement.

14. The switch according to claim 10 , wherein said periscope arrangement is equipped with a projection which is located between two abutments of said mount in order to limit the displacement of said periscope arrangement.

15. The switch according to claim 11 , wherein said periscope arrangement is equipped with a projection which is located between two abutments of said mount in order to limit the displacement of said periscope arrangement.

16. The switch according to claim 12 , wherein said periscope arrangement is equipped with a projection which is located between two abutments of said mount in order to limit the displacement of said periscope arrangement.

17. The switch according to claim 1 , wherein each reflective arrangement comprises:

a periscope arrangement with an upper reflective face, a lower reflective face and an intermediate reflector; and

an attached adjacent second periscope arrangement arranged to receive a beam reflected from said first periscope arrangement.

18. The switch according to claim 17 , wherein said intermediate reflector is a partial reflector.

19. The switch according to claim 7 , wherein the switch incorporates pairs of periscope arrangements; one of which is rotatable and the other one of which is fixed.

20. The switch according to claim 7 , wherein the switch incorporates pairs of periscope arrangements; both of which are independently rotatable.

21. The switch according to claim 1 , wherein said displaceable arrangements incorporate a first reflective arrangement with an upper and a lower reflective face which are separated by a first distance; and a second reflective arrangement with an upper and a lower reflective face which are separated by a second distance; the second distance being lower than the first distance.

22. The switch according to claim 1 , wherein the input and output ports are arranged as part of a plurality of arcs with at least one arc located within an outer arc.

23. The switch according to claim 1 , wherein an input port inward most extremity terminates in a first optical element which is fixed during switching and an output port inward most extremity terminates in a second optical element which is displaced by a beam steering arrangement.

24. The switch according to claim 1 , wherein a number of the input ports are configured to transmit across the switch to a number of the output ports.

25. An optical switch comprising:

a plurality of N input ports, N being greater than or equal to 3;

a plurality of M output ports, M being greater than or equal to 2; and

a plurality of displaceable beam steering arrangements which, during switching, displace, wherein said displaceable arrangements displace to and from positions of interception of substantially entire beams originating from said input ports and direct said beams on paths to said output ports; and

wherein each displaceable beam steering arrangement comprises a reflective arrangement comprising a periscope arrangement; said periscope arrangement being mounted radially on a rotatable mount through a flexure; and the corresponding beam steering arrangement further comprises an actuator which causes said periscope arrangement to be radially displaceable against the resilience of said flexure.

26. The switch according to claim 25 , wherein the actuator is an elongate piezo-electric actuator which is at one end secured to said mount and at its displaceable opposite end connected to said periscope arrangement by said flexure.

27. The switch according to claim 25 , wherein said periscope arrangement is equipped with a projection which is located between two abutments of said mount in order to limit the displacement of said periscope arrangement.

28. An optical switch comprising:

a plurality of N input ports, N being greater than or equal to 3;

a plurality of M output ports, M being greater than or equal to 2; and

a plurality of displaceable beam steering arrangements which, during switching, displace, wherein said displaceable arrangements displace to and from positions of interception of substantially entire beams originating from said input ports and direct said beams on paths to said output ports;

wherein the input and output ports are arranged as part of a plurality of arcs with at least one arc located within an outer arc.

29. The switch according to claim 23 , wherein the first and second optical elements each comprises a collimator.