Switch for optical signals

• US 6,606,427 B1
• Filed: 02/23/2000
• Issued: 08/12/2003
• Est. Priority Date: 10/06/1999
• Status: Expired due to Term

• Current Assignee: RPX Clearinghouse LLC (RPX Corporation)
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Spagnoletti, Robert William, Roorda, Peter, Baker, Nigel, Graves, Alan F.
• Primary Examiner(s): Healy, Brian
• Assistant Examiner(s): HAHM, SARAH UH YOUNG
• Application Number:
  US09/511,065
• Time in Patent Office: 1,266 Days
• Field of Search: 385/17,16,18,24 359/124,127,128
• US Class Current: 385/17
• CPC Class Codes: G02B 6/3512 the optical element being reflective, e.g. mirror
• CPC Class Codes: G02B 6/3546 NxM switch, i.e. a regular array of switches elements of matrix type constellation
• CPC Class Codes: G02B 6/356 in an optical cross-connect device, e.g. routing and switching aspects of interconnecting different paths propagating different wavelengths to (re)configure the various input and output links switching polarized beams G02B6/3594; power equalizers G02B6/356 and G02B6/3594; path selecting means H04Q11/0001
• CPC Class Codes: G02B 6/3849 using mechanical protective elements, e.g. caps, hoods, sealing membranes G02B6/3816 takes precedence; provisionally see H01R13/44
• CPC Class Codes: G02B 6/3885 Multicore or multichannel optical connectors, i.e. one single ferrule containing more than one fibre, e.g. ribbon type optical ribbon cable G02B6/4403, G02B6/448
• CPC Class Codes: G02B 6/3888 Protection from over-extension or over-compression
• CPC Class Codes: G02B 6/43 Arrangements comprising a plurality of opto-electronic elements and associated optical interconnections
• CPC Class Codes: H04Q 1/04 Frames or mounting racks for selector switches; Accessories therefor, e.g. frame cover
• CPC Class Codes: H04Q 11/0005 Switch and router aspects
• CPC Class Codes: H04Q 11/0071 Provisions for the electrical-optical layer interface
• CPC Class Codes: H04Q 2011/0011 using wavelength conversion
• 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 2201/804 in optical transmission systems

Abstract

A cross-connect switch for switching optical signals, in particular, Dense Wavelength Division Multiplexed (DWDM) signals is disclosed. The switch includes a switching matrix for each of the predetermined wavelengths of the DWDM signals. The switching matrices include Micro-Electro-Mechanical (MEM) systems which have optically reflective elements, typically mirrors, arranged in rows and columns for switching an incoming optical signal travelling along a row of such elements to an output port aligned with a column of the elements. The switch has input demultiplexers to split an incoming DWDM signal into its component channel wavelengths, each of which is directed to a switching matrix where it is switched to an output port and recombined into an outgoing DWDM signal by a multiplexer before being transmitted out of the switch. A wavelength-converting switch, connected across the switching matrices, is also included for switching channels between wavelengths.

Claims

1. An optical cross-connect switch, comprising:

a plurality of optical switching matrices, each switching matrix having multiple input ports, multiple output ports, at least one inter-matrix input port and at least one inter-matrix output port, each switching matrix being operable to switch an optical channel signal arriving on any input port to either any one of a plurality of the output ports or an inter-matrix output port, and being operable to switch an optical channel signal arriving on any inter-matrix input port to an output port, and each switching matrix being operable to switch optical channel signals having a respective distinct wavelength; and

a wavelength-converting inter-matrix switch connected between the inter-matrix output ports of the switching matrices and the inter-matrix input ports of the switching matrices, the wavelength-converting inter-matrix switch being operable to switch a signal arriving from any inter-matrix output port of any switching matrix to an inter-matrix input port of any of a plurality of the other switching matrices and being operable, in switching a first channel signal having a first wavelength from an inter-matrix output port of a first switching matrix to an inter-matrix input port of a second switching matrix, to convert the first channel signal having the first wavelength to a second channel signal having a second wavelength.

2. A cross-connect switch as defined in claim 1, wherein each switching matrix is operable to switch a signal arriving on any input port to any of the output ports.

3. A cross-connect switch as defined in claim 2, wherein each inter-matrix switch is operable to switch a signal arriving from any inter-matrix output port of any switching matrix to an inter-matrix input port of any of the other switching matrices.

4. A cross-connect switch as defined in claim 1, wherein:

each switching matrix has multiple inter-matrix output ports;

the wavelength-converting inter-matrix switch comprises multiple switching elements connected in parallel; and

each inter-matrix output port of a particular switching matrix is coupled to a respective one of the switching elements of the wavelength-converting inter-matrix switch.

5. A cross-connect switch as defined in claim 1, wherein:

the inter-matrix switch comprises at least one add input port and at least one drop output port;

the inter-matrix switch is operable to couple an add input signal arriving at the add input port to an inter-matrix input port of any switching matrix; and

the inter-matrix switch is operable to couple a signal arriving from an inter-matrix output port of any switching matrix to the drop output port.

6. A cross-connect switch as defined in claim 1, further comprising:

a plurality of wavelength division demultiplexers, each demultiplexer being operable to separate an optical input signal into a plurality of output channel signals having respective distinct wavelengths and to apply each output channel signal to a respective input port of a respective switching matrix such that each switching matrix receives only channel signals having a respective distinct wavelength;

a plurality of wavelength division multiplexers, each multiplexer having a plurality of inputs, each respective input of each multiplexer being coupled to an output port of a respective switching matrix to receive a respective channel signal having a respective wavelength, each multiplexer being operable to combine channel signals having distinct wavelengths into an optical output signal.

7. A cross-connect switch as defined in claim 1, wherein the wavelength-converting inter-matrix switch comprises:

multiple optical receivers coupled to inter-matrix output ports of the switching matrices, the optical receivers being operable to convert channel signals arriving from the inter-matrix output ports to electrical signals;

multiple optical transmitters coupled to the inter-matrix input ports of the switching matrices, the optical transmitters being operable to convert electrical signals to channel signals having predetermined wavelengths; and

an electrical switch connected between the optical receivers and the optical transmitters, the electrical switch being operable to switch an electrical signal from any optical receiver to any of a plurality of the optical transmitters.

8. A cross-connect switch as defined in claim 7, wherein the electrical switch is operable to switch an electrical signal from any optical receiver to any optical transmitter.

9. A cross-connect switch as defined in claim 1, wherein:

the wavelength-converting inter-matrix switch comprises an optical switch and a plurality of optical transponders connected to the switch;

each optical transponder is operable to convert a channel signal having a first wavelength into a channel signal having a second wavelength; and

the optical switch is operable to couple a channel signal arriving from an inter-matrix output port of any switching matrix to an inter-matrix input port of any of a plurality of other switching matrices via an optical transponder.

10. A cross-connect switch as defined in claim 9, wherein the optical switch is operable to couple a channel signal arriving from an inter-matrix output port of any switching matrix to an inter-matrix input port of any other switching matrix via a transponder.

11. A cross-connect switch as defined in claim 9, wherein the optical switch is coupled between the inter-matrix output ports and the optical transponders.

12. A cross-connect switch as defined in claim 9, wherein the optical switch comprises plural optical switching stages and the optical transponders are coupled between optical switching stages.

13. A cross-connect switch as defined in claim 12, wherein the optical switch comprises a multistage CLOS switch.

14. A cross-connect switch as defined in claim 9, wherein at least one optical transponder is a tunable optical transponder that is tunable to transmit channel signals of selectable distinct wavelengths.

15. A cross-connect switch as defined in claim 9, wherein at least one optical transponder is a fixed wavelength transponder that is operable to transmit channel signals of a single wavelength.

34. An optical network comprising at least one optical cross-connect switch of claim 1, wherein optical fibers couple the optical switching matrices to the optical network via the input and output ports.

35. An optical network comprising at least one optical cross-connect switch of claim 6, wherein optical fibers couple the wavelength division multiplexers and demultiplexers to the optical network for respectively transmitting and receiving said optical output and optical input signals.

36. The optical cross-connect switch of claim 4, wherein:

said switching elements are oriented into a first set of parallel planes;

said switching matrices are oriented into a second set of parallel planes that are orthogonal to the first set of parallel planes; and

each switching matrix of the second set of parallel planes is optically interconnected with each switching element of the first set of parallel planes.

39. A cross-connect switch as defined in claim 1, wherein each switching matrix is operable to switch a signal arriving on any input port to any of a plurality of the inter-matrix output ports.

40. A cross-connect switch as defined in claim 1, wherein each switching matrix is operable to switch a signal arriving on any inter-matrix input port to any of a plurality of the inter-matrix output ports and any of a plurality of the output ports.

16. An optical switching matrix, comprising first and second pairs of switching elements and a plurality of optical combiners;

each pair of switching elements comprising a first switching element and a second switching element;

each switching element comprising;

a rectangular substrate having a plurality of input ports on a first side, a first plurality of output ports on a second side opposite the first side and a second plurality of output ports on a third side adjacent the first side and the second side; and

a plurality of optical diverters aligned between each input port and a corresponding output port on the second side, each diverter being aligned with a respective output port on the third side and being movable from a first position, in which the diverter allows an optical signal incident from the input port to propagate in a direction toward the respective output port on the second side, to a second position, in which the diverter diverts an optical signal incident from the input port toward a respective output port on the third side;

for each of the first and second pairs of switching elements, each input port of the second optical switching element being optically coupled to a respective output port of the first optical switching matrix; and

each combiner being coupled to a respective output port of the first pair of optical switching elements and to a respective output port of the second pair of optical switching elements.

17. An optical switching matrix as defined in claim 16, wherein each combiner is coupled to the respective output port of the first pair of optical switching elements via a first respective WDM multiplexer and is coupled to the respective output port of the second pair of optical switching elements via a second respective WDM multiplexer.

18. A wavelength-converting switch for interconnecting optical switching matrices of an optical cross-connect switch, each optical switching matrix having an inter-matrix input port and an inter-matrix output port, the wavelength-converting switch comprising an optical switch and a plurality of optical transponders connected to the switch:

each optical transponder being operable to convert a channel signal having a first wavelength into a channel signal having a second wavelength; and

the optical switch being operable to couple a channel signal arriving from an inter-matrix output port of any switching matrix to an inter-matrix input port of any of a plurality of other switching matrices via an optical transponder.

19. A wavelength-converting switch as defined in claim 18, wherein the optical switch is operable to couple a channel signal arriving from an inter-matrix output port of any switching matrix to an inter-matrix input port of any other switching matrix via a transponder.

20. A wavelength-converting switch as defined in claim 18, wherein the optical switch is coupled between the inter-matrix output ports and the optical transponders.

21. A wavelength-converting switch as defined in claim 18, wherein the optical switch comprises plural optical switching stages and the optical transponders are coupled between optical switching stages.

22. A wavelength-converting switch as defined in claim 21, wherein the optical switch comprises a multistage CLOS switch.

23. A wavelength-converting switch as defined in claim 18, wherein at least one optical transponder is a tunable optical transponder that is tunable to transmit channel signals of selectable distinct wavelengths.

24. A wavelength-converting switch as defined in claim 18, wherein at least one optical transponder is a fixed wavelength transponder that is operable to transmit channel signals of a single wavelength.

25. A switching fabric for an optical cross-connect switch, the switching fabric comprising a plurality of optical switching matrices, each switching matrix:

having multiple inter-node input ports and at least one intra-node input port for receiving incoming optical channel signals, the incoming optical channel signals having a wavelength that is particular to that particular switching matrix;

having multiple inter-node output ports and at least one intra-node output port; and

being operable to switch optical channel signals arriving on any input port to any of a plurality of the inter-node output ports and the intranode output port.

26. A switching fabric as defined in claim 25, wherein each switching matrix is operable to switch optical channel signals arriving on any input port to any of the output ports.

27. A switching fabric as defined in claim 25, further comprising:

a plurality of wavelength division demultiplexers, each demultiplexer being operable to separate an optical input signal into a plurality of output channel signals having respective distinct wavelengths and to apply each output channel signal to a respective inter-node input port of a respective switching matrix such that each switching matrix receives only channel signals having the respective wavelength that is particular to that switching matrix;

a plurality of wavelength division multiplexers, each multiplexer having a plurality of inputs, each respective input of each multiplexer being coupled to an inter-node output port of a respective switching matrix to receive a respective channel signal having a respective wavelength, each multiplexer being operable to combine channel signals having distinct wavelengths into an optical output signal.

28. A switching fabric as defined in claim 25, further comprising an add/drop multiplexer coupled to the intra-node input port and intranode output port of each switching matrix and being operable:

to couple, to the intra-node input port of any switching matrix of the plurality of switching matrices, optical channel signals having the wavelength that is particular to that switching matrix; and

to receive, from the intra-node output port of any switching matrix of the plurality of switching matrices, optical channel signals having the wavelength that is particular to that switching matrix.

29. A method of cross-connecting optical channel signals at an optical cross-connect switch comprising a plurality of switching matrices, each switching matrix having input ports including at least one inter-node input port and at least one intra-node input port, each switching matrix having output ports including at least one inter-node output port and at least one intra-node output port, wherein the intra-node output ports are coupled to the intra-node input ports, the method comprising:

coupling each optical channel signal having a particular wavelength to an input port of a particular switching matrix assigned to that particular wavelength; and

switching the optical channel signal in the particular switching matrix to either an inter-node output port or an intra-node output port selected according to a desired crossconnection of the optical channel signal.

30. A method as defined in claim 29, wherein the step of switching the optical channel signal comprises switching the optical channel signal to an inter-node output port of the particular switching matrix when the optical channel signal is to be cross-connected to an optical channel having the same particular wavelength.

31. A method as defined in claim 29, wherein the step of switching the optical channel signal comprises switching the optical channel signal to an intra-node output port of the particular switching matrix when the optical channel signal is to be cross-connected to an optical channel having a wavelength other than the particular wavelength of the optical signal.

32. A method as defined in claim 31, further comprising:

coupling the optical signal from the intra-node output port to a wavelength converter;

converting the optical signal to an optical channel signal having another wavelength;

coupling the optical signal at the other wavelength to an intra-node input port of another switching matrix, the other switching matrix being assigned to that other wavelength; and

switching the optical channel signal in the other switching matrix to an output port selected according to the desired cross-connection of the optical channel signal.

33. A method as defined in claim 29, wherein the step of switching the optical channel signal comprises switching the optical channel signal to an intra-node output port of the particular switching matrix when the optical channel signal is to be dropped at the cross-connect switch.

37. A method of upgrading an optical cross-connect switch having a plurality of switching matrices, each switching matrix assigned to -a respective channel wavelength and having multiple input and output ports, the method comprising the steps of:

providing each switching matrix with an expansion port;

providing a plurality of extension switching matrices, each extension switching matrix having multiple input and output ports; and

coupling a respective extension switching matrix to each switching matrix, via said expansion port and at least one of the input ports of the respective extension switching matrix, to form a plurality of expanded switching matrices.

38. The method of claim 37, further comprising the steps of:

providing another optical cross-connect switch having a plurality of said expanded switching matrices; and

coupling each output port of an expanded switching matrix of the optical cross-connect switch to a respective output port of an expanded switching matrix of the another optical cross-connect switch.