Wavelength selective optical switch

• US 7,468,840 B2
• Filed: 06/25/2002
• Issued: 12/23/2008
• Est. Priority Date: 10/09/2001
• Status: Expired due to Term

• Current Assignee: II-VI Delaware, Inc. (Coherent Corp.)
• Original Assignee: Xtellus Inc.
• Inventors: Corem, Yossi, Cohen, Gil, Silberberg, Yaron
• Primary Examiner(s): FINEMAN, LEE A
• Application Number:
  US10/492,484
• Publication Number:
  US 20050036202A1
• Time in Patent Office: 2,373 Days
• Field of Search: None
• US Class Current: 359/489.08
• CPC Class Codes: G02B 6/272 comprising polarisation means for beam splitting and combining
• CPC Class Codes: G02B 6/2766 Manipulating the plane of polarisation from one input polarisation to another output polarisation, e.g. polarisation rotators, linear to circular polarisation converters
• CPC Class Codes: G02B 6/2931 Diffractive element operating in reflection
• CPC Class Codes: G02B 6/29311 Diffractive element operating in transmission
• CPC Class Codes: G02B 6/29313 characterised by means for controlling the position or direction of light incident to or leaving the diffractive element, e.g. for varying the wavelength response switching G02B6/35
• CPC Class Codes: G02B 6/2938 for multiplexing or demultiplexing, i.e. combining or separating wavelengths, e.g. 1xN, NxM
• CPC Class Codes: G02B 6/29395 configurable, e.g. tunable or reconfigurable switching G02B6/35
• CPC Class Codes: G02F 1/1326 Liquid crystal optical waveguides or liquid crystal cells specially adapted for gating or modulating between optical waveguides
• CPC Class Codes: G02F 1/31 Digital deflection, i.e. optical switchingG02F1/33 takes precedence
• CPC Class Codes: G02F 2203/05 wavelength dependent
• CPC Class Codes: H04Q 11/0005 Switch and router aspects
• CPC Class Codes: H04Q 2011/0024 using space switching
• CPC Class Codes: H04Q 2011/0035 using miscellaneous components, e.g. circulator, polarisation, acousto/thermo optical

Abstract

A wavelength selective switch, in which an input optical signal is wavelength-dispersed and polarization-split in two angularly oriented planes. A polarization rotation device, such as a liquid crystal polarization modulator, pixelated along the wave-length dispersive direction such that each pixel operates on a separate wavelength channel, rotates the polarization of the light signal passing through the pixel, according to the control voltage applied to that pixel. The polarization modulated signals are then wave-length-recombined and polarization-recombined by means of similar dispersion and polarization combining components as were used to respectively disperse and split the input signals. The direction of the output signal is determined by whether the polarization of a particular wavelength channel was rotated by the polarization modulator pixel, or not. In this way, a fast, wavelength dependent, optical switch is provided, capable of use in WDM switching applications.

Claims

1. A wavelength dependent switch, comprising in sequence:

a polarization beam splitter having at least a first input port, for receiving at least one input beam having at least two wavelength components, said polarization beam splitter being operative to spatially split each of said at least one input beam into a pair of beams of separate polarization components,

a first dispersive element receiving said pair of beams of separate polarization components, and operative to spatially disperse said wavelength components of each of said pair of beams of separate polarization components in a dispersion plane disposed at an angle to the plane in which said polarization components are split;

a first focusing element receiving said wavelength components of each of said pair of beams of separate polarization components from said first dispersion element, without any intervening polarization manipulation element;

a polarization modulating element disposed in the focal region of said first focusing element, without any intervening polarization dependent deflection element between said first focusing element and said polarization modulating element, said polarization modulating element being pixelated generally along the direction of the dispersion such that each pixel is associated with a separate wavelength component, each pixel of said polarization modulating element being operative to change the state of the polarization of light passing through said pixel according to a control signal applied to said pixel;

a second focusing element receiving said light after passing through said polarization modulating element;

a second dispersive element receiving light from said second focusing element, and operative to combine said separate wavelength components of each of said pair of beams into multi-wavelength beams; and

a polarization beam combiner having two output ports, said polarization beam combiner receiving each of said pair of multi-wavelength beams, and operative to combine said separate polarization components such that each wavelength component of said at least one input beam is directed to one of said two output ports according to the control signal applied to said pixel associated with said wavelength.

2. A wavelength dependent switch according to claim 1, wherein said polarization modulating element is a liquid crystal element.

3. A wavelength dependent switch according to claim 1, wherein said angle is such that said dispersion plane is essentially orthogonal to said plane in which said polarization components are split.

4. A wavelength dependent switch according to claim 1, wherein said separate polarization components are two orthogonal components.

5. A wavelength dependent switch according to claim 1, wherein said polarization beam splitter also comprises a second input port, such that said switch is operative to switch a wavelength component of a signal input to either of said first and said second input ports, to either of said output ports, according to the control signal applied to said pixel associated with said wavelength component.

6. A wavelength dependent switch according to claim 1 and also comprising a half wave plate disposed in juxtaposition to said polarization modulating element, operative to reduce polarization dependent losses in the switch.

7. A wavelength dependent switch according to claim 1, and also comprising a first half wave plate disposed in the path of one of said pair of beams of separate polarization components emerging from said polarizing beam spliffer;

and a second half wave plate disposed in the path of another one of said pair of beams of separate polarization components entering said polarizing beam combiner, such that polarization dependent losses in the switch are reduced.

8. A wavelength dependent switch according to claim 1 and wherein at least one of said input beams is input to said switch by means of a multiple fiber collimator, such that said switch operates as a multiply parallel wavelength selective switch.

9. A wavelength dependent switch module comprising a plurality of wavelength dependent switches according to claim 1, and wherein at least two of said wavelength dependent switches utilize a common one of at least one of a dispersive element, a focusing element and a polarization modulating element.

10. A wavelength dependent switch according to claim 1 and wherein at least one of said polarization beam splitter and said polarization beam combiner is of a split prism construction.

11. A wavelength dependent switch according to claim 1 and wherein at least one of said polarization beam splitter and said polarization beam combiner is of birefringent crystal construction.

12. A wavelength dependent switch according to claim 1 and wherein said at least one input beam comprises one input beam, such that said switch operates as a 1×

2switch.

13. A wavelength dependent switch according to claim 1 and wherein said at least one input beam comprises one input beam, and only one of said two output ports is used such that said switch operates as a 1×

1 switch.

14. A wavelength dependent switch according to claim 1 and wherein said at least one input beam comprises two input beams, such that said switch operates as a 2×

2switch.

15. A wavelength dependent switch, comprising in sequence:

a polarization beam splitter having a first and second port, at least one of said ports receiving an input beam comprising at least two wavelength components, said polarization beam splitter being operative to spatially split each of said at least one input beam into a pair of beams of separate polarization components;

a dispersive element receiving said pair of beams of separate polarization components, and operative to spatially disperse said wavelength components of each of said pair of beams of separate polarization components in a dispersion plane disposed at an angle to the plane in which said polarization components are split;

a focusing element receiving said wavelength components of each of said pair of beams of separate polarization components from said dispersion element, without any intervening polarization manipulation element;

a polarization modulating element disposed in the focal region of said focusing element without any intervening polarization dependent deflection element between said focusing element and said polarization modulating element, said polarization modulating element being pixelated generally along the direction of the dispersion such that each pixel is associated with a separate wavelength component, each pixel of said polarization modulating element being operative to change the state of the polarization of light passing through said pixel according to a control signal applied to said pixel; and

a reflecting surface operative to reflect said light back in sequence through said pixelated polarization modulating element, said focusing element, said dispersive element and said polarization beam splitter, such that each wavelength component of said light is output to one of said first and second ports according to the control signal applied to said pixel associated with said wavelength.

16. A wavelength dependent switch according to claim 15, wherein said polarization modulating element is a liquid crystal element.

17. A wavelength dependent switch according to claim 15, wherein said angle is such that said dispersion plane is essentially orthogonal to said plane in which said polarization components are split.

18. A wavelength dependent switch according to claim 15, wherein said separate polarization components are two orthogonal components.

19. A wavelength dependent switch according to claim 15 and also comprising a circulator disposed at at least one of said first and second ports, such that said input beam at said at least one of said first and second ports is separated from light output to said at least one of said first and second ports.

20. A wavelength dependent switch according to claim 15 and also comprising a dual fiber collimator disposed at at least one of said first and second ports, such that said input beam light at said at least one of said first and second ports is separated from light output to said at least one of said first and second ports.

21. A wavelength dependent switch module comprising a plurality of wavelength dependent switches according to claim 15 and wherein at least two of said wavelength dependent switches utilize a common one of at least one of a dispersive element, a focusing element and a polarization modulating element.

22. A wavelength dependent switch according to claim 15 and wherein said at least one input beam comprises one input beam, such that said switch operates as a 1×

2 switch.

23. A wavelength dependent switch according to claim 15 and wherein said at least one input beam comprises one input beam, and only one of said first and second ports is used to output light, such that said switch operates as a 1×

1 switch.

24. A wavelength dependent switch according to claim 15 and wherein said at least one input beam comprises two input beams, such that said switch operates as a 2×

2 switch.

25. A wavelength dependent switch according to claim 15 and also comprising a quarter wave plate disposed in juxtaposition to said polarization modulating element, operative to reduce polarization dependent losses in the switch.

26. A wavelength dependent switch, comprising in sequence:

a polarization beam splitter having at least a first input port, for receiving at least one input beam having at least two wavelength components, and operative to spatially split each of said at least one input beam into a pair of beams of separate polarization components,

a first dispersive element receiving said pair of beams of separate polarization components, and operative to spatially disperse said wavelength components of each of said pair of beams of separate polarization components in a dispersion plane disposed at an angle to the plane in which said polarization components are split;

a first focusing element receiving said wavelength components of each of said pair of beams of separate polarization components;

a polarization modulating element disposed in the focal region of said first focusing element, said polarization modulating element being pixelated generally along the direction of the dispersion such that each pixel is associated with a separate wavelength component, each pixel of said polarization modulating element being operative to change the state of the polarization of light passing through said pixel according to a control signal applied to said pixel;

a second focusing element receiving said light after passing through said polarization modulating element;

a second dispersive element receiving light from said second focusing element, and operative to combine said separate wavelength components of each of said pair of beams into multi-wavelength beams; and

a polarization beam combiner having two output ports, said polarization beam combiner receiving each of said pair of multi-wavelength beams, and operative to combine said separate polarization components such that each wavelength component of said at least one input beam is directed to one of said two output ports according to the control signal applied to said pixel associated with said wavelength;

wherein said separate polarization components directed to a first one of said two output ports traverse essentially the same optical paths into said polarization beam combiner as those of said separate polarization components directed to a second one of said output ports.

27. A wavelength dependent switch according to claim 26, wherein said polarization beam splitter also comprises a second input port, such that said switch is operative to switch a wavelength component of a signal input to either of said first and said second input ports, to either of said output ports, according to the control signal applied to said pixel associated with said wavelength component, and

wherein said spatially split polarization components of said input beams from said first input port traverse essentially the same optical paths on exiting said polarization beam splitter as those of said spatially split polarization components of said input beams from said second input port.

28. A wavelength dependent switch, comprising in sequence:

a polarization beam splitter having a first and second port, at least one of said ports receiving an input beam comprising at least two wavelength components, and operative to spatially split each of said at least one input beam into a pair of beams of separate polarization components;

a dispersive element receiving said pair of beams of separate polarization components, and operative to spatially disperse said wavelength components of each of said pair of beams of separate polarization components in a dispersion plane disposed at an angle to the plane in which said polarization components are split;

a focusing element receiving said wavelength components of each of said pair of beams of separate polarization components;

a polarization modulating element disposed in the focal region of said focusing element, said polarization modulating element being pixelated generally along the direction of the dispersion such that each pixel is associated with a separate wavelength component, each pixel of said polarization modulating element being operative to change the state of the polarization of light passing through said pixel according to a control signal applied to said pixel; and

a reflecting surface operative to reflect said light back in sequence through said pixelated polarization modulating element, said focusing element, said dispersive element and said polarization beam splitter, such that each wavelength component of said light is output to one of said first and second ports according to the control signal applied to said pixel associated with said wavelength;

wherein said spatially split polarization components of said input beams from said first input port traverse essentially the same optical paths on exiting said polarization beam splitter as those of said spatially split polarization components of said input beams from said second input port.

29. A wavelength dependent switch, comprising in sequence:

a polarization beam splitter having a first and second port, at least one of said ports receiving an input beam comprising at least two wavelength components, said polarization beam splitter being operative to spatially split each of said at least one input beam into a pair of beams of separate polarization components;

a dispersive element receiving said pair of beams of separate polarization components, and operative to spatially disperse said wavelength components of each of said pair of beams of separate polarization components in a dispersion plane disposed at an angle to the plane in which said polarization components are split;

a focusing element receiving said wavelength components of each of said pair of beams of separate polarization components from said first dispersion element;

a polarization modulating element disposed in the focal region of said focusing element without any intervening polarization dependent deflection element between said focusing element and said polarization modulating element, said polarization modulating element being pixelated generally along the direction of the dispersion such that each pixel is associated with a separate wavelength component, each pixel of said polarization modulating element being operative to change the state of the polarization of light passing through said pixel according to a control signal applied to said pixel; and

a reflecting surface operative to reflect said light back in sequence through said pixelated polarization modulating element, said focusing element, said dispersive element and said polarization beam splitter, such that each wavelength component of said light is output to one of said first and second ports according to the control signal applied to said pixel associated with said wavelength,

wherein said spatially split polarization components of said input beam from said first input port traverse essentially the same optical paths within said switch after exiting said polarization beam splitter as those of said spatially split polarization components of said input beam from said second input port.