Subchannel Photonic Routing, Switching and Protection with Simplified Upgrades of WDM Optical Networks

Abstract

The present invention includes novel techniques, apparatus, and systems for optical WDM communications. Tunable lasers are employed to generate respective subcarrier frequencies which represent subchannels of an ITU channel to which client signals can be mapped. In one embodiment, subchannels are polarization interleaved to reduce crosstalk. In another embodiment, polarization multiplexing is used to increase the spectral density. Client circuits can be divided and combined with one another before being mapped, independent of one another, to individual subchannels within and across ITU channels. A crosspoint switch can be used to control the client to subchannel mapping, thereby enabling subchannel protection switching and hitless wavelength switching. Network architectures and subchannel transponders, muxponders and crossponders are disclosed, and techniques are employed (at the subchannel level/layer), to facilitate the desired optical routing, switching, concatenation and protection of the client circuits mapped to these subchannels across the nodes of a WDM network.

What is claimed is: 
     
         1 . A system for adding polarization-multiplexed signals while maintaining orthogonality of polarizations at a node of an optical network, the system comprising:
 (a) a polarization recovery module that recovers the orthogonally polarized states of a plurality of incoming signals; and   (b) a polarization-maintaining add coupler that aligns and matches the orthogonally polarized states of a plurality of added signals with the recovered polarization states of the incoming signals.   
     
     
         2 . The system of  claim 1 , wherein linear orthogonal polarizations are employed. 
     
     
         3 . The system of  claim 1 , further comprising polarization-maintaining components to facilitate polarization recovery and alignment. 
     
     
         4 . A system for dropping polarization-multiplexed signals while demultiplexing orthogonal polarizations at a node of an optical network, the system comprising:
 (a) a polarization recovery module in the node that recovers the orthogonally polarized states of a plurality of incoming signals; and   (b) a polarization-maintaining drop coupler that demultiplexes the orthogonally polarized states of each incoming signal into two distinct signals that are dropped at the node.   
     
     
         5 . The system of  claim 4 , wherein linear orthogonal polarizations are employed. 
     
     
         6 . The system of  claim 4 , further comprising polarization-maintaining components to facilitate polarization recovery and demultiplexing. 
     
     
         7 . A method for adding polarization-multiplexed signals while maintaining orthogonality of polarization at a node of an optical network, comprising the following steps:
 (a) recovering the orthogonally polarized states of a plurality of incoming signals; and   (b) aligning and matching the orthogonally polarized states of a plurality of added signals with the recovered polarization states of the incoming signals.   
     
     
         8 . The method of  claim 7 , wherein linear orthogonal polarizations are employed. 
     
     
         9 . The method of  claim 7 , wherein polarization-maintaining components are employed to facilitate polarization recovery and alignment. 
     
     
         10 . A method for dropping polarization-multiplexed signals while demultiplexing orthogonal polarizations at a node of an optical network, comprising the following steps:
 (a) recovering the orthogonally polarized states of a plurality of incoming signals; and   (b) demultiplexing the orthogonally polarized states of each incoming signal into two distinct signals that are dropped at the node.   
     
     
         11 . The method of  claim 10 , wherein linear orthogonal polarizations are employed. 
     
     
         12 . The method of  claim 10 , wherein polarization-maintaining components are employed to facilitate polarization recovery and demultiplexing.