Patent ID: 7312918

Claim:
An optical transmission system comprising: an optical transmission line through which a main signal light is propagated having a plurality of optical transmitters, and a plurality of transmission sections, each transmission section being connected to an input side of one optical transmitter of said plurality of optical transmitters, and including: a cutoff section configured to cutoff the main signal light outputted from a preceding optical transmitter and inputted into a Raman amplification medium; a Raman pumping light supply section supplying pumping light to the Raman amplification medium; a monitor section connected to an output side of the Raman amplification medium, and measuring a power of the pumping light supplied by the Raman pumping light supply section to said Raman amplification medium, and a power of Raman amplified light output by the transmission section to the optical transmitter; a control section controlling said Raman pumping light supply section at the time of starting up the system, to vary the power of the pumping light supplied to said Raman amplification medium, controlling said cutoff section depending on the power of said pumping light, and switching the cutoff section between a connection state in which the main signal light propagates through said Raman amplification medium, and a disconnection state in which the main signal light does not propagate through said Raman amplification medium; and a processing section located between the monitoring section and the control section, to detect a power of a noise light generated due to the Raman pumping light, and a power of the main signal light inputted into the optical transmitter based on the power of the pumping light supplied by the Raman pumping light supply section to said Raman amplification medium, and the power of the Raman amplified light output by the transmission section to the optical transmitter measured by said monitor section in the connection and disconnection state of said cutoff section, and the processing section executes a calculation to correct said noise light.