Synchronous optical network in frequency domain

• US 6,519,060 B1
• Filed: 06/04/1999
• Issued: 02/11/2003
• Est. Priority Date: 06/04/1999
• Status: Expired due to Fees

• Current Assignee: EZconn Corporation
• Original Assignee: Chorum Technologies, Inc.
• Inventors: Liu, Jian-Yu
• Primary Examiner(s): PASCAL, LESLIE C
• Application Number:
  US09/326,201
• Time in Patent Office: 1,348 Days
• Field of Search: 359/122, 359/124, 359/127, 359/130, 359/128
• US Class Current: 398/49
• CPC Class Codes: H04J 14/0206 Express channels arrangements
• CPC Class Codes: H04J 14/0208 Interleaved arrangements
• CPC Class Codes: H04J 14/0209 Multi-stage arrangements, e.g. by cascading multiplexers or demultiplexers
• CPC Class Codes: H04J 14/0212 using optical switches or wavelength selective switches [WSS]
• CPC Class Codes: H04J 14/0217 Multi-degree architectures, e.g. having a connection degree greater than two
• CPC Class Codes: H04Q 11/0005 Switch and router aspects
• CPC Class Codes: H04Q 11/0066 Provisions for optical burst or packet networks
• CPC Class Codes: H04Q 2011/0009 using wavelength filters
• CPC Class Codes: H04Q 2011/0016 using wavelength multiplexing or demultiplexing
• CPC Class Codes: H04Q 2011/0026 using free space propagation (e.g. lenses, mirrors)
• CPC Class Codes: H04Q 2011/0035 using miscellaneous components, e.g. circulator, polarisation, acousto/thermo optical
• CPC Class Codes: H04Q 2011/0039 Electrical control
• CPC Class Codes: H04Q 2011/0047 Broadcast; Multicast
• CPC Class Codes: H04Q 2011/0049 Crosstalk reduction; Noise; Power budget
• CPC Class Codes: H04Q 2011/0058 Crossbar; Matrix

Abstract

An optical wavelength add/drop multiplexer provides communications between two optical links supporting wavelength division multiplexing (WDM). A wavelength slicer spatially separates the input signal into two sets of channels. An optical filter, such as an interference filter, spatially separates the a subset of the input channels into an array of separated channels. A programmable optical add/drop switch array selectively routes channels from and array of input ports to an array of drop ports, substitutes channels from an array of add ports in place of the dropped channels, and routes the remaining input channels and added channels to an array of output ports. The channels from the output ports of the said add/drop switch array are then combined and transmitted into the second optical link. In an alternative embodiment, a circulated drop filter consisting of an optical circulator and a series of filter Bragg gratings is used to select a predetermined series of input channels to be processed by the add/drop switch array, with the remaining channels being passed by the circulated drop filter as express lanes.

Claims

1. In an optical communication system comprising a plurality of optical paths, a node coupled to at least one of the optical paths, the node comprising:

a demultiplexer operable to receive an input wavelength division multiplexed (WDM) signal and to separate the input WDM signal into at least a first subset of wavelength signals comprising a first plurality of wavelengths and a second subset of wavelength signals comprising a second plurality of wavelengths different from and interdigitally spaced among the first plurality of wavelengths, wherein the first and second pluralities of wavelength signals are processed differently depending on the wavelengths in each plurality of wavelength signals;

an express path operable to receive from the demultiplexer the first subset of wavelength signals, and to pass those wavelength signals from the node without further processing; and

a processing path operable to receive from the demultiplexer the second subset of wavelength signals such that those wavelength signals are processed within the node, wherein the processing path comprises an optical router operable to route at least some of the second subset of wavelength signals for receipt by another node in the communication system without converting the at least some of the second subset of wavelength signals to an electrical format.

2. The node of claim 1, wherein the processing path comprises an optical add/drop multiplexer comprising:

a plurality of input ports each operable to receive a wavelength signal from the second subset; and

a plurality of add ports each operable to receive one of a plurality of add signals;

wherein for each input port, the optical add/drop multiplexer is operable to selectively route either a wavelength signal or an add signal to a corresponding output port.

3. The node of claim 1, wherein the input WDM signal comprises a first input WDM signal and wherein the processing path comprises:

an optical cross connect operable to receive the second subset of wavelength signals of the first input WDM signal and to receive a third subset of wavelength signals of a second input WDM signal, the optical cross connect operable to selectively substitute a wavelength signal from the third subset for a wavelength signal of the second subset of wavelength signals.

4. The node of claim 3, wherein the wavelength signal from the third subset and the wavelength signal from the second subset comprise approximately the same wavelength.

5. The node of claim 3, wherein the first input WDM signal was receive by the node from a first optical path coupled to the node, and wherein the second input WDM signal was received by the node from a second optical path coupled to the node, wherein the optical cross connect is operable to interchange wavelength signals between the first and second paths coupled to the node.

6. The node of claim 1, wherein the processing path comprises a Synchronous Optical Network (SONET) router operable to electronically process and facilitate routing to other nodes in the communication system information carried by at least some of the second subset of wavelength signals.

7. The node of claim 1, further comprising a multiplexer operable to receive the second subset of wavelength signals from the processing path and to combine the second subset of wavelength signals with at least one other subset of wavelength signals to form an output WDM signal.

8. The node of claim 1, wherein the processing path comprises a protection path operable to facilitate routing at least some of the second subset of wavelength signals to another node in the communication system along a second communication path after detection of a fault along a first communication path between the node to the another node.

9. The node of claim 1, further comprising a multiplexer operable to receive the first subset of wavelength signals from the express path and to combine the first subset of wavelength signals with at least one other subset of wavelength signals to form an output WDM signal.

10. A method of optical communication, comprising:

separating a first input wavelength division multiplexed (WDM) signal received from a first optical path into a first plurality of subsets of wavelength signals;

separating a second input WDM signal received from a second optical path into a second plurality of subsets of wavelength signals;

interchanging wavelength signals between particular subsets of wavelength signals associated with the first and second input WDM signals such that at least one wavelength signal from a particular subset of the first input WDM signal is communicated to the second optical path and at least one wavelength signal from a particular subset of the second input WDM signal is communicated to the first optical path;

wherein the wavelength signals interchanged between the first and second optical paths comprise different wavelengths, and further comprising converting one of the interchanged wavelength signals to approximately match the wavelength of the signal being interchanged.

11. A node in an optical communication system, the node comprising:

a first demultiplexer operable to receive a first input wavelength division multiplexed (WDM) signal from a first optical path coupled to then ode and to separate the first input WDM signal into a plurality of subsets of wavelength signals;

a second demultiplexer operable to receive a second input WDM signal from a second optical path coupled to the node and to separate the second input WDM signal into a plurality of subsets of wavelength signals;

wherein at least one of the first and second input WDM signals comprises a first beam and a second beam, and wherein the demultiplexer receiving the at least one signal comprises;

an optical filter operable to decompose the second beam into a fifth beam and a sixth beam;

wherein the third beam and the fifth beam carry the first subset of wavelength signals and the fourth beam and the sixth beam carry the second subset of wavelength signals; and

wherein the third beam and the sixth beam have a first polarization and the fourth beam and the fifth beam have a second polarization that is transverse to the first polarization; and

an optical cross connect operable to receive only particular subsets of wavelength signals from the first and second input WDM signals, and to interchange wavelength signals between the particular subsets such that at least one wavelength signal from the particular subset of first input WDM signal is communicated to the second optical path and at least one wavelength signal from the particular subset of second input WDM signals is communicated to the first optical path.

12. The node of claim 11, wherein the demultiplexer further comprises a birefringent element that combines the third beam and the fifth beam to form a first demultiplexed signal comprising the first subset of wavelength signals and combines the fourth beam and the sixth beam to form a second demultiplexed signal comprising the second subset of wavelength signals.

13. The node of claim 11, wherein the wavelength signals interchanged between the first and second optical paths comprise approximately the same wavelength.

14. The node of claim 11, further comprising an optical add/drop multiplexer operable to substitute one of a plurality of add signals for a selected one of the wavelength signals from the subsets of input wavelength signals.

15. A method of communicating optical signals, comprising:

receiving an input wavelength division multiplexed (WDM) signal comprising a plurality of wavelength signals;

separating the input WDM signal into at least a first subset of wavelength signals comprising a first plurality of wavelengths and a second subset of wavelength signals comprising a second plurality of wavelengths different from and interdigitally spaced among the first plurality of wavelengths;

communicating the first subset of wavelength signals using an express path without further processing;

communicating the second subset of wavelength signals using a processing path; and

performing a signal processing function on at least a portion of the second subset of wavelength signals, wherein performing a signal processing function comprises routing at least some of the second subset of wavelength signals for receipt by another node in the system without converting the at least some of the wavelength signals to an electrical format.

16. The method of claim 15, wherein performing the signal processing function comprises:

receiving at each of a plurality of input ports at least one wavelength signal from the second subset of wavelength signals;

receiving at each of a plurality of add ports at least one of a plurality of add signals;

for each input port, communicating either one of the wavelength signals from the second subset of wavelength signals or one of the add signals to an output port associated with the input port.

17. The method of claim 16, further comprising cross connecting one of the wavelength signals from the second subset of wavelength signals received at a first input port to an output port associated with a second input port.

18. The method of claim 15, wherein the input WDM signal comprises a first input WDM signal and wherein performing a signal processing function comprises:

receiving a third subset of wavelength signals associated with a second input WDM signal; and

substituting a wavelength signal from the second subset of wavelength signals with a wavelength signal from the third subset of wavelength signals.

19. The method of the claim 18, wherein the wavelength signal from the third subset substituted for the wavelength signal from the second subset comprises approximately the same wavelength as the wavelength signal from the second subset.

20. The method of claim 15, wherein performing a signal processing function comprises routing at least some of the second subset of wavelength signals using a protection path.

21. The method of claim 15, further comprising combining wavelength signals communicated using the express path with other wavelength signals to form an output WDM signal.

22. The method of claim 15, further comprising combining wavelength signals communicated using the processing path with other wavelength signals to form an output WDM signal.

23. A method of optical communication, comprising:

receiving a first input wavelength division multiplexed (WDM) signal comprising a first beam and a second beam;

filtering the first input WDM signal using an optical filter operable to decompose the first beam into a third beam and a fourth beam and to decompose the second beam into a fifth beam and a sixth beam, wherein the third beam and the fifth beam carry a first subset of wavelength signals and the fourth beam and the sixth beam carry a second subset of wavelength signals, wherein the third beam and the sixth beam have a first polarization and the fourth beam and the fifth beam have a second polarization that is transverse to the first polarization;

separating a second input WDM signal received from a second optical path into a plurality of subsets of wavelength signals;

interchanging wavelength signals between particular subsets of wavelength signals associated with the first and second input WDM signals such that at least one wavelength signal from a particular subset of the first input WDM signal is communicated to the second optical path and at least one wavelength signal from a particular subset of the second input WDM signal is communicated to the first optical path.

24. The method of claim 23, wherein interchanging wavelength signals is performed by an optical cross-connect.

25. The method of claim 24, wherein:

the particular subsets of wavelength signals are predetermined; and

the optical cross connect only receives wavelength signals from the predetermined subsets of wavelength signals.

26. The method of claim 23, further comprising:

combining the third beam and the fifth beam to form a first demultiplexed signal comprising the first subset of wavelength signals; and

combining the fourth beam and the sixth beam to form a second demultiplexed signal comprising the second subset of wavelength signals.

27. The method of claim 23, wherein the wavelength signals interchanged between the first and second optical paths comprise approximately the same wavelength.

28. The method of claim 23, wherein the wavelength signals interchanged between the first and second optical paths comprise different wavelengths, and further comprising converting one of the interchanged wavelength signals to approximately match the wavelength of the other interchanged wavelength signal.

29. The method of claim 23, further comprising substituting one of a plurality of add signals for at least one wavelength signal associated with the first input WDM signal or the second input WDM signal.

30. In an optical communication system comprising a plurality of optical paths, a node coupled to at least one of the optical paths, the node comprising

a demultiplexer operable to receive a WDM signal comprising a first beam and a second beam, wherein the demultiplexer comprises:

an optical filter operable to decompose the first beam into a third beam and a fourth beam and to decompose the second beam into a fifth beam and a sixth beam;

wherein the third beam and the fifth beam carry the first subset of wavelength signals and the fourth beam and the sixth beam carry the second subset of wavelength signals, and wherein the first and second pluralities of wavelength signals are processed differently depending on the wavelengths in each plurality of wavelength signals; and

wherein the third beam and the sixth beam have a first polarization and the fourth beam and the fifth beam have a second polarization that is transverse to the first polarization;

an express path operable to receive from the demultiplexer the first subset of wavelength signals, and to pass those wavelength signals from the node without further processing; and

a processing path operable to receive from the demultiplexer the second subset of wavelength signals such that those wavelength signals are processed within the node.

31. The node of claim 30, wherein the demultiplexer further comprises a birefringent element that combines the third beam and the fifth beam to form a first demultiplexed signal comprising the first subset of wavelength signals and combines the fourth beam and the sixth beam to form a second demultiplexed signal comprising the second subset of wavelength signals.

32. The node of claim 30, wherein the processing path comprises an optical add/drop multiplexer comprising:

a plurality of input ports each operable to receive a wavelength signal from the second subset; and

a plurality of add ports each operable to receive one of a plurality of add signals;

wherein for each input port, the optical add/drop multiplexer is operable to selectively route either a wavelength signal or an add signal to a corresponding output port.

33. The node of claim 30, wherein the input WDM signal comprises a first input WDM signal and wherein the processing path comprises:

an optical cross connect operable to receive the second subset of wavelength signals of the first input WDM signal and to receive a third subset of wavelength signals of a second input WDM signal, the optical cross connect operable to selectively substitute a wavelength signal from the third subset for a wavelength signal of the second subset of wavelength signals.

34. The node of claim 33, wherein the wavelength signal from the third subset and the wavelength signal from the second subset comprise approximately the same wavelength.

35. The node of claim 33, wherein the wavelength signal from the third subset and the wavelength signal from the second subset comprise different wavelengths, and wherein the optical cross connect comprises a wavelength converter operable to convert the wavelength signal of the third subset to approximately match the wavelength of the wavelength signal of the second subset.

36. The node of claim 33, wherein the first input WDM signal was received by the node from a first optical path coupled to the node, and wherein the second input WDM signal was received by the node from a second optical path coupled to the node, wherein the optical cross connect is operable to interchange wavelength signals between the first and second paths coupled to the node.

37. The node of claim 30, wherein the processing path comprises a Synchronous Optical Network (SONET) router operable to electronically process and facilitate routing to other nodes in the communication system information carried by at least some of the second subset of wavelength signals.

38. The node of claim 30, wherein the processing path comprises an optical router operable to route at least some of the second subset of wavelength signals for receipt by another node in the communication system without converting the at least some of the second subset of wavelength signals to an electrical format.

39. The node of claim 30, further comprising a multiplexer operable to receive the second subset of wavelength signals from the processing path and to combine the second subset of wavelength signals with at least one other subset of wavelength signals to form an output WDM signal.

40. In an optical communication system comprising a plurality of optical paths, a node coupled to at least one of the optical paths, the node comprising:

a demultiplexer operable to receive a first input wavelength division multiplexed (WDM) signal and to separate the input WDM signal into at least a first subset of wavelength signals comprising a first plurality of wavelengths and a second subset of wavelength signals comprising a second plurality of wavelengths different from the first plurality of wavelengths, wherein the first and second pluralities of wavelength signals are processed differently depending on the wavelengths in each plurality of wavelength signals;

an express path operable to receive from the demultiplexer the first subset of wavelength signals, and to pass those wavelength signals from the node without further processing; and

an optical cross connect operable to receive the second subset of wavelength signals of the first input WDM signal and to receive a third subset of wavelength signals of a second input WDM signal, the optical cross connect operable to selectively substitute a wavelength signal from the third subset for a wavelength signal of the second subset of wavelength signals;

wherein the wavelength signal from the third subset and the wavelength signal from the second subset comprise different wavelengths, and wherein the optical cross connect comprises a wavelength converter operable to convert the wavelength signal of the third subset to approximately match the wavelength of the wavelength signal of the second subset.

41. The node of claim 40, wherein the input WDM signal comprises a first beam and a second beam, and wherein the demultiplexer comprises:

a wavelength filter having a polarization dependent optical transmission function such that the first beam is processed into a third beam and a fourth beam and the second beam is processed into a fifth beam and a sixth beam;

wherein the third beam and the fifth beam carry the first subset of wavelength signals and the fourth beam and the sixth beam carry the second subset of wavelength signals; and

wherein the third beam and the sixth beam have a first polarization and the fourth beam and the fifth beam have a second polarization that is transverse to the first polarization.

42. The node of claim 41, wherein the demultiplexer further comprises a birefringent element that combines the third beam and the fifth beam to form a first demultiplexed signal comprising the first subset of wavelength signals and combines the fourth beam and the sixth beam to form a second demultiplexed signal comprising the second subset of wavelength signals.

43. The node of claim 40, wherein the optical cross connect comprises a Synchronous Optical Network (SONET) cross connect operable to electronically process and facilitate routing to other nodes in the communication system information carried by at least some of the second subset of wavelength signals.

44. The node of claim 40, wherein the cross connect comprises an optical cross connect operable to route at least some of the second subset of wavelength signals for receipt by another node in the communication system without converting the at least some of the second subset of wavelength signals to an electrical format.

45. The node of claim 40, further comprising a multiplexer operable to receive at least a portion of the second subset of wavelength signals from the processing path and to combine the at least a portion of the second subset of wavelength signals with at least one other subset of wavelength signals to form an output WDM signal.

46. In an optical communication system comprising a plurality of optical paths, a node coupled to at least one of the optical paths, the node comprising:

a demultiplexer operable to receive an input wavelength division multiplexed (WDM) signal and to separate the input WDM signal into at least a first subset of wavelength signals comprising a first plurality of wavelengths and a second subset of wavelength signals comprising a second plurality of wavelengths different from the first plurality of wavelengths, wherein the first and second pluralities of wavelength signals are processed differently depending on the wavelengths in each plurality of wavelength signals;

an express path operable to receive from the demultiplexer the first subset of wavelength signals, and to pass those wavelength signals from the node without further processing; and

a processing path operable to receive from the demultiplexer the second subset of wavelength signals, the processing path comprising;

a protection path operable to facilitate routing at least some of the second subset of wavelength signals to another node in the communication system along a second communication path after detection of a fault along a first communication path between the node to the another node;

wherein the second subset of wavelength signals comprises a traffic subset and a protection subset, and wherein the node is operable to dynamically allocate wavelength signals between the traffic subset and the protection subset.

47. The node of claim 46, wherein the input WDM signal comprises a first beam and a second beam, and wherein the demultiplexer comprises:

a wavelength filter having a polarization dependent optical transmission function such that the first beam is processed into a third beam and a fourth beam and the second beam is processed into a fifth beam and a sixth beam;

wherein the third beam and the fifth beam carry the first subset of wavelength signals and the fourth beam and the sixth beam carry the second subset of wavelength signals; and

wherein the third beam and the sixth beam have a first polarization and the fourth beam and the fifth beam have a second polarization that is transverse to the first polarization.

48. The node of claim 47, wherein the demultiplexer further comprises a birefringent element that combines the third beam and the fifth beam to form a first demultiplexed signal comprising the first subset of wavelength signals and combines the fourth beam and the sixth beam to form a second demultiplexed signal comprising the second subset of wavelength signals.

49. The node of claim 46, wherein the processing path comprises an optical add/drop multiplexer comprising:

a plurality of input ports each operable to receive a wavelength signal from the second subset; and

a plurality of add ports each operable to receive one of a plurality of add signals;

wherein for each input port, the optical add/drop multiplexer is operable to selectively route either a wavelength signal or an add signal to a corresponding output port.

50. The node of claim 46, wherein the input WDM signal comprises a first input WDM signal and wherein the processing path comprises:

an optical cross connect operable to receive the second subset of wavelength signals of the first input WDM signal and to receive a third subset of wavelength signals of a second input WDM signal, the optical cross connect operable to selectively substitute a wavelength signal from the third subset for a wavelength signal of the second subset of wavelength signals.

51. The node of claim 50, wherein the wavelength signal from the third subset and the wavelength signal from the second subset comprise approximately the same wavelength.

52. The node of claim 51, wherein the wavelength signal from the third subset and the wavelength signal from the second subset comprise different wavelengths, and wherein the optical cross connect comprises a wavelength converter operable to convert the wavelength signal of the third subset to approximately match the wavelength of the wavelength signal of the second subset.

53. The node of claim 50, wherein the first input WDM signal was received by the node from a first optical path coupled to the node, and wherein the second input WDM signal was received by the node from a second optical path coupled to the node, wherein optical cross connect is operable to interchange wavelength signals between the first and second paths coupled to the node.

54. The node of claim 46, wherein the processing path comprises a Synchronous Optical Network (SONET) router operable to electronically process and facilitate routing to other nodes in the communication system information carried by at least some of the second subset of wavelength signals.

55. The node of claim 46, wherein the processing path comprises an optical router operable to route at least some of the second subset of wavelength signals for receipt by another node in the communication system without converting the at least some of the second subset of wavelength signals to an electrical format.

56. The node of claim 46, further comprising a multiplexer operable to receive at least a portion of the second subset of wavelength signals from the processing path and to combine the at least a portion of the of second subset of wavelength signals with at least one other subset of wavelength signals to form an output WDM signal.

57. A node in an optical communication system, the node comprising:

a first demultiplexer operable to receive a first input wavelength division multiplexed (WDM) signal from a first optical path coupled to the node and to separate the first input WDM signal into a plurality of subsets of wavelength signals;

a second demultiplexer operable to receive a second input WDM signal from a second optical path coupled to the node and to separate the second input WDM signal into a plurality of subsets of wavelength signals; and

an optical cross connect operable to receive only particular subsets of wavelength signals from the first and second input WDM signals, and to interchange wavelength signals between the particular subsets such that at least one wavelength signal from the particular subset of first input WDM signals is communicated to the second optical path and at least one wavelength signal from the particular subset of second input WDM signals is communicated to the first optical path;

wherein the wavelength signals interchanged between the first and second optical paths comprise different wavelengths, and wherein the optical cross connect comprises a wavelength converter operable to convert one of the interchanged wavelength signals to approximately match the wavelength of the other interchanged wavelength signal.

58. A method of communicating optical signals, comprising:

receiving an input wavelength division multiplexed (WDM) signal comprising a first beam and a second beam;

filtering the input WDM signal using an optical filter operable to decompose the first beam into a third beam and a fourth beam and to decompose the second beam into a fifth beam and a sixth beam, wherein the third beam and the fifth beam carry a first subset of wavelength signals and the fourth beam and the sixth beam carry a second subset of wavelength signals, and wherein the third beam and the sixth beam have a first polarization and the fourth beam and the fifth beam have a second polarization that is transverse to the first polarization;

communicating the first subset of wavelength signals using an express path without further processing;

communicating of the second subset of wavelength signals using a processing path; and

performing a signal processing function on at least a portion of the second subset of wavelength signals.

59. The method of claim 58, further comprising:

combining the third beam and the fifth beam to form a first demultiplexed signal comprising the first subset of wavelength signals; and

combining the fourth beam and the sixth beam to form a second demultiplexed signal comprising the second subset of wavelength signals.

60. The method of claim 58, wherein performing the signal processing function comprises:

receiving at each of a plurality of input ports at least one wavelength signal from the second subset of wavelength signals;

receiving at each of a plurality of add ports at least one of a plurality of add signals;

for each input port communicating either one of the wavelength signals from the second subset of wavelength signals or one of the add signals to an output port associated with the input port.

61. The method of claim 60, further comprising cross connecting one of the wavelength signals from the second subset of wavelength signals received at a first input port to an output port associated with a second input port.

62. The method of claim 58, wherein the input WDM signal comprises a first input WDM signal and wherein performing a signal processing function comprises:

receiving a third subset of wavelength signals associated with a second input WDM signal; and

substituting a wavelength signal from the second subset of wavelength signals with a wavelength signal from the third subset of wavelength signals.

63. The method of claim 62, wherein the wavelength signal from the third subset substituted for the wavelength signal from the second subset comprises approximately the same wavelength as the wavelength signal from the second subset.

64. The method of claim 62, wherein the wavelength signal from the third subset substituted for the wavelength signal from the second subset initially comprises a different wavelength from the wavelength signal from the second subset, and further comprising:

converting the wavelength of the wavelength signal from the third subset to at least approximately match the wavelength of the wavelength signal from the second subset.

65. The method of claim 62, wherein performing a signal processing function comprises routing at least some of the second subset of wavelength signals for receipt by another node in the system without converting the at least some of the wavelength signals to an electrical format.

66. The method of claim 62, wherein performing a signal processing function comprises routing at least some of the second subset of wavelength signals using a protection path.

67. The method of claim 62, further comprising combining wavelength signals communicated using the express path with other wavelength signals to form an output WDM signal.

68. The method of claim 62, further comprising combining wavelength signals communicated using the processing path with other wavelength signals to form an output WDM signal.

69. A method of communicating optical signals, comprising:

receiving a first input wavelength division multiplexed (WDM) signal comprising a plurality of wavelength signals;

separating the input WDM signal into at least a first subset of wavelength signals comprising a first plurality of wavelengths and a second subset of wavelength signals comprising a second plurality of wavelengths different from the first plurality of wavelengths;

communicating the first subset of wavelength signals using an express path without further processing;

receiving a third subset of wavelength signals associated with a second input WDM signal;

converting the wavelength of a wavelength signal from the third subset to at least approximately match a wavelength of a selected one of the wavelength signals from the second subset; and

substituting the converted wavelength signal from the subset of wavelength signals with the selected one of the wavelength signals from the second subset of wavelength signals.

70. A method of communicating optical signals, comprising:

receiving an input wavelength division multiplexed (WDM) signal comprising a plurality of wavelength signals;

separating the input WDM signal into at least a first subset of wavelength signals comprising a first plurality of wavelengths and a second subset of wavelength signals comprising a second plurality of wavelengths different from the first plurality of wavelengths, wherein the second subset of wavelength signals comprises a traffic subset and a protection subset;

communicating the first subset of wavelength signals using an express path without further processing;

communicating of the second subset of wavelength signals using a processing path; and

performing a signal processing function on at least a portion of the second subset of wavelength signals, the signal processing function comprising;

routing at least some of the second subset of wavelength signals to another node in the communication system along a second communication path after detection of a fault along a first communication path between the node to the another node; and

dynamically allocating wavelength signals between the traffic subset and the protection subset.

71. The method of claim 70, wherein separating the input WDM signal into at least a first subset of wavelength signals comprising a first plurality of wavelengths and a second subset of wavelength signals comprising a second plurality of wavelengths different from the first plurality of wavelengths comprises:

filtering the input WDM signal using an optical filter operable to decompose the first beam into a third beam and a fourth beam and to decompose the second beam into a fifth beam and a sixth beam, wherewith third beam and the fifth beam carry a first subset of wavelength signals and the fourth beam and the sixth beam carry a second subset of wavelength signals, and wherein the third beam and the sixth beam have a first polarization and the fourth beam and the fifth beam have a second polarization that is transverse to the first polarization.

72. The method of claim 71, further comprising:

combining the third beam and the fifth beam to form a first demultiplexed signal comprising the first subset of wavelength signals; and

combining the fourth beam and the sixth beam to form a second demultiplexed signal comprising the second subset of wavelength signals.

73. The method of claim 70, wherein performing the signal processing function comprises:

receiving at each of a plurality of input ports at least one wavelength signal from the second subset of wavelength signals;

receiving at each of a plurality of add ports at least one of a plurality of add signals;

for each input port, communicating either one of the wavelength signals from the second subset of wavelength signals or one of the add signals to an output port associated with the input port.

74. The method of claim 70, wherein performing the signal processing function comprises cross connecting one of the wavelength signals from the second subset of wavelength signals received at a first input port to an output port associated with a second input port.

75. The method of claim 70, wherein the input WDM signal comprises a first input WDM signal and wherein performing a signal processing function comprises:

receiving a third subset of wavelength signals associated with a second input WDM signal; and

substituting a wavelength signal from the second subset of wavelength signals with a wavelength signal from the third subset of wavelength signals.

76. The method of claim 75, wherein the wavelength signal from the third subset substituted for the wavelength signal from the second subset comprises approximately the same wavelength as the wavelength signal from the second subset.

77. The method of claim 70, wherein performing the signal processing function comprises:

receiving a first input wavelength division multiplexed (WDM) signal comprising a plurality of wavelength signals;

separating the input WDM signal into at least a first subset of wavelength signals comprising a first plurality of wavelengths and a second subset of wavelength signals comprising a second plurality of wavelengths different from the first plurality of wavelengths;

communicating the first subset of wavelength signals using an express path without further processing;

receiving a third subset of wavelength signals associated with a second input WDM signal;

converting the wavelength of a wavelength signal from the third subset to at least approximately match a wavelength of a selected one of the wavelength signals from the second subset; and

substituting the converted wavelength signal from the third subset of wavelength signals with the selected one of the wavelength signals from the second subset of wavelength signals.

78. The method of claim 70, wherein performing a signal processing function comprises routing at least some of the second subset of wavelength signals for receipt by another node in the system without converting the at least some of the wavelength signals to an electrical format.

79. The method of claim 70, further comprising combining wavelength signals communicated using the express path with other wavelength signals to form an output WDM signal.

80. The method of claim 70, further comprising combining wavelength signals communicated using the processing path with other wavelength signals to form an output WDM signal.