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 channels, 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. An optical add-drop apparatus comprising
 an input port for an input multi-wavelength optical signal having first spectral channels; 
 one or more other ports for second spectral channels; an output port for an output multi-wavelength optical signal; 
 a wavelength-selective device for spatially separating said spectral channels; and 
 a spatial array of beam-deflecting elements positioned such that each element receives a corresponding one of said spectral channels, each of said elements being individually and continuously controllable in two dimensions to reflect its corresponding spectral channel to a selected one of said ports and to control the power of the spectral channel reflected to said selected port. 
 
     
     
       2. The optical add-drop apparatus of  claim 1  further comprising a control unit for controlling each of said beam-deflecting elements. 
     
     
       3. The optical add-drop apparatus of  claim 2 , wherein the control unit further comprises a servo-control assembly, including a spectral monitor for monitoring power levels of selected ones of said spectral channels, and a processing unit responsive to said power levels for controlling said beam-deflecting elements. 
     
     
       4. The optical add-drop apparatus of  claim 3 , wherein said servo-control assembly maintains said power levels at predetermined values. 
     
     
       5. The optical add-drop apparatus of  claim 2 , wherein the control unit controls said beam-deflecting elements to direct selected ones of said first spectral channels to one or more of said second ports to be dropped as second spectral channels from said output multi-wavelength optical signal. 
     
     
       6. The optical add-drop apparatus of  claim 2 , wherein the control unit controls said beam-deflecting elements to direct selected ones of said second spectral channels to said output port to be added to said output multi-wavelength optical signal. 
     
     
       7. The optical add-drop apparatus of  claim 1  further comprising alignment mirrors for adjusting alignment of said input and output multi-wavelength optical signals and said second spectral channels with said wavelength-selective device. 
     
     
       8. The optical add-drop apparatus of  claim 7  further comprising collimators associated with said alignment mirrors, and imaging lenses in a telecentric arrangement with said alignment mirrors and said collimators. 
     
     
       9. The optical add-drop apparatus of  claim 1 , wherein said wavelength selective device further combines selected ones of said spectral channels reflected from said beam-deflecting elements to form said output multi-wavelength optical signal. 
     
     
       10. The optical add-drop apparatus of  claim 1 , wherein said one or more other ports comprise an add port and a drop port for respectively adding second and dropping first spectral channels. 
     
     
       11. The optical add-drop apparatus of  claim 1  further comprising a beam-focuser for focusing said separated spectral channels onto said beam deflecting elements. 
     
     
       12. The optical add-drop apparatus of  claim 1 , wherein said wavelength-selective device comprises a device selected from the group consisting of ruled diffraction gratings, holographic diffraction gratings, echelle gratings, curved diffraction gratings, and dispersing prisms. 
     
     
       13. The optical add-drop apparatus of  claim 1 , wherein said beam-deflecting elements comprise micromachined mirrors. 
     
     
       14. The optical add-drop apparatus of  claim 1 , wherein said beam-deflecting elements comprise reflective membranes. 
     
     
       15. An optical add-drop apparatus, comprising
 an input port for an input multi-wavelength optical signal having multiple spectral channels; 
 an output port for an output multi-wavelength optical signal; 
 one or more drop ports for selected spectral channels dropped from said multi-wavelength optical signal; 
 a wavelength-selective device for spatially separating said multiple spectral channels; and 
 a spatial array of beam-deflecting elements positioned such that each element receives a corresponding one of said spectral channels, each of said elements being individually and continuously controllable in two dimensions to reflect its corresponding spectral channel to a selected one of said ports and to control the power of the spectral channel reflected to said selected port, whereby a subset of said spectral channels is directed to said drop ports. 
 
     
     
       16. An optical add-drop apparatus, comprising
 an input port for an input multi-wavelength optical signal having multiple spectral channels; 
 an output port for an output multi-wavelength optical signal; 
 one or more add ports for selected spectral channels to be added to said output multi-wavelength optical signal; 
 a wavelength-selective device for reflecting said multiple and said selected spectral channels; and 
 a spatial array of beam-deflecting elements positioned such that each element receives a corresponding one of said spectral channels, each of said elements being individually and continuously controllable in two dimensions to reflect its corresponding spectral channel to a selected one of said ports and to control the power of the spectral channel reflected to said selected port, whereby said spectral channels from said add ports are selectively provided to said output port. 
 
     
     
       17. A method of performing dynamic add and drop in a WDM optical network, comprising
 separating an input multi-wavelength optical signal into spectral channels; 
 imaging each of said spectral channels onto a corresponding beam-deflecting element; and 
 controlling dynamically and continuously said beam-deflecting elements in two dimensions so as to combine selected ones of said spectral channels into an output multi-wavelength optical signal and to control the power of the spectral channels combined into said output multi-wavelength optical signal. 
 
     
     
       18. The method of  claim 17 , wherein said selected ones of said spectral channels comprises a subset of said spectral channels, such that other non-selected ones of said spectral channels are dropped from said output multi-wavelength optical signal. 
     
     
       19. The method of  claim 18 , wherein said controlling comprises reflecting said non-selected ones of said spectral channels to one or more drop ports. 
     
     
       20. The method of  claim 17  further comprising imaging other spectral channels onto other corresponding beam-deflecting elements, and controlling dynamically and continuously said other beam-deflecting elements so as to combine said other spectral channels with said selected ones of said spectral channels into said output multi-wavelength optical signal. 
     
     
       21. The method of  claim 17 , wherein said imaging comprises focusing said spectral channels onto said beam-deflecting elements. 
     
     
       22. The method of  claim 17  further comprising monitoring a power level in one or more of said selected ones of said spectral channels, and controlling an alignment between said input multi-wavelength optical signal and corresponding beam-deflecting elements in response to said monitoring.