Switchable wavelength router

• US 5,912,748 A
• Filed: 12/02/1997
• Issued: 06/15/1999
• Est. Priority Date: 07/23/1996
• Status: Expired due to Fees

• Current Assignee: EZconn Corporation
• Original Assignee: Chorum Technologies, Inc.
• Inventors: Liu, Jian-Yu, Wu, Kuang-Yi
• Primary Examiner(s): BACARES, RAFAEL D
• Application Number:
  US08/982,978
• Time in Patent Office: 560 Days
• Field of Search: 359/117, 359/156, 359/110, 359/115, 359/127, 359/128, 359/245, 359/246, 359/247, 359/251, 359/39
• US Class Current: 398/49
• 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 6/29302 based on birefringence or polarisation, e.g. wavelength dependent birefringence, polarisation interferometers
• CPC Class Codes: G02B 6/29362 Serial cascade of filters or filtering operations, e.g. for a large number of channels
• CPC Class Codes: G02B 6/29395 configurable, e.g. tunable or reconfigurable switching G02B6/35
• CPC Class Codes: G02F 1/31 Digital deflection, i.e. optical switchingG02F1/33 takes precedence
• 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 14/0213 Groups of channels or wave bands arrangements
• CPC Class Codes: H04Q 11/0003 Details
• CPC Class Codes: H04Q 11/0005 Switch and router aspects
• CPC Class Codes: H04Q 2011/0026 using free space propagation (e.g. lenses, mirrors)
• CPC Class Codes: H04Q 2011/0032 using static wavelength routers (e.g. arrayed waveguide grating router [AWGR] )
• CPC Class Codes: H04Q 2011/0035 using miscellaneous components, e.g. circulator, polarisation, acousto/thermo optical

Abstract

A switchable wavelength router has a first polarization-dependent routing element (e.g., a birefringent element, polarized beamsplitter, or angled polarization separator) that decomposes and spatially separates an incoming WDM optical signal into two orthogonally-polarized beams. A first polarization rotator selectably rotates the polarization of one of the beams to match the polarization of other beam, based on an external control signal. A wavelength filter (e.g., stacked waveplates) provides a polarization-dependent optical transmission function such that the first beam decomposes into third and fourth orthogonal beams, and the second beam decomposes into fifth and sixth orthogonal beams. The third and fifth beams carry a first spectral band at a first polarization and the fourth and sixth beams carry a second spectral band at an orthogonal polarization. A second polarization-dependent routing element spatially separates these four beams into four horizontally polarized and vertically polarized components. A second polarization rotator rotates the polarizations of the beams so that the third and fifth beams, and the fourth and sixth beams are orthogonally polarized. A third polarization-dependent routing element recombines the third and fifth beams (i.e., the first spectral band), and also recombines the fourth and sixth beams (i.e., the second spectral band) which are coupled to the two output ports based on the control state of the wavelength router.

Claims

1. An switchable wavelength router selectively directing predetermined spectral bands in an input beam to a plurality of output ports determined by a specified control state, said router comprising:

an input port receiving an input beam;

a first polarization-dependent routing element separating said input beam into a pair of orthogonally-polarized beams; and

a network of wavelength routing switches receiving said pair of beams exiting said first polarization-dependent routing element and having a plurality of output ports, wherein said wavelength routing switches include;

(a) a polarization rotator for selectively rotating the polarization of at least one of a pair of input beams to create first and second beams having the same polarization determined by said control state;

(b) a wavelength filter coupled to receive said first and second beams from said polarization rotator, said wavelength filter having a polarization dependent optical transmission function such that the said first beam decomposes into third and fourth beams with their polarizations orthogonal to each other, and said second beam decomposes into fifth and sixth beams with their polarizations orthogonal to each other, wherein said third and fifth beams carry a first predetermined spectral band at a first polarization and said fourth and sixth beams carry a second predetermined spectral band at a second polarization, wherein said first and second spectral bands are substantially complementary and said first and second polarizations are orthogonal; and

(c) a polarization-dependent routing element spatially routing said third and fifth beams along a first optical path and said fourth and sixth beams along a second optical path based on their polarizations;

wherein said output ports receive a pair of output beams from said network of wavelength routing switches and include;

(a) a polarization rotator for rotating the polarization of at least one of said output beams so that said output beams are orthogonally polarized; and

(b) a polarization-dependent routing element combining said orthogonally-polarized output beams at said output port.

2. The router of claim 1 wherein said wavelength filter comprises a stacked plurality of birefringent waveplates with each waveplate oriented in a predetermined direction.

3. The router of claim 1 wherein said polarization-dependent routing elements comprise a polarized beamsplitter.

4. The router of claim 1 wherein said polarization-dependent routing elements comprise an angled polarization separator.

5. The router of claim 1 wherein said polarization-dependent routing elements comprise a birefringent element.

6. The router of claim 1 wherein said network of wavelength routing switches comprises 1×

2 wavelength routing switches.

7. The router of claim 1 wherein said network of wavelength routing switches comprises a binary tree structure.

8. The router of claim 1 wherein said polarization rotator means comprise a liquid crystal polarization rotator.

9. The router of claim 8 wherein said liquid crystal polarization rotator has a plurality of pixels.

10. A switchable wavelength router comprising:

a first polarization-dependent routing element for receiving an WDM optical signal and decomposing said WDM optical signal into a first beam and a second beam that have orthogonal polarizations and are spatially separated;

a first polarization rotator having a first control state in which the polarization of said first beam is rotated to substantially match the polarization of said second beam, and a second control state in which the polarization of said second beam is rotated to substantially match the polarization of said first beam;

the control state of said first polarization rotator being switchable by an external control signal;

a wavelength filter coupled to receive said first and second beams from said first polarization rotator, said wavelength filter having a polarization dependent optical transmission function such that the said first beam decomposes into third and fourth beams with their polarizations orthogonal to each other, and said second beam decomposes into fifth and sixth beams with their polarizations orthogonal to each other, wherein said third and fifth beams carry a first predetermined spectral band at a first polarization and said fourth and sixth beams carry a second predetermined spectral band at a second polarization, wherein said first and second spectral bands are substantially complementary and said first and second polarizations are orthogonal;

a second polarization-dependent routing element for spatially separating said third, fourth, fifth, and sixth beams into four horizontally polarized and vertically polarized components;

a second polarization rotator for rotating the polarizations of said third, fourth, fifth, and sixth beams such that said third and fifth beams are orthogonally polarized and said fourth and sixth beams are orthogonally polarized; and

a third polarization-dependent routing element for receiving said third, fourth, fifth, and sixth beams from said second polarization rotator, spatially recombining said third and fifth beams containing said first spectral band, and spatially recombining said fourth and sixth beams containing said second spectral band.

11. The router of claim 10 wherein said first polarization rotator further comprises:

a first area for rotating the polarization of said first beam in said first control state, and passing said first beam without rotation in said second control state; and

a second area for passing said second beam without rotation in said first control state, and rotating the polarization of said second beam in said second control state.

12. The router of claim 10 wherein said second polarization rotator further comprises:

(a) a first area for rotating the polarization of said fifth beam;

(b) a second area for rotating the polarization of said sixth beam;

(c) a third are for passing said third beam without rotation; and

(b) a fourth area for passing said fourth beam without rotation.

13. The router of claim 10 wherein said wavelength filter comprises a stacked plurality of birefringent waveplates with each waveplate oriented in a predetermined direction.

14. The router of claim 10 wherein said polarization-dependent routing element comprises a birefringent element.

15. The router of claim 10 wherein said polarization-dependent routing element comprises a polarized beamsplitter.

16. The router of claim 10 wherein said polarization-dependent routing element comprises an angled polarized separator.