Reconfigurable optical add-drop multiplexers with servo control and dynamic spectral power management capabilities

Abstract

This invention provides a novel wavelength-separating-routing (WSR) apparatus that uses a diffraction grating to separate a multi-wavelength optical signal by wavelength into multiple spectral characters, which are then focused onto an array of corresponding channel micromirrors. The channel micromirrors are individually controllable and continuously pivotable to reflect the spectral channels into selected output ports. As such, the inventive WSR apparatus is capable of routing the spectral channels on a channel-by-channel basis and coupling any spectral channel into any one of the output ports. The WSR apparatus of the present invention may be further equipped with servo-control and spectral power-management capabilities, thereby maintaining the coupling efficiencies of the spectral channels into the output ports at desired values. The WSR apparatus of the present invention can be used to construct a novel class of dynamically reconfigurable optical add-drop multiplexers (OADMs) for WDM optical networking applications.

What is claimed is:  
     
       1. A wavelength-separating-routing apparatus, comprising:
 a) multiple fiber collimators, providing an input port for a multi-wavelength optical signal and a plurality of output ports;  
 b) a wavelength-separator, for separating said multi-wavelength optical signal from said input port into multiple spectral channels;  
 c) a beam-focuser, for focusing said spectral channels into corresponding spectral spots; and  
 d) a spatial array of channel micromirrors positioned such that each channel micromirror receives one of said spectral channels, said channel micromirrors being individually and continuously controllable to reflect said spectral channels into selected ones of said output ports.  
 
     
     
       2. The wavelength-separating-routing apparatus of  claim 1  further comprising a servo-control assembly, in communication with said channel micromirrors and said output ports, for providing control of said channel micromirrors and thereby maintaining a predetermined coupling of each reflected spectral channel into one of said output ports. 
     
     
       3. The wavelength-separating-routing apparatus of  claim 2  wherein said servo-control assembly comprises a spectral monitor for monitoring power levels of said spectral channels coupled into said output ports, and a processing unit responsive to said power levels for providing control of said channel micromirrors. 
     
     
       4. The wavelength-separating-routing apparatus of  claim 3  wherein said servo-control assembly maintains said power levels at a predetermined value. 
     
     
       5. The wavelength-separating-routing apparatus of  claim 1  further comprising an array of collimator-alignment mirrors, in optical communication with said wavelength-separator and said fiber collimators, for adjusting an alignment of said multi-wavelength optical signal from said input port and directing said reflected spectral channels into said output ports. 
     
     
       6. The wavelength-separating-routing apparatus of  claim 5  wherein each collimator-alignment mirror is rotatable about one axis. 
     
     
       7. The wavelength-separating-routing apparatus of  claim 5  wherein each collimator-alignment mirror is rotatable about two axes. 
     
     
       8. The wavelength-separating-routing apparatus of  claim 5  further comprising first and second arrays of imaging lenses, in a telecentric arrangement with said collimator-alignment mirrors and said fiber collimators. 
     
     
       9. The wavelength-separating-routing apparatus of  claim 1  wherein each channel micromirror is continuously pivotable about one axis. 
     
     
       10. The wavelength-separating-routing apparatus of  claim 1  wherein each channel micromirror is pivotable about two axes. 
     
     
       11. The wavelength-separating-routing apparatus of  claim 10  wherein said fiber collimators are arranged in a two-dimensional array. 
     
     
       12. The wavelength-separating-routing apparatus of  claim 1  wherein each channel micromirror is a silicon micromachined mirror. 
     
     
       13. The wavelength-separating-routing apparatus of  claim 1  wherein said fiber collimators are arranged in a one-dimensional array. 
     
     
       14. The wavelength-separating-routing apparatus of  claim 1  wherein said beam-focuser comprises a focusing lens having first and second focal points. 
     
     
       15. The wavelength-separating-routing apparatus of  claim 14  wherein said wavelength-separator and said channel micromirrors are placed respectively at said first and second focal points of said focusing lens. 
     
     
       16. The wavelength-separating-routing apparatus of  claim 1  wherein said beam-focuser comprises an assembly of lenses. 
     
     
       17. The wavelength-separating-routing apparatus of  claim 1  wherein said wavelength-separator comprises an element selected from the group consisting of ruled diffraction gratings, halographic diffraction gratings, echelle gratings, curved diffraction gratings, and dispersing gratings. 
     
     
       18. The wavelength-separating-routing apparatus of  claim 1  further comprising a quarter-wave plate optically interposed between said wavelength-separator and said channel micromirrors. 
     
     
       19. The wavelength-separating-routing apparatus of  claim 1  wherein each output port carries a single one of said spectral channels. 
     
     
       20. The wavelength-separating-routing apparatus of  claim 19  further comprising one or more optical sensors, optically coupled to said output ports. 
     
     
       21. A servo-based optical apparatus comprising:
 a) multiple fiber collimators, providing an input port for a multi-wavelength optical signal and a plurality of output ports;  
 b) a wavelength-separator, for separating said multi-wavelength optical signal from said input port into multiple spectral channels;  
 c) a beam-focuser, for focusing said spectral channels into corresponding spectral spots; and  
 d) a spatial array of channel micromirrors positioned such that each channel micromirror receives one of said spectral channels, said channel micromirrors being individually controllable to reflect said spectral channels into selected ones of said output ports; and  
 e) a servo-control assembly, in communication with said channel micromirrors and said output ports, for maintaining a predetermined coupling of each reflected spectral channel into one of said output ports.  
 
     
     
       22. The servo-based optical apparatus of  claim 21  wherein said servo-control assembly comprises a spectral monitor for monitoring power levels of said spectral channels coupled into said output ports, and a processing unit responsive to said power levels for providing control of said channel micromirrors. 
     
     
       23. The servo-based optical apparatus of  claim 22  wherein said servo-control assembly maintains said power levels at a predetermined value. 
     
     
       24. The servo-based optical apparatus of  claim 21  further comprising an array of collimator-alignment mirrors, in optical communication with said wavelength-separator and said fiber collimators, for adjusting an alignment of said multi-wavelength optical signal from said input port and directing said reflected spectral channels into said output ports. 
     
     
       25. The servo-based optical apparatus of  claim 24  further comprising first and second arrays of imaging lenses, in a telecentric arrangement with said collimator-alignment mirrors and said fiber collimators. 
     
     
       26. The servo-based optical apparatus of  claim 24  wherein each collimator-alignment mirror is rotatable about at least one axis. 
     
     
       27. The servo-based optical apparatus of  claim 21  wherein each channel micromirror is continuously pivotable about at least one axis. 
     
     
       28. The servo-based optical apparatus of  claim 21  wherein each channel micromirror is a silicon micromachined mirror. 
     
     
       29. The servo-based optical apparatus of  claim 21  wherein said wavelength-separator comprises an element selected from the group consisting of ruled diffraction gratings, holographic diffraction gratings, echelle gratings, curved diffraction gratings, and dispersing prisms. 
     
     
       30. The servo-based optical apparatus of  claim 21  wherein said beam-focuser comprises one or more lenses. 
     
     
       31. An optical apparatus comprising:
 a) an array of fiber collimators, providing an input port for a multi-wavelength optical signal and a plurality of output ports;  
 b) a wavelength-separator, for separating said multi-wavelength optical signal from said input port into multiple spectral channels;  
 c) a beam-focuser, for focusing said spectral channels into corresponding spectral spots;  
 d) a spatial array of channel micromirrors positioned such that each channel micromirror receives one of said spectral channels, said channel micromirrors being individually and continuously controllable to reflect said spectral channels into selected ones of said output ports; and  
 e) a one-dimensional array of collimator-alignment mirrors, for adjusting an alignment of said multi-wavelength optical signal from said input port and directing said reflected spectral channels into said output ports.  
 
     
     
       32. The optical apparatus of  claim 31  further comprising a servo-control assembly, in communication with said channel micromirrors, said collimator-alignment mirrors, and said output ports, for providing control of said channel micromirrors along with said collimator-alignment mirrors and thereby maintaining a predetermined coupling of each reflected spectral channel into one of said output ports. 
     
     
       33. The optical apparatus of  claim 32  wherein said servo-control assembly comprises a spectral monitor for monitoring power levels of said spectral channels coupled into said output ports, and a processing unit responsive to said power levels for providing control of said channel micromirrors and said collimator-alignment mirrors. 
     
     
       34. The optical apparatus of  claim 31  wherein each channel micromirror is continuously pivotable about at least one axis. 
     
     
       35. The optical apparatus of  claim 31  wherein each collimator-alignment mirror is rotatable about at least one axis. 
     
     
       36. The optical apparatus of  claim 31  further comprising first and second arrays of imaging lenses, in a telecentric arrangement with said collimator-alignment mirrors and said fiber collimators. 
     
     
       37. An optical apparatus comprising:
 a) an array of fiber collimators, providing an input port for a multi-wavelength optical signal and a plurality of output ports;  
 b) a wavelength-separator, for separating said multi-wavelength optical signal from said input port into multiple spectral channels;  
 c) a beam-focuser, for focusing said spectral channels into corresponding spectral spots;  
 d) a spatial array of channel micromirrors positioned such that each channel micromirror receives one of said spectral channels, said channel micromirrors being individually and continuously controllable to reflect said spectral channels into selected ones of said output ports; and  
 e) a two-dimensional array of collimator-alignment mirrors, for adjusting an alignment of said multi-wavelength optical signal from said input port and directing said reflected spectral channels into said output ports.  
 
     
     
       38. The optical apparatus of  claim 37  further comprising a servo-control assembly, in communication with said channel micromirrors, and collimator-alignment mirrors, and said output ports, for providing control of said channel micromirrors along with said collimator-alignment mirrors and thereby maintaining a predetermined coupling of each reflected spectral channel into one of said output ports. 
     
     
       39. The optical apparatus of  claim 38  wherein said servo-control assembly comprises a spectral monitor for monitoring power levels of said spectral channels coupled into said output ports, and a processing unit responsive to said power levels for providing control of said channel micromirrors and said collimator-alignment mirrors. 
     
     
       40. The optical apparatus of  claim 37  wherein each collimator-alignment mirror is rotatable about at least one axis. 
     
     
       41. The optical apparatus of  claim 37  wherein each channel micromirror is continuously pivotable about at least one axis. 
     
     
       42. The optical apparatus of  claim 41  wherein each channel micromirrors is pivotable about two axes, and wherein said fiber collimators are arranged in a two-dimensional array. 
     
     
       43. The optical apparatus of  claim 37  further comprising first and second arrays of imaging lenses, in a telecentric arrangement with said collimator-alignment mirrors and said fiber collimators. 
     
     
       44. An optical system comprising a wavelength-separating-routing apparatus, wherein said wavelength-separating-routing apparatus includes:
 a) an array of fiber collimators, providing an input port for a multi-wavelength optical signal and a plurality of output ports including a pass-through port and one or more drop ports;  
 b) a wavelength-separator, for separating said multi-wavelength optical signal from said input port into multiple spectral channels;  
 c) a beam-focuser, for focusing said spectral channels into corresponding spectral spots; and  
 d) a spatial array of channel micromirrors positioned such that each channel micromirror receives one of said spectral channels, said channel micromirrors being individually and continuously pivotable to reflect said spectral channels into selected ones of said output ports, whereby said pass-through port receives a subset of said spectral channels.  
 
     
     
       45. The optical system of  claim 44  further comprising a servo-control assembly, in communication with said channel micromirrors and said output ports, for providing control of said channel micromirrors and thereby maintaining a predetermined coupling of each reflected spectral channel into one of said output ports. 
     
     
       46. The optical system of  claim 45  wherein said servo-control assembly comprises a spectral monitor for monitoring power levels of said spectral channels coupled into said output ports, and a processing unit responsive to said power levels for providing control of said channel micromirrors. 
     
     
       47. The optical system of  claim 44  further comprising an array of collimator-alignment mirrors, in optical communication with said wavelength-separator and said fiber collimators, for adjusting an alignment of said multi-wavelength optical signal from said input port and directing said reflected spectral channels into said output ports. 
     
     
       48. The optical system of  claim 47  further comprising first and second arrays of imaging lenses, in a telecentric arrangement with said collimator-alignment mirrors and said fiber collimators. 
     
     
       49. The optical system of  claim 47  wherein each collimator-alignment mirror is rotatable about at least one axis. 
     
     
       50. The optical system of  claim 44  wherein each channel micromirror is pivotable about at least one axis. 
     
     
       51. The optical system of  claim 44  wherein each channel micromirror is a silicon micromachined mirror. 
     
     
       52. The optical system of  claim 44  wherein said beam-focuser comprises a focusing lens having first and second focal points, and wherein said wavelength-separator and said channel micromirrors are placed respectively at said first and second focal points. 
     
     
       53. The optical system of  claim 44  wherein said wavelength-separator comprises an element selected from the group consisting of ruled diffraction gratings, holographic diffraction gratings, echelle gratings, curved diffraction gratings, and dispersing prisms. 
     
     
       54. The optical system of  claim 44  further comprising a quarter-wave plate optically interposed between said wavelength-separator and said channel micromirrors. 
     
     
       55. The optical system of  claim 44  further comprising an auxiliary wavelength-separating-routing apparatus, including:
 a) multiple auxiliary fiber collimators, providing a plurality of auxiliary input ports and an exiting port;  
 b) an auxiliary wavelength-separator;  
 c) an auxiliary beam-focuser; and  
 d) a spatial array of auxiliary channel micromirrors;  
 wherein said subset of said spectral channels in said pass-through port and one or more add spectral channels are directed into said auxiliary input ports, and multiplexed into an output optical signal directed into said exiting port by way of said auxiliary wavelength-separator, said auxiliary beam-focuser and said auxiliary channel micromirrors.  
 
     
     
       56. The optical system of  claim 55  wherein said auxiliary channel micromirrors are individually pivotable. 
     
     
       57. The optical system of  claim 55  wherein each auxiliary channel micromirror is pivotable continuously about at least one axis. 
     
     
       58. The optical system of  claim 55  wherein each auxiliary channel micromirror is a silicon micromachined mirror. 
     
     
       59. The optical system of  claim 55  wherein said auxiliary wavelength-separator comprises an element selected from the group consisting of ruled diffraction gratings, holographic diffraction gratings, echelle gratings, curved diffraction gratings, and dispersing prisms. 
     
     
       60. The optical system of  claim 55  wherein said pass-through port constitutes one of said auxiliary input ports. 
     
     
       61. A method of performing dynamic wavelength separating and routing, comprising:
 a) receiving a multi-wavelength optical signal from an input port;  
 b) separating said multi-wavelength optical signal into multiple spectral channels;  
 c) focusing said spectral channels onto a spatial array of corresponding beam-deflecting elements, whereby each beam-deflecting element receives one of said spectral channels; and  
 d) dynamically and continuously controlling said beam-deflecting elements, thereby directing said spectral channels into a plurality of output ports.  
 
     
     
       62. The method of  claim 61  further comprising the step of providing feedback control of said beam-deflecting elements, thereby maintaining a predetermining coupling of each spectral channel directed into one of said output ports. 
     
     
       63. The method of  claim 62  further comprising the step of maintaining power levels of said spectral channels directed into said output ports at a predetermining value. 
     
     
       64. The method of  claim 61  wherein each spectral channel is directed into a separate output port. 
     
     
       65. The method of  claim 61  wherein a subset of said spectral channels is directed into one of said output ports, thereby providing one or more pass-through spectral channels. 
     
     
       66. The method of  claim 65  further comprising the step of multiplexing said pass-through spectral channels with one or more add spectral channels, so as to provide an output optical signal. 
     
     
       67. The method of  claim 61  wherein said beam-deflecting elements comprise an array of silicon micromachined mirrors.