Patent ID: 7206510

Claim:
A WDM ring network comprising one center node and a plurality of remote nodes all connected together in ring form via a first optical fiber transmission path and a second optical fiber transmission path, said first optical fiber transmission path being used to transmit continuous-wave lights for upstream signal lights from said center node to each of said remote nodes, said second optical fiber transmission path being used to transmit downstream signal lights from said center node to each of said remote nodes and to transmit upstream signal lights (obtained by modulating continuous-wave lights) from each of said remote nodes to said center node, wherein specific wavelength bandwidths are pre-assigned to each of said remote nodes for said continuous-wave lights (for upstream signal lights) and said downstream signal lights, and the wavelength bandwidths for said continuous-wave lights (for upstream signal lights) and those of said downstream signal lights are alternately set; and wherein each of said remote nodes comprises: first optical splitting means for splitting multi-wavelength light with first wavelength bandwidths transmitted via said first optical fiber transmission path; an optical modulating section that demultiplexes the continuous-wave lights of wavelength channels with the wavelength bandwidths pre-assigned to the remote node in said first wavelength bandwidths from the multi-wavelength light split by said first optical splitting means, modulates lights obtained, and multiplexes modulated lights to generate upstream signal lights; optical coupling means for coupling said upstream signal lights to said second optical fiber transmission path; second optical splitting means for splitting said downstream signal lights transmitted via said second optical fiber transmission path; and an optical receiving section that demultiplexes the signal lights of wavelength channels in the wavelength bandwidth pre-assigned to the remote node from the downstream signal lights split by the second optical splitting means and then receives the lights obtained through demultiplexing.