Optical processing

• US 8,335,033 B2
• Filed: 02/23/2010
• Issued: 12/18/2012
• Est. Priority Date: 09/03/2001
• Status: Expired due to Term

• Current Assignee: Thomas Swan & Company Limited (Aixtron AG)
• Original Assignee: Thomas Swan & Company Limited (Aixtron AG)
• Inventors: Holmes, Melanie
• Primary Examiner(s): Ben, Loha
• Application Number:
  US12/710,913
• Publication Number:
  US 20100209109A1
• Time in Patent Office: 1,029 Days
• Field of Search: 359/3, 359/9, 359/11, 359237-239, 359/279, 359/556, 359/558, 359/559, 359/566, 359/24, 359/29, 385 15- 18, 385/22, 385/31, 385/43, 385/129, 385/133, 385/146, 385/147, 385/901, 356/326, 356/328, 362/26, 362/602, 369/103, 369/44.29, 369/100, 398/49, 398/79
• US Class Current: 359/279
• CPC Class Codes: G02B 26/06 for controlling the phase of light G02B26/08 takes precedence , measuring optical phase difference G01J9/00
• CPC Class Codes: G02B 26/0808 by means of one or more diffracting elements
• CPC Class Codes: G02B 26/0833 the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD G02B26/0825 takes precedence; micromechanical devices in general B81B
• CPC Class Codes: G02B 5/32 Holograms used as optical elements
• CPC Class Codes: G02B 6/266 the optical element being an attenuator
• CPC Class Codes: G02B 6/29311 Diffractive element operating in transmission
• CPC Class Codes: G02B 6/29314 by moving or modifying the diffractive element, e.g. deforming
• CPC Class Codes: G02B 6/2938 for multiplexing or demultiplexing, i.e. combining or separating wavelengths, e.g. 1xN, NxM
• CPC Class Codes: G02B 6/29391 Power equalisation of different channels, e.g. power flattening
• CPC Class Codes: G02B 6/3512 the optical element being reflective, e.g. mirror
• CPC Class Codes: G02B 6/3534 the optical element being diffractive, i.e. a grating
• CPC Class Codes: G02B 6/3548 1xN switch, i.e. one input and a selectable single output of N possible outputs
• CPC Class Codes: G02B 6/3556 NxM switch, i.e. regular arrays of switches elements of matrix type constellation
• 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 1/13342 Holographic polymer dispersed liquid crystals
• CPC Class Codes: G02F 1/1335 Structural association of cells with optical devices, e.g. polarisers or reflectors
• CPC Class Codes: G02F 1/29 for the control of the position or the direction of light beams, i.e. deflection
• CPC Class Codes: G02F 1/291 Two-dimensional analogue deflection
• CPC Class Codes: G02F 1/31 Digital deflection, i.e. optical switchingG02F1/33 takes precedence
• CPC Class Codes: G02F 1/3132 of directional coupler type
• CPC Class Codes: G02F 2201/30 : grating
• CPC Class Codes: G02F 2201/34 : reflector
• CPC Class Codes: G02F 2203/12 : spatial light modulator
• CPC Class Codes: G02F 2203/28 : focussing or defocussing
• CPC Class Codes: G02F 2203/50 : Phase-only modulation
• CPC Class Codes: G03H 1/0005 : Adaptation of holography to specific applications holographic optical element G02B5/32; holographic scanner G02B26/106; recognition using holographic mask G06V10/88; holographic memories G11B7/0065, G11C13/042
• CPC Class Codes: G03H 1/02 : Details of features involved during the holographic process; Replication of holograms without interference recording
• CPC Class Codes: G03H 1/04 : Processes or apparatus for producing holograms G03H1/26 takes precedence
• CPC Class Codes: G03H 1/08 : Synthesising holograms, i.e. holograms synthesized from objects or objects from hologramsusing electric digital computers G06F; G06T
• CPC Class Codes: G03H 1/0866 : Digital holographic imaging, i.e. synthesizing holobjects from holograms
• CPC Class Codes: G03H 1/0891 : Processes or apparatus adapted to convert digital holographic data into a hologram G03H1/2294 takes precedence
• CPC Class Codes: G03H 1/2286 : Particular reconstruction light G03H1/24 takes precedence; Beam properties
• CPC Class Codes: G03H 1/2294 : Addressing the hologram to an active spatial light modulator
• CPC Class Codes: G03H 1/26 : Processes or apparatus specially adapted to produce multiple sub- holograms or to obtain images from them, e.g. multicolour technique
• CPC Class Codes: G03H 2001/0224 : Active addressable light modulator, i.e. Spatial Light Modulator [SLM] corresponding details, see subgroups of G03H2225/00
• CPC Class Codes: G03H 2001/0491 : by monitoring the hologram formation, e.g. via a feed-back loop
• CPC Class Codes: G03H 2001/261 : in optical contact
• CPC Class Codes: G03H 2001/264 : One hologram being a HOE
• CPC Class Codes: G03H 2222/13 : Multi-wavelengths wave with discontinuous wavelength ranges G03H2222/18 takes precedence
• CPC Class Codes: G03H 2222/32 : Unpolarised light
• CPC Class Codes: G03H 2223/23 : Diffractive element
• CPC Class Codes: G03H 2225/32 : Phase only
• CPC Class Codes: G03H 2225/52 : Reflective modulator
• CPC Class Codes: G03H 2225/60 : Multiple SLMs
• CPC Class Codes: G03H 2226/02 : Computing or processing means, e.g. digital signal processor [DSP]
• CPC Class Codes: H04J 14/021 : Reconfigurable arrangements, e.g. reconfigurable optical add/drop multiplexers [ROADM] or tunable optical add/drop multiplexers [TOADM]
• 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: H04J 14/0217 : Multi-degree architectures, e.g. having a connection degree greater than two
• CPC Class Codes: H04J 14/0219 : Modular or upgradable architectures
• CPC Class Codes: H04J 14/022 : For interconnection of WDM optical networks
• CPC Class Codes: H04J 14/08 : Time-division multiplex systems
• 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 2011/0028 : using holograms
• CPC Class Codes: H04Q 2011/0039 : Electrical control

Abstract

A modular routing node includes a single input port and a plurality of output ports. The modular routing node is arranged to produce a plurality of different deflections and uses small adjustments to compensate for wavelength differences and alignment tolerances in an optical system. An optical device is arranged to receive a multiplex of many optical signals at different wavelengths, to separate the optical signals into at least two groups, and to process at least one of the groups adaptively.

Claims

1. An optical processor having a reflective SLM, a dispersion device and a focussing device, wherein the SLM has an array of controllable elements, wherein the processor is configured such that light from a common point on the dispersion device is spatially distributed over at least part of the SLM, and wherein the processor is configured such that the controllable elements display different holograms at chosen locations of the SLM where said light is incident, for controlling directions at which light from respective said locations emerges.

2. The optical processor of claim 1, having control circuitry adapted to provide plural different holograms to the SLM.

3. The optical processor of claim 2, wherein said plural different holograms include respective holograms each for performing a different function, whereby controllable elements at respective chosen locations of the SLM may operate as selected ones of the group comprising:

an optical add/drop multiplexer, an optical monitoring device, a channel equaliser, a channel controller, a programmable optical source, a programmable optical filter, an optical spectrum analyser, an evaluation device, a reconfigurable wavelength demultiplexer, and a reconfigurable wavelength multiplexer.

4. The optical processor of claim 2, wherein said plural different holograms are each displayed at the same time on a respective two-dimensional group of controllable elements at respective chosen locations of the SLM, wherein each hologram performs a different operation on a respective beam of light incident on the group of controllable elements where the hologram is displayed.

5. The optical processor of claim 4, wherein at least one hologram causes the optical processor to perform the function of a routing device.

6. The optical processor of claim 5, wherein the said function of a routing device comprises 1:

N routing.

7. The optical processor of claim 5, wherein the said function of a routing device comprises N:

1 routing.

8. The optical processor of claim 4, wherein at least one hologram causes the optical processor to perform the function of adding a wavelength channel.

9. The optical processor of claim 4, wherein at least one hologram causes the optical processor to perform the function of dropping a wavelength channel.

10. The optical processor of claim 4, wherein at least one hologram causes the optical processor to perform the function of an optical monitoring device.

11. The optical processor of claim 4, wherein at least one hologram causes the optical processor to perform the function of a channel equalizer.

12. The optical processor of claim 4, wherein at least one hologram causes the optical processor to perform the function of a channel controller.

13. The optical processor of claim 4, wherein at least one hologram causes the optical processor to perform the function of a programmable optical source.

14. The optical processor of claim 4, wherein at least one hologram causes the optical processor to perform the function of a programmable optical filter.

15. The optical processor of claim 4 wherein at least one hologram causes the optical processor to perform the function of an optical spectrum analyzer.

16. The optical processor of claim 4 wherein at least one hologram causes the optical processor to perform the function of an evaluation device.

17. The optical processor of claim 4 wherein at least one hologram causes the optical processor to perform the function of a reconfigurable wavelength demultiplexer.

18. The optical processor of claim 4 wherein at least one hologram causes the optical processor to perform the function of a reconfigurable wavelength multiplexer.

19. The optical processor of claim 1, having a single SLM.

20. The optical processor of claim 1, having more than one SLM, each having a respective array of controllable elements wherein the processor is configured such that light from a common point on the dispersion device is spatially distributed over at least part of each SLM.

21. The optical processor of claim 1, configured so that said light from a common point on the dispersion device is substantially collimated by the focusing device when incident upon the SLM.

22. The optical processor of claim 1, further comprising at least one light sensor arranged to provide signals indicative of emergent light.

23. The optical processor of claim 22, wherein the at least one light sensor is arranged to provide signals indicative of light specularly reflected at the SLM.

24. The optical processor of claim 1, wherein the SLM is a Liquid Crystal on Silicon SLM.

25. The optical device of claim 1, wherein the SLM incorporates a quarter wave-plate.

26. The optical processor of claim 1, wherein each hologram occupies an array of controllable elements that has between 10 and 50 controllable elements in at least one dimension.

27. The optical processor of claim 1, wherein each hologram occupies an array of controllable elements that has a size in at least one dimension that is at least 2 times the 1/e spot half-width of the amplitude distribution of an incident beam in a corresponding direction.

28. The optical processor of claim 1, wherein the controllable elements are phase-modulating elements.

29. The optical processor of claim 1 wherein the reflective SLM has a two-dimensional array of controllable elements, wherein the reflective SLM is configured such that each controllable element is selectable whereby two-dimensional groups of controllable elements are formed at chosen locations of the reflective SLM;

wherein the processor is configured such that, using the focusing device, light from a common point on the dispersion device is spatially distributed by wavelength across at least one of the two-dimensional groups, and wherein the processor is configured such that each of the two-dimensional groups of controllable elements displays a different hologram at a chosen location of the reflective SLM.

30. The optical processor of claim 29 having control circuitry operable to select controllable elements to delineate said two-dimensional groups of controllable elements, and to vary one of the delineation of the groups and the selection of control data giving rise to the different holograms whereby upon illumination of said groups by respective light beams, respective emergent light beams from the groups are controllable independently of each other.

31. The optical processor of claim 29 having control circuitry operable to select controllable elements to delineate said two-dimensional groups of controllable elements, and to vary both of the delineation of the groups and the selection of control data giving rise to the different holograms whereby upon illumination of said groups by respective light beams, respective emergent light beams from the groups are controllable independently of each other.

32. The optical processor of claim 29 wherein the processor is configured such that, using the focusing device, light from a common point on the dispersion device is spatially distributed by wavelength across each of the two-dimensional groups wherein the spatial distribution extends across at least two of the two-dimensional groups.

33. The optical processor of claim 29, further comprising at least one input and at least one output, and control circuitry operable to control how wavelengths of light received from said at least one input appear at said at least one output.

34. The optical processor of claim 33 further comprising a broadband optical source operable to render light incident at the at least one input, the processor being operable to transfer incident light from the at least one input to said at least one output, and further comprising control circuitry operable to select wavelengths of light transferred.

35. The optical processor of claim 33, wherein the optical processor is operable to perform at least one of:

producing a desired output spectrum and synthesizing a comb spectrum.

36. The optical processor of claim 35, wherein the optical processor is operable to vary the spectrum of light emerging from the at least one output.

37. The optical processor of claim 35, having plural broadband optical sources arranged to render light incident at the plural inputs, the optical processor being arranged to transfer light from its inputs to said at least one output, and further comprising control circuitry operable to select wavelengths of light transferred.

38. The optical processor of claim 33, further comprising control circuitry operable to create one or more wavelength channels at each output.

39. The optical processor of claim 38, wherein the control circuitry is further operable to select center wavelength of each of said one or more wavelength channels at each output.

40. The optical processor of claim 39, wherein the control circuitry is further operable to select said center wavelength to align with a desired center wavelength for the wavelength channel.

41. The optical processor of claim 40, wherein each controllable element has an element width, and wherein the control circuitry is further operable to delineate a group of controllable elements for the channel, the processor constructed and arranged such that an input light beam exactly at the desired center wavelength for the channel arrives at the SIM such that the center of the incident light beam is within a half of said width from the center of the delineated group of controllable elements.

42. The optical processor of claim 41, wherein the control circuitry is further operable to dynamically reassign controllable elements to the group for a particular channel.

43. The optical processor of claim 39, wherein the control circuitry is further operable to tune the center wavelength of each of one or more wavelength channels at each output.

44. The optical processor of claim 43, wherein the control circuitry is further operable to adapt said center wavelength towards a desired center wavelength for said channel.

45. The optical processor of claim 39, wherein the control circuitry is further operable to select the passband of each of one or more wavelength channels at each output.

46. The optical processor of claim 38, wherein the control circuitry is further operable to vary the passband of each of one or more wavelength channels at each output.

47. The optical processor of claim 38, wherein the control circuitry is further operable to create a first channel to transfer light between an input and an output, and a second channel to transfer light between said input and said output, wherein the first and second channels have adjacent center wavelengths, thereby forming adjacent channels at said output;

and to select control data to control the transfer of light between said input and said output, of light at wavelengths between the center wavelengths of the adjacent channels.

48. The optical processor of claim 47, further comprising control circuitry operable to apply attenuation to light at wavelengths inside the created channels.

49. The optical processor of claim 48 further comprising control circuitry operable to apply independent attenuation levels for each created channel.

50. The optical processor of claim 47, wherein said control data for said adjacent channels is selected to reduce the wavelength variation in the position of the emerging light at said output.

51. The optical processor of claim 47 wherein said control data for said adjacent channels is selected to control crosstalk in the emerging light at said output.

52. The optical processor of claim 33, wherein the control circuitry is further operable to create a first channel to transfer light between an input and an output, and a second channel to transfer light between said input and said output, wherein the first and second channels have adjacent center wavelengths, thereby forming adjacent channels at said output;

the processor being further constructed and arranged to couple light emerging at said output into a respective optical fiber, and to select control data to control the coupling efficiency into the fundamental mode of the optical fiber of emergent light at wavelengths between the center wavelengths of the adjacent channels.

53. The optical processor of claim 52, wherein the holograms displayed are configured to create a set of diffraction orders in emergent light, and the emergent light includes crosstalk from unwanted diffraction orders.

54. The optical processor of claim 52 wherein said control data for said adjacent channels is selected to control a stitching error between adjacent holograms created by said control data.

55. The optical processor of claim 52 wherein said control data for said adjacent channels is selected to control the extinction of light at wavelengths between the center wavelengths of the adjacent channels.

56. The optical processor of claim 29, further comprising control circuitry operable to predict the spatial distribution by wavelength of incident light across the SLM.

57. The optical processor of claim 29 wherein each hologram is arranged to provide a phase ramp to incident light, and each phase ramp has a length that is spatially varied across the SLM to reduce wavelength variation in the deflection angle.

58. The optical processor of claim 29, further comprising plural inputs and at least one output, and control circuitry operable to select wavelengths appearing at said at least one output from said plural inputs.

59. The optical processor of claim 29, wherein the two-dimensional array of controllable elements is continuous.

60. A method of operating an optical processor having a reflective SLM having an array of controllable elements, a dispersion device and a focussing device, wherein the processor is designed such that light beams from a common point on the dispersion device are spatially separated when incident upon the SLM, and wherein the SLM is configured to display holograms at respective locations of incidence of said light beams to provide emergent beams having controllable directions, the method comprising delineating groups of individual controllable elements;

selecting, from stored control data, control data for each group of controllable elements of the SLM;

generating from the respective selected control data a respective hologram at each group of controllable elements; and

varying the delineation of the groups and/or the selection of control data whereby upon illumination of said groups by respective light beams, respective emergent light beams from the groups are controllable independently of each other.

61. A method of operating an optical processor according to claim 60, comprising selecting control of said light beams from a group comprising:

control of direction, control of power, focussing, aberration compensation, sampling and beam shaping.

62. A method according to claim 60, comprising determining, by means of a control device, selection of the groups, selection of control data and delineation of the group boundaries in response to signals from sensors arranged to provide signals indicative of said emergent beams.

63. A method of controlling input light comprising:

causing said light to become angularly dispersed by a dispersion device;

focussing, by a focussing device, angularly dispersed light from the dispersion device to provide focussed light;

making said focussed light incident upon a reflective SLM, whereby the light is spatially distributed across at least a part of the SLM, wherein the SLM has an array of controllable elements; and

displaying respective holograms at respective locations of incidence of said light to provide emergent light whose direction is controlled by the respective holograms.

64. The method of controlling light of claim 63, wherein the light is spatially distributed by frequency across at least a part of the SLM, wherein the SLM has a two- dimensional array of controllable elements;

and wherein the step of displaying respective holograms comprises displaying the respective holograms using two-dimensional groups of controllable elements selected from said two dimensional array at respective locations of incidence of said light to provide emergent light whose direction is controlled by said respective holograms.

65. The method of claim 64, further comprising delineating a respective group of controllable elements for each chosen location whereby the emergent light is determined by the size, shape or position of said groups.

66. A method of directing light using a reflective SLM, a dispersion device and a focussing device, wherein the reflective SLM has an array of controllable elements and wherein the arrangement is configured such that light from a common point on the dispersion device is spatially distributed over the reflective SLM, the method comprising:

causing the controllable elements to display different holograms at chosen locations whereon light is incident, whereby light from said locations emerges in controllable directions.

67. The method of claim 66, wherein the controllable elements are phase-modulating elements.

68. The method of directing light of claim 66, wherein the reflective SLM has a two-dimensional array of controllable elements and wherein the arrangement is configured such that light from a common point on the dispersion device is spatially distributed over the reflective SLM using the focusing device, wherein the step of causing the controllable elements to display different holograms comprises using two-dimensional groups of controllable elements selected from said two dimensional array at said chosen locations whereon said light is incident, whereby light from said locations emerges in controllable directions.

69. The method of claim 68, wherein the controllable elements are phase-modulating elements.

70. The method of claim 68, further comprising delineating a respective group of controllable elements for each chosen location whereby the light emerging from said locations is determined by the size, shape or position of said groups.

71. A method, using a reflective SLM, a dispersion device and a focussing device, wherein the reflective SLM has an array of controllable elements and wherein the arrangement is configured such that light from a common point on the dispersion device is spatially distributed over the reflective SLM, of measuring at least one spectral property selected from:

channel power, channel centre wavelength, channel bandwidth occupied and noise power between channels, the method comprising causing the controllable elements to display different holograms at chosen locations whereon light is incident, whereby light from said locations emerges in controllable directions to at least one sensor.

72. An optical processor arranged to function as at least one of the following:

an optical add/drop multiplexer, an optical monitoring device, a channel equaliser, a channel controller, a programmable optical source, a programmable optical filter, an optical spectrum analyser, an evaluation device, a reconfigurable wavelength demultiplexer, and a reconfigurable wavelength multiplexer, the processor having a reflective SLM, a dispersion device and a focussing device, wherein the SLM has an array of controllable elements, wherein the processor is configured such that light from a common point on the dispersion device is spatially distributed over the SLM, and wherein the processor is configured such that the controllable elements display different holograms at chosen locations, whereby light from said locations emerges in respective directions, the directions deviating from a direction of specular reflection.

73. A method of operating an optical processor having a reflective SLM having a two-dimensional array of controllable elements, a dispersion device and a focusing device wherein the processor is designed such that light beams from a common point on the dispersion device are spatially separated when incident upon the SLM, and wherein the SLM is configured to display holograms at respective locations of incidence of said light beams to provide emergent beams having controllable directions, the method comprising delineating two-dimensional groups of individual controllable elements;

selecting, from stored control data, control data for each group of controllable elements of the SLM;

generating from the respective selected control data a respective hologram at each group of controllable elements; and

varying one of the delineation of the groups and the selection of control data whereby upon illumination of said groups by respective light beams, respective emergent light beams from the groups are controllable independently of each other.

74. The method of claim 73, further comprising:

selecting control of said light beams from a group comprising;

control of direction, control of power, focusing, aberration compensation, sampling and beam shaping.

75. The method according to claim 73, further comprising:

determining, by means of a control device, selection of the groups, selection of control data and delineation of the group boundaries in response to signals from sensors arranged to provide signals indicative of said emergent beams.

76. An optical processor having a reflective SLM, a dispersion device and a focusing device, wherein the SLM has a two-dimensional array of controllable elements;

wherein the processor is configured such that light from a common point on the dispersion device is spatially distributed over the SLM using the focusing device, and wherein the processor is configured such that the controllable elements display different holograms using two-dimensional groups of controllable elements selected from said two dimensional array at chosen locations, whereby light from said locations emerges in respective directions, the directions deviating from a direction of specular reflection.

77. The optical processor of claim 76 further comprising means for delineating a respective group of controllable elements for each chosen location whereby the light from said locations is determined by the size, shape or position of said groups.

78. The optical processor of claim 76, wherein the optical processor is an optical routing device.

79. The optical processor of claim 76, wherein the optical processor is an optical add/drop multiplexer.

80. The optical processor of claim 76, wherein the optical processor is configured to drop at least one signal from a WDM ensemble.

81. The optical processor of claim 76, wherein the optical processor is configured to add at least one signal to a WDM ensemble.

82. The optical processor of claim 76, wherein the optical processor is an optical monitoring device.

83. The optical processor of claim 76, wherein the optical processor is a channel equalizer.

84. The optical processor of claim 76, wherein the optical processor is a channel controller.

85. The optical processor of claim 76, wherein the optical processor is a programmable optical source.

86. The optical processor of claim 76, wherein the optical processor is a programmable optical filter.

87. The optical processor of claim 76, wherein the optical processor is an optical spectrum analyzer.

88. The optical processor of claim 76, wherein the optical processor is an evaluation device.

89. The optical processor of claim 76, wherein the optical processor is a reconfigurable wavelength demultiplexer.

90. The optical processor of claim 76, wherein the optical processor is a reconfigurable wavelength multiplexer.

91. A method of operating an optical processor having a reflective SLM having a two-dimensional array of controllable elements, a dispersion device and a focusing device wherein the processor is designed such that light beams from a common point on the dispersion device are spatially separated when incident upon the SLM, and wherein the SLM is configured to display holograms at respective locations of incidence of said light beams to provide emergent beams having controllable directions, the method comprising:

delineating two-dimensional groups of individual controllable elements;

selecting, from stored control data, control data for each group of controllable elements of the SLM;

generating from the respective selected control data a respective hologram at each group of controllable elements; and

varying both the delineation of the groups and the selection of control data whereby upon illumination of said groups by respective light beams, respective emergent light beams from the groups are controllable independently of each other.