Optical communications networks utilizing frequency division multiplexing

Abstract

A frequency division multiplexing (FDM) node used in optical communications networks provides add-drop multiplexing (ADM) functionality between optical high-speed channels and electrical low-speed channels. The FDM node includes a high-speed system and an ADM crosspoint. The high-speed system converts between an optical high-speed channel and its constituent electrical low-speed channels through the use of frequency division multiplexing and preferably also QAM modulation. The ADM crosspoint couples incoming low-speed channels to outgoing low-speed channels, thus implementing the ADM functionality for the FDM node.

What is claimed is:  
     
         1 . A node for use in optical communications networks comprising: 
 a transmitter data path comprising: 
 a plurality of high-speed transmitters, each high-speed transmitter for multiplexing a plurality of low-speed channels into an optical high-speed channel, at least one high-speed transmitter comprising: 
 an FDM multiplexer for FDM multiplexing a plurality of the low-speed channels into an electrical high-speed channel, and  
 an E/O converter coupled to the FDM multiplexer for converting the electrical high-speed channel to one of the optical high-speed channels; and  
 
 a WDM multiplexer optically coupled to the plurality of high-speed transmitters for WDM multiplexing the optical high-speed channels into a multi-wavelength optical channel; and  
   a receive data path comprising: 
 a WDM demultiplexer for WDM demultiplexing a multi-wavelength optical channel into a plurality of optical high-speed channels; and  
 a plurality of high-speed receivers optically coupled to the WDM demultiplexer, each high-speed receiver for demultiplexing one of the optical high-speed channels into a plurality of low-speed electrical channels, at least one high-speed receiver comprising: 
 an O/E converter for converting one of the optical high-speed channels to an electrical high-speed channel; and  
 an FDM demultiplexer coupled to the O/E converter for FDM demultiplexing the electrical high-speed channel into a plurality of the low-speed electrical channels.