Compact wavelength-selective optical crossconnect

• US 7,212,703 B2
• Filed: 02/07/2005
• Issued: 05/01/2007
• Est. Priority Date: 08/13/2002
• Status: Active Grant

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Wu, Ming-Chiang
• Primary Examiner(s): Kim; Ellen E.
• Application Number:
  US11/053,048
• Publication Number:
  US 20070036480A1
• Time in Patent Office: 813 Days
• Field of Search: 385/16, 385/18
• US Class Current: 385/16
• CPC Class Codes: G02B 6/3512 the optical element being reflective, e.g. mirror
• CPC Class Codes: G02B 6/3556 NxM switch, i.e. regular arrays of switches elements of matrix type constellation
• CPC Class Codes: H04J 14/0212 using optical switches or wavelength selective switches [WSS]
• CPC Class Codes: H04J 14/0213 Groups of channels or wave bands arrangements
• CPC Class Codes: H04Q 11/0005 Switch and router aspects
• CPC Class Codes: H04Q 2011/0016 using wavelength multiplexing or demultiplexing
• CPC Class Codes: H04Q 2011/0024 using space switching
• CPC Class Codes: H04Q 2011/003 using switches based on microelectro-mechanical systems [MEMS]
• CPC Class Codes: H04Q 2011/0052 Interconnection of switches

Abstract

A system and method of optically routing wavelength channels from within a plurality of optical inputs to any of a plurality of optical outputs. An optical wavelength-selective cross connect (WSXC) switch is described with a first stage of wavelength division multiplexing (WDM) routers which support an optical input and a plurality of optical outputs, which are interconnected to a second stage of WDM routers having a plurality of optical inputs and an optical output. The wavelength channel is routed in two stages from one of the input stage routers to an output stage router for output. It should be appreciated that the WSXC switch of the invention can be utilized for passing optical signals in either direction. In a preferred implementation integrated circuit router chips are stacked into cubes to form the routers stages which are cross coupled using a twisted butt joint to form a WSXC switch.

Claims

1. An optical wavelength selective switch, comprising:

a first router block;

said first router block comprising a first plurality of optical wavelength division multiplexing (WDM) routers, each said router having at least one optical input and a plurality of optical outputs, each said router configured to receive an optical input signal and route individual wavelength channels in said optical signal to said optical outputs; and

a second router block;

said second router block comprising a second plurality of optical wavelength division multiplexing (WDM) routers, each said router having a plurality of optical inputs and at least one optical output, each said router configured to route individual wavelength channels received on said optical inputs to a said optical output;

wherein said first and second router blocks are joined to one another at an optical interface in which an array of optical waveguides in said first router block are cross-coupled to optical waveguides in said second router block; and

wherein said cross-coupled first and second router blocks are configured to optically switch selected wavelength channels from within a plurality of optical inputs to said first router block into any of a plurality of optical outputs on said second router block.

2. An apparatus as recited in claim 1:

wherein said optical interface comprises rows and column of optical waveguides;

wherein rows of optical waveguides in said first router block are cross-coupled to columns of optical waveguides in said second router block;

wherein columns of optical waveguides in said second router block are cross-coupled to rows of optical waveguides in said second router block.

3. An apparatus as recited in claim 1, further comprising a one-dimensional array of optical fiber connections on said optical interface for each said first router block and said second router block through which optical signals are input and output.

4. An apparatus as recited in claim 3, wherein each said router block is integrated on a substrate comprising:

an optical waveguide for each wavelength channel;

at least one dispersive element;

a slab waveguide; and

a focusing lens configured to direct wavelengths to and from a one axis array of micromirrors for switching wavelength channels between an optical input and a plurality of optical outputs.

5. An apparatus as recited in claim 4, wherein said dispersive element is selected from the group of dispersive elements consisting essentially of microfabricated gratings, prisms, and photonic crystals.

6. An apparatus as recited in claim 4, further comprising a spacer joined to said substrate to match the pitch between waveguides on stacked router chips to the pitch between waveguides on a single said router integrated on a substrate.

7. An apparatus as recited in claim 1, wherein said optical inputs and said optical outputs comprise optical fiber connections.

8. An apparatus as recited in claim 1, further comprising means for modulating routing paths within said first plurality of routers and said second plurality of routers to direct specified wavelength channels from said optical inputs in said first plurality of routers for output from said plurality of outputs in said second plurality of routers.

9. An apparatus as recited in claim 8, wherein said means for modulating comprises:

a computer processor coupled to said first and second plurality of routers and configured for receiving wavelength channel switching commands; and

programming executable by said computer processor for carrying out the operations of,

mapping an optical transmission path from said optical inputs in said first plurality of optical routers to said optical outputs in said second plurality of optical routers in response to said wavelength channel switching commands, and

configuring the routing of said first plurality of routers and said second plurality of routers in response to said mapping.

10. An apparatus for optically switching selected wavelength channels from a plurality of optical inputs to a plurality of optical outputs, comprising:

a first router stage having a first plurality of optical wavelength division multiplexing (WDM) routers, each said WDM router in said first stage configured to receive an optical input and route individual wavelength channels therein for output on one of a plurality of optical outputs;

a second router stage having a second plurality of optical wavelength division multiplexing (WDM) routers, each said WDM router in said second stage having a plurality of optical inputs and configured for routing individual wavelength channels therein for output on an optical output;

an optical interface on each of said first and second router stages;

a one-dimensional array of optical fiber connections on said optical interface which is configured for coupling optical fibers to said first and second router stages for inputting and outputting optical signals;

a two-dimensional array of optical waveguides on said optical interface, said array of optical waveguides configured for optically cross-coupling said first and second router stages when said first and second router stages are joined to one another; and

means for modulating routing paths within said first and second router stages to optically switch specified wavelength channels from the plurality of inputs of said first router stage for output from any of the plurality of optical outputs from said second router stage.

11. An apparatus as recited in claim 10:

wherein each router, within said first plurality of optical wavelength division multiplexing (WDM) routers, are joined to one another in a stack to form said first router stage; and

wherein each router, within said second plurality of optical wavelength division multiplexing (WDM) routers, are joined to one another in a stack to form said second router stage.

12. An apparatus as recited in claim 10:

wherein said optical interface comprises rows and column of optical waveguides;

wherein rows of optical waveguides in said first router stage are joined across columns of optical waveguides in said second router stage; and

wherein columns of optical waveguides in said first router stage are joined across rows of optical waveguides in said second router stage.

13. An apparatus as recited in claim 12, wherein each of said optical wavelength division multiplexing routers within said first and second router stages is integrated on a substrate comprising:

an optical waveguide for each wavelength channel;

at least one dispersive element;

a slab waveguide; and

a focusing lens configured to direct wavelengths to and from a one axis array of micromirrors for switching wavelength channels between an optical input and a plurality of optical outputs.

14. An apparatus as recited in claim 13, wherein said dispersive element is selected from the group of dispersive elements consisting essentially of microfabricated gratings, prisms, and photonic crystals.

15. An apparatus as recited in claim 13, further comprising a spacer joined to said substrate to match the pitch between waveguides on stacked router chips to the pitch between waveguides on a single said integrated router.

16. An apparatus as recited in claim 10, wherein said one-dimensional array of optical fiber connections comprises an optical fiber connection on the edge of each optical wavelength division multiplexing (WDM) router within a stack formed of said routers within each of said first router stage and said second router stage.

17. An apparatus as recited in claim 10, wherein said means for modulating comprises:

a computer processor having outputs coupled to said first and second router stage and configured for receiving wavelength channel switching commands; and

programming executable by said computer processor for carrying out the operations of,

mapping an optical transmission path from said optical inputs of said first router stage to said optical outputs of said second router stage in response to said wavelength channel switching commands, and

configuring routing of said first and second router stage in response to said mapping.

18. An apparatus for optically switching wavelength channels from within a plurality of optical inputs into any of a plurality of optical outputs, comprising:

a first router stage having a first plurality of optical wavelength division multiplexing (WDM) routers, each said WDM router within said first router stage receiving an optical input and configured to route individual wavelength channels for output on one of a plurality of optical outputs; and

a second router stage having a second plurality of WDM routers, each said WDM router within said second router stage being optically coupled to said first stage of routers and having an optical input connection to each of said WDM routers within said first router stage, wherein each of said WDM routers within said second router stage is configured for routing selected wavelength channels received from one router within said first router stage to an optical output from said second router stage;

an optical interface on each of said first and second router stages;

a one-dimensional array of optical fiber connections on said optical interface which is configured for coupling optical fibers to said first and second router stages for inputting and outputting optical signals; and

a two-dimensional array of optical waveguides on said optical interface, said array of optical waveguides configured for optically cross-coupling said first and second router stages when said first and second stages router stages are joined to one another;

wherein said first plurality of routers are joined to one another in a stack to form said first router stage, and said second plurality of routers are joined to one another in a stack to form said second router stage;

wherein rows of optical waveguides in said first router stage are joined across columns of optical waveguides in said second router stage; and

wherein columns of optical waveguides in said first router stage are joined across rows of optical waveguides in said second router stage.

19. An apparatus as recited in claim 18, wherein each router is configured with a row of waveguides, said waveguides within the row having a predetermined first distance from one another according to a first pitch.

20. An apparatus as recited in claim 18, wherein the spacing between routers in said stack forming said first and second router stages is equal to said first pitch.

21. An apparatus as recited in claim 18:

wherein said one-dimensional array of optical fiber connections comprises an optical fiber connection on the edge of each router within said stack of each said first and second router stages.

22. An apparatus as recited in claim 18, wherein each of said wavelength division multiplexing (WDM) routers is fabricated as a monolithic circuit.

23. An apparatus as recited in claim 22, wherein each said monolithic circuit is fabricated using micro-electromechanical systems fabrication techniques.

24. An apparatus as recited in claim 22, wherein a micromirror array for optically directing wavelength channels from an input to an output is externally coupled to a stack of said monolithic circuits in fabricating said wavelength division multiplexing routers.

25. An apparatus as recited in claim 22, wherein said first stage of said wavelength division multiplexing routers comprises a stack of said monolithic wavelength division multiplexing routers to which a micromirror array is coupled.

26. An apparatus as recited in claim 22, wherein said second stage of said wavelength division multiplexing routers comprises a stack of said monolithic wavelength division multiplexing routers to which a micromirror array is coupled.

27. An apparatus as recited in claim 26:

wherein said second router stage is joined at an optical interface to said first router stage with a preparatory twist of ninety degrees to make the monolithic wavelength division multiplexing routers of the first router stage oriented at right angles to said second router stage, said first and second router stages being joined at a butt coupling.

28. An apparatus as recited in claim 27, wherein each of said plurality of optical wavelength division multiplexing (WDM) routers within said first and second router stages is integrated on a substrate comprising:

optical waveguides for each wavelength channel;

at least one dispersive element;

a slab waveguide; and

a focusing lens configured to direct wavelengths to and from a one axis array of micromirrors for switching wavelength channels between an optical input and a plurality of optical outputs.

29. An apparatus as recited in claim 28, wherein said dispersive element is selected from the group of dispersive elements consisting essentially of microfabricated gratings, prisms, and photonic crystals.

30. An apparatus as recited in claim 28, further comprising a spacer joined to said substrate to match the pitch between waveguides on stacked router chips to the pitch between waveguides on a single said router.

31. An apparatus as recited in claim 18, wherein each wavelength division multiplexing (WDM) optical router within said first router stage has one optical input and N optical outputs, each said optical output being optically coupled to one of N optical inputs on each of N optical routers forming said second router stage.

32. An apparatus as recited in claim 18, wherein the optical waveguides of said optical two-dimensional array comprise a regular two dimensional waveguide array given by:

W_0,a, W_0,b, W_0,c, . . . W_0,n

W_1,a, W_1,b, W_1,c, . . . W_1,n

W_2,a, W_2,b, W_2,c, . . . W_2,n

. . .

W_n,a, W_n,b, W_n,c, . . . W_n,n

wherein subscripts a, b, c, . . . n each denote a row of individual waveguide optical connections on a single router, and wherein subscripts 0, 1, 2, 3, . . . n denote each router in said stack of routers forming each column of waveguides in said stack of routers.

33. An apparatus as recited in claim 18, further comprising means for modulating the routing paths within said first router stage and said second router stage to direct specified wavelength channels from the plurality of inputs of said first router stage for output from the plurality of outputs from said second router stage.

34. An apparatus as recited in claim 33, wherein said means comprises:

a computer processor having outputs coupled to said first router stage and said second router stage of optical routers and configured for receiving wavelength channel switching commands; and

programming executable by said computer processor for carrying out the operations of

mapping an optical transmission path from said optical inputs of said first router stage of said wavelength division multiplexing (WDM) routers to said optical output from said second router stage of said wavelength division multiplexing (WDM) routers in response to said wavelength channel switching commands, and

configuring the routing of said first router stage and said second router stage in response to said mapping.

35. An apparatus for optically switching wavelength channels, comprising:

a first router stage wherein a plurality of optical wavelength division multiplexing (WDM) routers, fabricated monolithically on substrates, are stacked together;

a second router stage wherein a plurality of optical wavelength division multiplexing (WDM) routers integrated on substrates are stacked together; and

a cross coupled optical connection between said first router stage and said second router stage, wherein said stack of integrated optical routers for said first and said second router stages are joined together in a butt coupling after rotating the first and second router stages to approximately ninety degrees in relation to one another;

wherein wavelength channels from a given optical router within said first router stage are optically coupled to each optical router within said second router stage; and

wherein any of a plurality of wavelength channels from a group of optical fiber inputs are cross connectable to a group of optical fiber outputs.

36. An apparatus as recited in claim 35, further comprising:

an optical interface on each of said first and second router stages;

a one-dimensional array of optical fiber connections on said optical interface which is configured for coupling optical fibers to said first and second router stages for inputting and outputting optical signals; and

an array of optical waveguides on said optical interface, said array having rows of optical waveguides on each router and columns of waveguides formed across the stack of routers;

wherein said cross coupled optical connection is formed by joining the first and second router stages so that the rows of waveguides from the first router stage are aligned with the columns of waveguides from the second router stage, and that the columns of waveguides from the first router stage are aligned with the rows of waveguides from the second router stage.

37. An apparatus as recited in claim 35, wherein each of said plurality of optical wavelength division multiplexing (WDM) routers in said first and second router stages is fabricated monolithically on a substrate comprising:

optical waveguides for each wavelength channel;

at least one dispersive element;

a slab waveguide; and

a focusing lens configured to direct wavelengths to and from a one axis array of micromirrors for switching wavelength channels between an optical input and a plurality of optical outputs.

38. An apparatus as recited in claim 37, wherein a micromirror array for optically directing wavelength channels from an input to an output is externally coupled to a stack of said integrated circuits in fabricating each of said first router stage and said second router stage.

39. An apparatus as recited in claim 37, wherein said dispersive element is selected from the group of dispersive elements consisting essentially of microfabricated gratings, prisms, and photonic crystals.

40. An apparatus as recited in claim 37, further comprising a spacer joined to said substrate so that the spacing between waveguides on adjacent stacked integrated optical routers match the spacing between adjacent waveguides on a single said integrated optical router.

41. An apparatus as recited in claim 35, wherein each wavelength division multiplexing (WDM) optical router within said first routing stage has one optical input and N optical outputs, each said optical output being optically coupled to one of N optical inputs on each of N optical routers forming said second routing stage.

42. A method of optically switching wavelength channels from within a plurality of input channels to any of a plurality of output channels, comprising:

receiving optical signals at each of N optical routers in a first router stage;

routing separate wavelength channels received at said first router stage to selected one of N×

N optical outputs at an optical interface of said first router stage;

rotating said first router stage in relation to a second router stage;

interconnecting said N×

N optical outputs of said first stage to N×

N optical inputs at each of N optical routers in a second router stage; and

routing separate wavelength channels received at the N×

N optical inputs of each said optical router of said second router stage to an optical output;

wherein rows within the N×

N optical outputs of said first router stage are interconnected with columns within the N×

N optical inputs of said second router stage, and wherein columns within the N×

N optical outputs of said first router stage are interconnected with rows within the N×

N optical inputs of said second router stage.

43. A method as recited in claim 42, wherein any wavelength channel received at any of the N optical routers of said first router stage can be routed for output from any of the N optical routers within said second router stage.

44. A method as recited in claim 42, wherein each said stage of optical routers comprises a stack of integrated optical router chips.

45. A method as recited in claim 44, wherein a micromirror array comprising a plurality of single axis micromirrors is optically coupled within each stage of integrated circuits after said integrated circuits are stacked together.

46. A method as recited in claim 44, wherein each optical router stage comprises:

a plurality of substrates stacked together,

optical waveguides fabricated on each said substrate,

at least one dispersive element optically coupled to said optical waveguide,

a slab waveguide fabricated on each said substrate,

a focusing lens coupling receiving optical wavelengths through said slab waveguide; and

a plurality of single axis micromirrors for switching wavelength channels between an optical inputs and optical outputs within each substrate.

47. A method as recited in claim 42, wherein on said interconnection any wavelength channel received at any of the N optical routers of said first router stage can be routed for output from any of the N optical routers of said second router stage.

48. A method as recited in claim 42, wherein said routing comprises:

communicating wavelength channel switching commands to said first and second router stages; and

mapping an optical transmission path from said optical inputs of said first router stage to said optical output from said second router stage in response to said wavelength channel switching command.

49. A method of interconnecting two-dimensional arrays of optical waveguides from integrated wavelength division multiplex routers in a cross-coupled configuration, comprising:

stacking a first plurality of optical substrates, each having a plurality of waveguide optical connections extending from wavelength division multiplex routers;

stacking a second plurality of optical substrates, each having a plurality of waveguide optical connections extending from wavelength division multiplex routers;

wherein when joined in said stacked configuration a two dimensional array of waveguide optical connections is created on an optical interface;

wherein said optical interface is adapted for receiving optical fibers;

wherein opposite the optical interface end of the optical substrates in the stacked configuration is joined a two-dimensional micromirror array for directing channels to one of the outputs on an input stack, or from one of the inputs on an output stack;

rotating said first plurality of optical substrates in relation to said second plurality of optical substrates; and

joining the stack of said first plurality of optical substrates to the stack of said second plurality of optical substrates forming a cross-connected set of interconnects.

50. A method as recited in claim 49, further comprising configuring the spacing of optical waveguides on each of said optical substrates to match the spacing between each substrate in the stack of said plurality of said optical substrates, wherein upon rotating the two interfaces the waveguides on any given substrate can be aligned with a waveguide on each of said substrates in the stack of said plurality of said optical substrates.

51. A method as recited in claim 50, wherein said spacing configuration comprises adding a spacer to each substrate so that the spacing of substrates in the stack match the spacing between waveguides on a given substrate.

52. A method as recited in claim 49, wherein the waveguides of a first plurality of optical substrates may be considered a regular two dimensional waveguide array given by:

W_0,a, W_0,b, W_0,c, . . . W_0,n

W_1,a, W_1,b, W_1,c, . . . W_1,n

W_2,a, W_2,b, W_2,c, . . . W_2,n

. . .

W_n,a, W_n,b, W_n,c, . . . W_n,n

wherein subscripts a, b, c, . . . n denote the individual waveguide optical connections on a single substrate, and wherein subscripts 0, 1, 2, 3, . . . n denote each optical substrate in the stack of said plurality of optical substrates.

53. A method as recited in claim 52, wherein said cross-connected set of waveguide interconnects may be described by:

W_0,a-Y_0,n, W_0,b-Y_1,n, W_0,c,-Y_2,n, . . . W_0,n-Y_n,n

W_1,a-Y_0,n-1, W_1,b-Y_1,n-1, W_1,c,-Y_2,n-1, . . . W_1,n-Y_n,n-1

W_2,a-Y_0,n-2, W_2,b-Y_1,n-2, W_2,c,-Y_2,n-2, . . . W_2,n-Y_n,n-2,

. . .

W_n,a-Y_0,a W_n,b-Y_1,a, W_n,c-Y_2,a, . . . W_n,n-Y_n,a

wherein the “

-”

sign represents a connection established between waveguides in the n×

n array of waveguides, with array W representing waveguide optical connections on a said first plurality of optical substrates and array Y representing waveguide optical connections on said second plurality of optical substrates.