Patent ID: 7444077
Filing Date: 2008-10-28
Classification: H04B,H04J

Abstract:
1. An optical transmission system comprising: an optical signal transmitter to output an optical signal; a monitoring light transmitter to output a monitoring light having a wavelength being different from a wavelength of the optical signal; an optical multiplexer to generate and output a multiplexed signal light by multiplexing the optical signal and the monitoring light; an optical relay transmission path to amplify and transmit the multiplexed signal light with a Raman amplification effect exerted by pumping light output from a pumping light source to be used for distributed Raman amplification; an optical demultiplexer to demultiplex the multiplexed signal light transmitted through said optical relay transmission path for every wavelength and to output the optical signal separated from the monitoring light; an optical signal receiver to receive the optical signal output from said optical demultiplexer; and a pumping light source stopping device to continuously monitor a transmission state of the monitoring light and, when the transmission of the monitoring light is interrupted, to stop emission of the pumping light from said pumping light source to be used for distributed Raman amplification, and the pumping light source stopping device comprises: an optical branching device to optically branch the multiplexed signal light; a monitoring light passing filter to pass the monitoring light included in the branched multiplexed signal light and remove the optical signal components therein; a monitoring light detector to receive passing light having passed through said monitoring light passing filter, and to detect the monitoring light by demodulating the received passing light into the electrical monitoring signal; and a controller to turn off said pumping light source when the monitoring light is not detected.