Patent ID: 7330302

Claim:
An optical transmission system comprising: a transmitter outputting signal light in which an optical frequency spacing between the adjacent ones of a plurality of signal channels is 400 GHz or more but 12.5 THz or less; an optical fiber transmission line transmitting the signal light; an optical fiber for Raman amplification constituting at least part of said optical fiber transmission line; and Stimulated-Raman-Scattering means which Raman-amplifies the signal light in said optical fiber for Raman amplification, by supplying Raman amplification pumping light, wherein said Stimulated-Raman-Scattering means includes a pumping light source outputting the Raman amplification pumping light which includes a plurality of pumping channels, the plurality of pumping channels having wavelengths different from those of the plurality of signal channels, at least a part of the plurality of pumping channels being located between predetermined Raman gain peaks.