Variable-density optical cross-connect architectures and upgrades

1. An optical cross connect for receiving a plurality of input optical signals each having a plurality of spectral bands and transmitting a plurality of output optical signals each having one or more of the spectral bands, the optical cross connect comprising:

a concentrator disposed to redistribute the spectral bands included on the plurality of input optical signals among a plurality of first intermediate optical signals, each of the input optical signals having a plurality of the spectral bands;

a core cross connect disposed to redistribute the spectral bands included on the plurality of first intermediate optical signals among a plurality of second intermediate optical signals; and

an expander disposed to redistribute the spectral bands included on the plurality of second intermediate optical signals among the plurality of output optical signals,

wherein the first intermediate optical signals are less in number than the input optical signals and the second intermediate optical signals are less in number than the output optical signals.

2. The optical cross connect recited in claim 1 wherein the first intermediate optical signals and the second intermediate optical signals are equal in number.

3. The optical cross connect recited in claim 1 wherein the input optical signals and the output optical signals are equal in number.

4. The optical cross connect recited in claim 1 wherein the concentrator comprises a plurality of wavelength routing elements, each such wavelength routing element being adapted for selectively routing wavelength components between a first WRE optical signal and a plurality of second WRE optical signals according to a configurable state of such wavelength routing element.

5. The optical cross connect recited in claim 4 wherein the first WRE optical signal for each wavelength routing element corresponds to one of the first intermediate optical signals.

6. The optical cross connect recited in claim 4 wherein each of the second WRE optical signals for each wavelength routing element corresponds to one of the input optical signals.

7. The optical cross connect recited in claim 4 wherein the concentrator further comprises a protection fabric adapted to maintain redistribution of the spectral bands included on the input optical signals among the first intermediate optical signals in the event of a failure of one of the wavelength routing elements.

8. The optical cross connect recited in claim 1 wherein the expander comprises a plurality of wavelength routing elements, each such wavelength routing element being adapted for selectively routing wavelength components between a first WRE optical signal and a plurality of second WRE optical signals according to a configurable state of such wavelength routing element.

9. The optical cross connect recited in claim 8 wherein the first WRE optical signal for each wavelength routing element corresponds to one of the second intermediate optical signals.

10. The optical cross connect recited in claim 8 wherein each of the second WRE optical signals for each wavelength routing element corresponds to one of the output optical signals.

11. The optical cross connect recited in claim 8 wherein the expander further comprises a protection fabric adapted to maintain redistribution of the spectral bands included on the second intermediate optical signals among the output optical signals in the event of a failure of one of the wavelength routing elements.

12. The optical cross connect recited in claim 1 wherein the core cross connect comprises a plurality of wavelength routing elements, each such wavelength routing element being adapted for selectively routing wavelength components between a first WRE optical signal and a plurality of second WRE optical signals according to a configurable state of such wavelength routing element.

13. The optical cross connect recited in claim 12 wherein equivalents to each of the first intermediate optical signals are directed to each of the plurality of wavelength routing elements as the plurality of second WRE optical signals.

14. The optical cross connect recited in claim 13 wherein the first WRE optical signal for each of the plurality of wavelength routing elements corresponds to one of the second intermediate optical signals.

15. The optical cross connect recited in claim 12 wherein the core cross connect further comprises a protection fabric adapted to maintain redistribution of the spectral bands included on the first intermediate optical signals among the second intermediate optical signals in the event of a failure of one of the wavelength routing elements.

16. A method for distributing a plurality of spectral bands comprised by a plurality of input optical signals each having a plurality of the spectral bands onto a plurality of output optical signals, the method comprising:

redistributing the plurality of spectral bands included on the plurality of input optical signals onto a plurality of first intermediate optical signals, wherein each of the input optical signals has a plurality of the spectral bands;

redistributing the plurality of spectral bands included on the plurality of first intermediate optical signals onto a plurality of second intermediate optical signals; and

redistributing the plurality of spectral bands included on the plurality of second intermediate optical signals onto the plurality of output optical signals,

wherein the first intermediate optical signals are less in number than the input optical signals and the second intermediate optical signals are less in number than the output optical signals.

17. The method recited in claim 16 wherein the first intermediate optical signals and the second intermediate optical signals are equal in number.

18. The method recited in claim 16 wherein the input optical signals and the output optical signals are equal in number.

19. The method recited in claim 16 wherein redistributing the plurality of spectral bands included on the plurality of input optical signals onto the plurality of first intermediate optical signals comprises, for each of a plurality of distinct groups of the input optical signals, propagating all of the spectral bands on the input optical signals within such distinct group onto a single first intermediate optical signal.

20. The method recited in claim 19 wherein each of the plurality of distinct groups of input optical signals comprises no more than two input optical signals.

21. The method recited in claim 19 wherein redistributing the plurality of spectral bands included on the plurality of input optical signals onto the plurality of first intermediate optical signals further comprises providing an equivalent to each of the plurality of input optical signals to a protection fabric.

22. The method recited in claim 16 wherein redistributing the plurality of spectral bands included on the plurality of second intermediate optical signals onto the plurality of output optical signals comprises, for each of a plurality of distinct groups of output optical signals, propagating all of the spectral bands onto the output optical signals within such distinct group from a single second intermediate optical signal.

23. The method recited in claim 22 wherein each of the plurality of distinct groups of output optical signals comprises no more than two output optical signals.

24. The method recited in claim 22 wherein redistributing the plurality of spectral bands included on the plurality of second intermediate optical signals onto the plurality of output optical signals further comprises providing an equivalent to each of the plurality of second intermediate optical signals to a protection fabric.

25. The method recited in claim 16 wherein redistributing the plurality of spectral bands included on the plurality of first intermediate optical signals onto the plurality of second intermediate optical signals comprises:

optically splitting each of the plurality of first intermediate optical signals into a plurality of equivalent optical signals;

receiving equivalent optical signals corresponding to each of the plurality of first intermediate optical signals at each of a plurality of working wavelength routing elements;

multiplexing selected spectral bands received on the equivalent optical signals with each of the plurality of working wavelength routing elements; and

transmitting respective second intermediate optical signals with the multiplexed spectral bands corresponding to the selection of each of the working wavelength routing elements.

26. The method recited in claim 25 wherein redistributing the plurality of spectral bands included on the plurality of first intermediate optical signals onto a plurality of second intermediate optical signals further comprises:

receiving equivalent optical signals corresponding to each of the plurality of first intermediate optical signals at least one protection wavelength routing element;

multiplexing selected spectral bands received on the equivalent optical signals with the at least one protection wavelength routing element to produce a protection signal; and

substituting the protection signal for one of the second intermediate optical signals to compensate for a fault.

27. The method recited in claim 16 further comprising increasing the number of first intermediate optical signals.

28. The method recited in claim 16 further comprising increasing the number of second intermediate optical signals.

29. The method recited in claim 16 further comprising increasing the number of input optical signals and increasing the number of output optical signals.

30. A method for upgrading a an optical cross connect comprising (1) a concentrator for redistributing spectral bands included on a plurality of input optical signals among a smaller number of first intermediate optical signals, (2) a core cross connect for redistributing spectral bands included on the first intermediate optical signals among second intermediate optical signals, and (3) an expander for redistributing spectral bands included on the second intermediate optical signals among a larger number of output optical signals, the method comprising:

upgrading a capacity of the core cross connect;

upgrading a capacity of at least one of the concentrator and expander; and

placing upgraded portions of the core cross connect and the at least one of the concentrator and expander in optical communication.

31. The method recited in claim 30 wherein upgrading a capacity of at least one of the concentrator and expander comprises adding an additional concentrator.

32. The method recited in claim 30 wherein upgrading a capacity of at least one of the concentrator and expander comprises adding an additional expander.

33. The method recited in claim 30 wherein:

the core cross connect comprises a working fabric having a plurality of optical components and a protection fabric configured to bypass at least one of the optical components in the event of a fault; and

upgrading the capacity of the core cross connect comprises:

upgrading a capacity of the protection fabric; and

sequentially, for each of the optical components,

bypassing spectral bands received by that optical component to the protection fabric;

thereafter, upgrading that optical component; and

thereafter, directing the bypassed spectral bands to that optical component.

34. The method recited in claim 30 wherein:

the concentrator comprises a working fabric having a plurality of optical components and a protection fabric configured to bypass at least one of the optical components in the event of a fault; and

upgrading the capacity of at least one of the concentrator and expander comprises upgrading the capacity of the concentrator by:

upgrading a capacity of the protection fabric; and

sequentially, for each of the optical components,

bypassing spectral bands received by that optical component to the protection fabric;

thereafter, upgrading that optical component; and

thereafter, directing the bypassed spectral bands to that optical component.

35. The method recited in claim 30 wherein:

the expander comprises a working fabric having a plurality of optical components and a protection fabric configured to bypass at least one of the optical components in the event of a fault; and

upgrading the capacity of at least one of the concentrator and expander comprises upgrading the capacity of the expander by:

upgrading a capacity of the protection fabric; and

sequentially, for each of the optical components,

bypassing spectral bands received by that optical component to the protection fabric;

thereafter, upgrading that optical component; and

thereafter, directing the bypassed spectral bands to that optical component.

36. A method for upgrading an optical cross connect comprising (1) a concentrator for redistributing spectral bands included on a plurality of input optical signals among a smaller number of first intermediate optical signals, (2) a core cross connect for redistributing spectral bands included on the first intermediate optical signals among second intermediate optical signals, and (3) an expander for redistributing spectral bands included on the second intermediate optical signals among a larger number of output optical signals, the method comprising:

adding a plurality of wavelength routing elements to the optical cross connect, each such wavelength routing element adapted for selectively routing wavelength components between a first WRE optical signal and a plurality of second WRE optical signals according to a configurable state of such wavelength routing element; and

bypassing spectral bands through at least some of the plurality of wavelength routing elements.

37. The method recited in claim 36 wherein:

bypassing spectral bands through at least some of the plurality of wavelength routing elements comprises bypassing the concentrator; and

the method further comprises removing the concentrator.

38. The method recited in claim 36 wherein:

bypassing spectral bands through at least some of the plurality of wavelength routing elements comprises bypassing the concentrator; and

the method further comprises reconfiguring the concentrator as one of the wavelength routing elements.

39. The method recited in claim 36 wherein:

bypassing spectral bands through at least some of the plurality of wavelength routing elements comprises bypassing the core cross connect; and

the method further comprises removing the core cross connect.

40. The method recited in claim 36 wherein:

bypassing spectral bands through at least some of the plurality of wavelength routing elements comprises bypassing the core cross connect; and

the method further comprises reconfiguring the core cross connect as one of the wavelength routing elements.

41. The method recited in claim 36 wherein:

bypassing spectral bands through at least some of the plurality of wavelength routing elements comprises bypassing the expander; and

the method further comprises removing the expander.

42. The method recited in claim 36 wherein:

bypassing spectral bands through at least some of the plurality of wavelength routing elements comprises bypassing the expander; and

the method further comprises reconfiguring the expander as one of the wavelength routing elements.

43. The method recited in claim 36 wherein one of the wavelength routing elements forms part of a protection fabric for the upgraded optical cross connect.

44. An optical cross connect for receiving a plurality of input optical signals each having a plurality of spectral bands and transmitting a plurality of output optical signals each having one or more of the spectral bands, the optical cross connect comprising:

means for redistributing the plurality of spectral bands included on the plurality of input optical signals onto a plurality of first intermediate optical signals, each of the input optical signals having a plurality of the spectral bands;

means for redistributing the plurality of spectral bands included on the plurality of first intermediate optical signals onto a plurality of second intermediate optical signals; and

means for redistributing the plurality of spectral bands included on the plurality of second intermediate optical signals onto the plurality of output optical signals,

wherein the first intermediate optical signals are less in number than the input optical signals and the second intermediate optical signals are less in number than the output optical signals.

45. The optical cross connect recited in claim 44 wherein the means for redistributing the plurality of spectral bands included on the plurality of input optical signals onto the plurality of first intermediate optical signals comprises means for propagating all of the spectral bands on the input optical signals within each of a plurality of distinct groups of the input optical signals onto a single first intermediate optical signal.

46. The optical cross connect recited in claim 44 wherein the means for redistributing the plurality of spectral bands included on the plurality of second intermediate optical signals onto the plurality of output optical signals comprises means for propagating all of the spectral bands on each single second intermediate optical signal onto output signals within one of a corresponding plurality of distinct groups of the output optical signals.

47. The optical cross connect recited in claim 44 wherein the means for redistributing the plurality of spectral bands included on the plurality of first intermediate optical signals onto the plurality of second intermediate optical signals comprises:

means for optically splitting each of the plurality of first intermediate optical signals into a plurality of equivalent optical signals;

means for receiving equivalent optical signals corresponding to each of the plurality of first intermediate optical signals at each of a plurality of working wavelength routing elements;

means for multiplexing selected spectral bands received on the equivalent optical signals with each of the plurality of working wavelength routing elements; and

means for transmitting respective second intermediate optical signals with the multiplexed spectral bands corresponding to the selection of each of the working wavelength routing elements.