Polarization control apparatus and associated method

• US 6,526,187 B1
• Filed: 05/17/2001
• Issued: 02/25/2003
• Est. Priority Date: 05/17/2001
• Status: Expired due to Term

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Optronx Inc.
• Inventors: Deliwala, Shrenik
• Primary Examiner(s): Kim, Robert H.
• Assistant Examiner(s): KIM, RICHARD H
• Application Number:
  US09/859,663
• Publication Number:
  US 20030031394A1
• Time in Patent Office: 649 Days
• Field of Search: 385/11, 385/12, 385/14, 385/1, 385/2
• US Class Current: 385/11
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: G02B 2006/12038 Glass (SiO2 based materials)
• CPC Class Codes: G02B 2006/12061 Silicon
• CPC Class Codes: G02B 2006/12097 Ridge, rib or the like
• CPC Class Codes: G02B 2006/12104 Mirror; Reflectors or the like
• CPC Class Codes: G02B 2006/12107 Grating
• CPC Class Codes: G02B 2006/12114 Prism
• CPC Class Codes: G02B 2006/12135 Temperature control
• CPC Class Codes: G02B 2006/12161 Distributed feedback [DFB]
• CPC Class Codes: G02B 2006/12164 Multiplexing; Demultiplexing
• CPC Class Codes: G02B 2006/12176 Etching
• CPC Class Codes: G02B 27/285 comprising arrays of elements, e.g. microprisms
• CPC Class Codes: G02B 5/045 Prism arrays
• CPC Class Codes: G02B 6/10 of the optical waveguide type G02B6/02, G02B6/24 take precedence; devices or arrangements for the control of light by electric, magnetic, electro-magnetic or acoustic means G02F1/00; transferring the modulation of modulated light G02F2/00; optical logic elements G02F3/00; optical analogue/digital converters G02F7/00
• CPC Class Codes: G02B 6/12004 Combinations of two or more optical elements
• CPC Class Codes: G02B 6/12007 forming wavelength selective elements, e.g. multiplexer, demultiplexer
• CPC Class Codes: G02B 6/12011 characterised by the arrayed waveguides, e.g. comprising a filled groove in the array section
• CPC Class Codes: G02B 6/12016 characterised by the input or output waveguides, e.g. tapered waveguide ends, coupled together pairs of output waveguides
• CPC Class Codes: G02B 6/12026 characterised by means for reducing the temperature dependence
• CPC Class Codes: G02B 6/12028 based on a combination of materials having a different refractive index temperature dependence, i.e. the materials are used for transmitting light
• CPC Class Codes: G02B 6/12033 : characterised by means for configuring the device, e.g. moveable element for wavelength tuning switching G02B6/35; thermo-optic devices G02F1/0147
• CPC Class Codes: G02B 6/1225 : comprising photonic band-gap structures or photonic lattices
• CPC Class Codes: G02B 6/1228 : Tapered waveguides, e.g. integrated spot-size transformers for coupling with fibres G02B6/305
• CPC Class Codes: G02B 6/124 : Geodesic lenses or integrated gratings
• CPC Class Codes: G02B 6/272 : comprising polarisation means for beam splitting and combining
• CPC Class Codes: G02B 6/2861 : using fibre optic delay lines and optical elements associated with them, e.g. for use in signal processing, e.g. filtering delay lines in general H03H, H01P9/00; optical computing devices G06E
• CPC Class Codes: G02B 6/29325 : of the slab or planar or plate like form, i.e. confinement in a single transverse dimension only integrated circuit planar waveguide arrangements G02B6/12007; specially adapted for lighting G02B6/0011
• CPC Class Codes: G02B 6/29349 : Michelson or Michelson/Gires-Tournois configuration, i.e. based on splitting and interferometrically combining relatively delayed signals at a single beamsplitter
• CPC Class Codes: G02B 6/29358 : Multiple beam interferometer external to a light guide, e.g. Fabry-Pérot, etalon, VIPA plate, OTDL plate, continuous interferometer, parallel plate resonator G02B6/29347, G02B6/29349, G02B6/2935, G02B6/29361 take precedence; resonator evanescently coupled to light guide G02B6/29335
• CPC Class Codes: G02B 6/29391 : Power equalisation of different channels, e.g. power flattening
• CPC Class Codes: G02B 6/29395 : configurable, e.g. tunable or reconfigurable switching G02B6/35
• CPC Class Codes: G02B 6/34 : utilising prism or grating G02B6/293 takes precedence
• CPC Class Codes: G02B 6/4232 : using the surface tension of fluid solder to align the elements, e.g. solder bump techniques flip-chip mounting techniques in assembly of semiconductor devices H01L24/81
• CPC Class Codes: G02B 6/43 : Arrangements comprising a plurality of opto-electronic elements and associated optical interconnections
• CPC Class Codes: G02F 1/0147 : based on thermo-optic effects G02F1/132 takes precedence
• CPC Class Codes: G02F 1/0152 : using free carrier effects, e.g. plasma effect
• CPC Class Codes: G02F 1/025 : in an optical waveguide structure G02F1/017, G02F1/2257 take precedence
• CPC Class Codes: G02F 1/295 : Analog deflection from or in an optical waveguide structure]
• CPC Class Codes: G02F 2201/20 : delay line
• CPC Class Codes: H01L 27/1203 : the substrate comprising an insulating body on a semiconductor body, e.g. SOI three-dimensional layout H01L27/0688

Abstract

An optical polarization controller apparatus and associated method that controls a first temporal separation between a first polarization and a second polarization of an output optical signal, wherein a second temporal separation exists between a first polarization and a second polarization of an input optical signal. The optical polarization controller comprises a controller, a polarization separation device, and a delay element. The controller determines the first temporal separation. The controller compares the first temporal separation with the second temporal separation. The polarization separation device transmits the first polarization of the output optical signal along a first path and transmits the second polarization of the output optical signal along a second path. The delay element delays the first polarization of the output optical signal relative to the second polarization of the output optical signal whereby a duration of the first temporal separation becomes closer to a duration of the second temporal separation. The delay element further comprising a gate electrode and a voltage source. The gate electrode has a prescribed electrode shape positioned proximate the waveguide. The voltage source is connected to the gate electrode for applying voltage to the gate electrode, wherein the voltage causes the gate electrode to project into the waveguide the region of changeable propagation constant, said region of changeable propagation constant corresponding generally in shape to the prescribed electrode shape. The controller controls the propagation constant level of the region of changeable propagation constant by varying the voltage applied to the gate electrode wherein changing the propagation constant level of the region of changeable propagation constant changes a duration that the first polarization of the output optical signal is delayed within the region of changeable propagation constant.

Claims

1. An optical polarization controller that controls a first temporal separation between a first polarization and a second polarization of an output optical signal, wherein a second temporal separation exists between a first polarization and a second polarization of an input optical signal, the optical polarization controller comprising:

a controller that determines the first temporal separation, the controller compares the first temporal separation with the second temporal separation;

a polarization separation device that transmits the first polarization of the output optical signal along a first path and transmits the second polarization of the output optical signal along a second path; and

a delay element that delays the first polarization of the output optical signal relative to the second polarization of the output optical signal whereby a duration of the first temporal separation becomes closer to a duration of the second temporal separation, the delay element further comprising;

a waveguide that includes an input port wherein the input optical signal is introduced into the waveguide, an output port wherein an optical signal exits the waveguide, and a region of changeable propagation constant disposed along a length of the waveguide and between the input port and the output port, wherein the input optical signal is guided by total internal reflection in the waveguide, and the waveguide is formed at least in part from an active semiconductor,

a first electrode positioned proximate a first surface of the region of changeable propagation constant and electrically separated from the active semiconductor,

a second electrode in electrical contact with the active semiconductor and disposed on a first side of the region of changeable propagation constant,

a two-dimensional electron (hole) gas (2DEG) having a free carrier distribution that is formed on the first surface of the active semiconductor when a voltage is applied between the first electrode and the second electrode, and

wherein changing the voltage causes a corresponding change of the free carrier distribution which, in turn, causes corresponding change of a propagation constant level in the region of changeable propagation constant that changes a duration that the first polarization of the output optical signal is flowing through the region of changeable propagation constant.

2. The optical polarization controller of claim 1, further comprising a third electrode in electrical contact with the active semiconductor disposed on a second side of the region of changeable propagation constant opposite the first side;

wherein the second and third electrodes are electrically coupled to a common potential.

3. The optical polarization controller of claim 1 or 2, wherein the 2DEG is oriented in a plane that is substantially parallel to a length of said waveguide.

4. The optical polarization controller of claim 2, further comprising a field effect transistor (FET) portion that includes the first, second, and third electrodes.

5. The optical polarization controller of claim 4, wherein the FET portion is from one of the group of metal-oxide-semiconductor FET (MOSFET), metal-electrical insulator-semiconductor FET (MISFET), a metal semiconductor field effect transistor (MESFET), a high electron mobility transistor (HEMT), or a modulation doped FET (MODFET).

6. The optical polarization controller of claim 1, further comprising a metal oxide semiconductor capacitor (MOSCAP) portion.

7. The optical polarization controller of claim 6, wherein the body contact electrode is located below the waveguide.

8. The optical polarization controller of claim 1, wherein the waveguide comprises any group III or group V semiconductor.

9. The optical polarization controller of claim 1, wherein the free-carrier distribution of the 2DEG layer is varied by changing the voltage applied to the first electrode, and wherein light flowing through the waveguide is controllably attenuated in response to the voltage applied to the first electrode.

10. The optical polarization controller of claim 1 that includes a combiner that combines the first polarization of the output optical signal with the second polarization of the output optical signal after the first polarization of the output optical signal has passed through the delay element.

11. The optical filter of claim 10, wherein the combiner includes an arrayed waveguide.

12. The optical filter of claim 1, wherein the delay element includes a programmable delay generator.

13. The optical filter of claim 1, wherein the delay element of the first path includes a first programmable delay generator, and wherein the second path includes a second programmable delay generator, the first programmable delay generator and the second programmable delay generator are individually controlled by the controller to control the relative delay between the first polarization flowing in the first path and the second polarization flowing in the second path.

14. An optical polarization controller that controls a first temporal separation between a first polarization and a second polarization of an output optical signal, wherein a second temporal separation exists between a first polarization and a second polarization of an input optical signal, the optical polarization controller comprising:

a controller the determines the first temporal separation, the controller compares the first temporal separation with the second temporal separation;

a polarization separation device that transmits the first polarization of the output optical signal along a first path and transmits the second polarization of the output optical signal along a second path; and

a delay element that delays the first polarization of the output optical signal relative to the second polarization of the output optical signal whereby a duration of the first temporal separation becomes closer to a duration of the second temporal separation, the delay element further comprising;

a gate electrode having a prescribed electrode shape positioned proximate the waveguide,

a voltage source connected to the gate electrode for applying voltage to the gate electrode, wherein the voltage causes the gate electrode to project into the waveguide the region of changeable propagation constant, said region of changeable propagation constant corresponding generally in shape to the prescribed electrode shape, and

the controller controls the propagation constant level of the region of changeable propagation constant by varying the voltage applied to the gate electrode wherein changing the propagation constant level of the region of changeable propagation constant changes a duration that the first polarization of the output optical signal is delayed within the region of changeable propagation constant.

15. The optical polarization controller of claim 14 that includes a combiner that combines the first polarization of the output optical signal with the second polarization of the output optical signal after the first polarization of the output optical signal has passed flowed through the delay element.

16. The optical filter of claim 15, wherein the combiner includes an arrayed waveguide.

17. The optical filter of claim 14, wherein the delay element includes a programmable delay generator.

18. The optical filter of claim 14, wherein the delay element of the first path includes a first programmable delay generator, and wherein the second path includes a second programmable delay generator, the first programmable delay generator and the second programmable delay generator are individually controlled by the controller to control the relative delay between the first polarization flowing in the first path and the second polarization flowing in the second path.

19. The optical filter of claim 14, wherein a 2DEG is oriented in a plane that is substantially parallel to the region of changeable propagation constant.

20. The optical polarization controller of claim 14, further comprising a field effect transistor (FET) portion including a source electrode and a drain electrode.

21. The optical polarization controller of claim 14, wherein the FET is from one of the group of metal-oxide-semiconductor FET (MOSFET), metal-electrical insulator-semiconductor FET (MISFET), a metal semiconductor field effect transistor (MESFET), a high electron mobility transistor (HEMT), or a modulation doped FET (MODFET).

22. The optical polarization controller of claim 14, further comprising one or more body contact electrode(s) positioned relative to the waveguide and electrically integrated with an active semiconductor.

23. The optical polarization controller of claim 14, further comprising a metal oxide semiconductor capacitor (MOSCAP) portion that includes the body contact electrode.

24. The optical polarization controller of claim 14, wherein the body contact electrode is located below the waveguide.

25. The optical polarization controller of claim 14, wherein the body contact electrode includes a first body contact electrode and a second body contact electrode, the first body contact electrode, the gate electrode, and the second body contact electrode are located above the waveguide.

26. The optical polarization controller of claim 25, wherein the first body contact electrode is located on an opposed side of the gate electrode from the second body contact electrode, and wherein the waveguide comprises any group III or group V semiconductor.

27. The optical polarization controller of claim 19, wherein the free-carrier distribution of the 2DEG layer is varied by changing the voltage applied to the gate electrode, and wherein light flowing through the waveguide is controllably attenuated in response to the voltage applied to the gate electrode.

28. The optical polarization controller of claim 14, further comprising an optical device coupled with a variable coupling to the optical polarization controller.

29. A method for controlling a first temporal separation between a first polarization and a second polarization of an output optical signal, wherein a second temporal separation exists between a first polarization and a second polarization of an input optical signal, the method comprising:

determining the first temporal separation;

comparing the first temporal separation with the second temporal separation;

transmitting the first polarization of the output optical signal along a first path and transmitting the second polarization of the output optical signal along a second path; and

delaying the first polarization of the output optical signal relative to the second polarization of the output optical signal wherein a duration of the first temporal separation following the delaying becomes closer to a duration of the second temporal separation, the delaying further comprising;

positioning a planar electrode proximate the waveguide,

applying a voltage to the planar electrode to change a level of propagation constant in a region of changeable propagation constant in the waveguide wherein the region of changeable propagation constant corresponds in shape to a shape of the planar electrode, and

controlling a propagation constant level of the region of changeable propagation constant by varying the voltage wherein changing the propagation constant level of the region of changeable propagation constant changes a duration that the first polarization of the output optical signal is delayed within the region of changeable propagation constant.

30. The method of claim 29, further comprising a 2DEG located between the planar electrode and a body contact electrode, wherein the 2DEG is oriented in a plane that is substantially parallel to a length of the region of changeable propagation constant.

31. The method of claim 29, further comprising a field effect transistor (FET) portion including the planar electrode.

32. The method of claim 31, wherein the FET is from one of the group of metal-oxide-semiconductor FET (MOSFET), metal-electrical insulator-semiconductor FET (MISFET), a metal semiconductor field effect transistor (MESFET), a high electron mobility transistor (HEMT), or a modulation doped FET (MODFET).

33. The method of claim 29, further comprising one or more body contact electrode(s) positioned relative to the waveguide and electrically integrated with an active semiconductor.

34. The method of claim 33, further comprising a metal oxide semiconductor capacitor (MOSCAP) portion including the body contact electrode.

35. The method of claim 34, wherein the body contact electrode is positioned below the waveguide.

36. The method of claim 34, wherein the body contact electrode includes a first body contact electrode and a second body contact electrode, the first body contact electrode, the planar electrode, and the second body contact electrode are located above the waveguide;

and the first body contact electrode is located on an opposed side of the planar electrode from the second body contact electrode.

37. The method of claim 29, wherein the waveguide comprises any group III or group V semiconductor.

38. The method of claim 30, wherein the free-carrier distribution of the 2DEG layer is changed by changing the voltage applied to the planar electrode, and wherein light flowing through the waveguide is controllably changed in response to changing the free-carrier distribution of the 2DEG layer.

39. The method of claim 29, further comprising an optical device coupled with a variable coupling to the optical polarization controller.

40. A computer readable medium for controlling a first temporal separation between a first polarization and a second polarization of an output optical signal, wherein a second temporal separation exists between a first polarization and a second polarization of an input optical signal, said software when executed by a processor causes the processor to perform the steps of:

determining the first temporal separation, the controller compares the first temporal separation with the second temporal separation;

transmitting the first polarization of the output optical signal along a first path and transmitting the second polarization of the output optical signal along a second path; and

delaying the first polarization of the output optical signal relative to the second polarization of the output optical signal wherein the duration of the first temporal separation following the delaying becomes closer to the duration of the second temporal separation, the delaying further comprising;

projecting a region of changeable propagation constant into the waveguide that corresponds in shape to a shape of an electrode, by applying a voltage to the electrode, and

controlling a propagation constant level of the region of changeable propagation constant by varying the voltage wherein changing the propagation constant level of the region of changeable propagation constant changes a duration that the first polarization of the output optical signal is delayed within the region of changeable propagation constant.

41. An optical polarization controller that controls a first temporal separation between a first polarization and a second polarization of an output optical signal, wherein a second temporal separation exists between a first polarization and a second polarization of an input optical signal, the optical polarization controller comprising:

a controller that determines the first temporal separation, the controller compares the first temporal separation with the second temporal separation;

a polarization separation device that transmits the first polarization of the output optical signal along a first path and transmits the second polarization of the output optical signal along a second path; and

a delay element that delays the first polarization of the output optical signal relative to the second polarization of the output optical signal wherein a duration of the first temporal separation becomes closer to a duration of the second temporal separation, the delay element further comprising;

a region of changeable propagation constant disposed along a length of a waveguide, wherein light is guided within the waveguide by total internal reflection, and the waveguide is formed at least in part from an active semiconductor;

a Field Effect Transistor portion (FET portion) including a gate electrode, a source electrode, and a drain electrode;

the gate electrode is mounted to, but electrically insulated from, the active semiconductor;

the drain electrode and the source electrode are held at a substantially common voltage;

wherein the gate electrode, the source electrode, and the drain electrode are positioned substantially above the waveguide, the source electrode is located on a substantially opposed side of the gate electrode from the drain electrode;

a two-dimensional electron (hole) gas (2DEG) having a free carrier distribution that is formed on the first surface of a active semiconductor proximate the gate electrode when a voltage is applied between the gate electrode and the common voltage;

a voltage source connected to the gate electrode for applying the voltage to the gate electrode, wherein the gate electrode projects the region of changeable propagation constant into the waveguide; and

wherein the controller controls the propagation constant level of the region of changeable propagation constant by varying the voltage produced by the voltage source, wherein changing the propagation constant level of the region of changeable propagation constant changes a duration that the first polarization of the output optical signal is delayed within the region of changeable propagation constant.

42. The optical polarization controller of claim 41 further including a combiner that combines the first polarization of the output optical signal with the second polarization of the output optical signal after the first polarization of the output optical signal has passed through the delay element.

43. The optical filter of claim 42, wherein the combiner includes an arrayed waveguide.

44. The optical filter of claim 41, wherein the delay element includes a programmable delay generator.

45. The optical filter of claim 41, wherein the delay element of the first path includes a first programmable delay generator, and wherein the second path includes a second programmable delay generator, the first programmable delay generator and the second programmable delay generator are individually controlled by the controller to control a relative delay between the first polarization flowing in the first path and the second polarization flowing in the second path.

46. An apparatus that controls a first temporal separation between a first polarization and a second polarization of an output optical signal, wherein a second temporal separation exists between a first polarization and a second polarization of an input optical signal, the apparatus comprising:

means for determining the first temporal separation, and for comparing the first temporal separation with the second temporal separation;

means for transmitting the first polarization of the output optical signal along a first path and transmitting the second polarization of the output optical signal along a second path; and

means for delaying the first polarization of the output optical signal relative to the second polarization of the output optical signal wherein a duration of the first temporal separation becomes closer to a duration of the second temporal separation, the means for delaying further comprising;

a planar electrode positioned proximate the waveguide;

means for changing a region of changeable propagation constant in the waveguide that substantially corresponds in shape to a shape of the planar electrode by applying a voltage to the planar electrode; and

means for controlling a propagation constant level of the region of changeable propagation constant by varying the voltage wherein changing the propagation constant level of the region of changeable propagation constant changes a duration that the first polarization is delayed within the region of changeable propagation constant.

47. A method for controlling a first temporal separation between a first polarization and a second polarization of an output optical signal, wherein a second temporal separation exists between a first polarization and a second polarization of an input optical signal, the method comprising:

determining the first temporal separation;

comparing the first temporal separation with the second temporal separation;

transmitting the first polarization of the output optical signal along a first path and transmitting the second polarization of the output optical signal along a second path; and

delaying the first polarization of the output optical signal relative to the second polarization of the output optical signal wherein a duration of the first temporal separation following the delaying becomes closer to a duration of the second temporal separation, the delaying further comprising;

providing a gate electrode proximate the waveguide;

providing a body contact electrode proximate the waveguide;

applying the input optical signal to the waveguide;

applying a changeable voltage to the gate electrode that generates a region of changeable propagation constant in the waveguide; and

delaying the first polarization as it passes through the region of changeable propagation constant in response to the voltage.

48. An apparatus that controls a first temporal separation between a first polarization and a second polarization of an output optical signal, wherein a second temporal separation exists between a first polarization and a second polarization of an input optical signal, the apparatus comprising:

means for determining the first temporal separation, and for comparing the first temporal separation with the second temporal separation;

means for transmitting the first polarization of the output optical signal along a first path and transmitting the second polarization of the output optical signal along a second path; and

means for delaying the first polarization of the output optical signal relative to the second polarization of the output optical signal wherein a duration of the first temporal separation becomes closer to a duration of the second temporal separation, the means for delaying further comprising;

a planar electrode positioned proximate the waveguide;

means for applying a voltage to the planar electrode to change a level of propagation constant in a region of changeable propagation constant in the waveguide wherein the region of changeable propagation constant corresponds in shape to a shape of the planar electrode; and

means for controlling a propagation constant level of the region of changeable propagation constant by varying the voltage, wherein changing the propagation constant level of the region of changeable propagation constant changes a duration that the first polarization of the output optical signal is delayed within the region of changeable propagation constant.

49. An apparatus that controls a first temporal separation between a first polarization and a second polarization of an output optical signal, wherein a second temporal separation exists between a first polarization and a second polarization of an input optical signal, the apparatus comprising:

a first path including a first delay element;

a second path including a second delay element;

a beamsplitter that separates the input optical signal into a first polarized signal including a first polarization and a second polarized signal including the second polarization wherein the first polarized signal is applied to the first path and the second polarized signal is applied to the second path;

a controller the determines the first temporal separation, the controller compares the first temporal separation with the second temporal separation;

a first delay element that delays the first polarization of the first polarized signal relative to the second polarization of the second polarized signal, the first delay element further comprising;

a first gate electrode having a first prescribed electrode shape positioned proximate a first waveguide,

a first voltage source connected to the first gate electrode for applying a first voltage to the first gate electrode, wherein the first voltage causes the first gate electrode to project into the first waveguide a first region of changeable propagation constant, said first region of changeable propagation constant corresponding generally in shape to the prescribed electrode shape of the first gate electrode, and

wherein the controller controls a propagation constant level of the first region of changeable propagation constant by varying the first voltage applied to the first gate electrode wherein changing the propagation constant level of the first region of changeable propagation constant changes a duration that the first polarized signal is delayed within the first region of changeable propagation constant; and

a second delay element that delays the second polarization of the second polarized signal relative to the first polarization of the first polarized signal, the second delay element further comprising;

a second gate electrode having a second prescribed electrode shape positioned proximate a second waveguide,

a second voltage source connected to the second gate electrode for applying a second voltage to the second gate electrode, wherein the second voltage causes the second gate electrode to project into the second waveguide a second region of changeable propagation constant, said second region of changeable propagation constant corresponding generally in shape to the prescribed electrode shape of the second gate electrode, and

wherein the controller controls a propagation constant level of the second region of changeable propagation constant by varying the second voltage applied to the second gate electrode wherein changing the second propagation constant level of the second region of changeable propagation constant changes a duration that the second polarized signal is delayed within the second region of changeable propagation constant.

50. The optical polarization controller of claim 49 that includes a combiner that combines the first polarization of the first polarized signal with the second polarization of the second polarized signal after the first polarization of the first polarized signal has passed through the first delay element and the second polarization of the second polarization signal has passed through the second delay element.

51. The optical filter of claim 50, wherein the combiner includes an arrayed waveguide.

52. The optical filter of claim 49, wherein the first delay element includes a programmable delay generator.

53. The optical filter of claim 49, wherein the first delay element includes a first programmable delay generator, and wherein the second second delay element includes a second programmable delay generator, the first programmable delay generator and the second programmable delay generator are individually controlled by the controller to control the relative delay between the first polarization flowing in the first path and the second polarization flowing in the second path.

54. A method for controlling a first temporal separation between a first polarization and a second polarization of an output optical signal, wherein a second temporal separation exists between a first polarization and a second polarization of an input optical signal, the method comprising:

separating an input optical signal into a first polarized signal including a first polarization and a second polarized signal including the second polarization wherein the first polarized signal is applied to a first path and the second polarization signal is applied to a second path;

determining the first temporal separation;

comparing the first temporal separation with the second temporal separation;

delaying the first polarization of the first polarized signal relative to the second polarization of the second polarized signal, the delaying further comprising;

positioning a first gate electrode having a prescribed electrode shape proximate a first waveguide,

connecting a first voltage source to the first gate electrode and applying a first voltage to the first gate electrode, wherein the first voltage causes the first gate electrode to project into the first waveguide a first region of changeable propagation constant, said first region of changeable propagation constant corresponding generally in shape to the prescribed electrode shape of the first gate electrode, and

controlling a propagation constant level of the first region of changeable propagation constant by varying the first voltage wherein changing the propagation constant level of the first region of changeable propagation constant changes a duration that the first polarization of the first polarized signal is delayed within the first region of changeable propagation constant; and

delaying the second polarization of the second polarized signal relative to the first polarization of the first polarized signal, the delaying further comprising;

providing a second gate electrode having a prescribed electrode shape proximate a second waveguide,

connecting a second voltage source to the second gate electrode and applying a second voltage to the second gate electrode, wherein the second voltage causes the second gate electrode to project into the second waveguide a second region of changeable propagation constant, said second region of changeable propagation constant corresponding generally in shape to the prescribed electrode shape of the second gate electrode, and

controlling a propagation constant level of the second region of changeable propagation constant by varying the second voltage wherein changing the second propagation constant level of the second region of changeable propagation constant changes a duration that the second polarization of the second polarization signal is delayed within the second region of changeable propagation constant.

55. The method of claim 54 that includes combining the first polarization of the first polarization signal with the second polarization of the second polarization signal after the first polarization of the first polarization signal has passed flowed through the first delay element and the second polarization of the second polarization signal has passed through the second delay element.

56. The method of claim 55, wherein the combining is performed by an arrayed waveguide.

57. The method of claim 54, wherein the delaying the first polarization is performed by a programmable delay generator.

58. The method of claim 54, wherein a controller individually controls the relative delay between the first polarization flowing in the first path and the second polarization flowing in the second path.