Patent ID: 7505197

Claim:
An optical transmission system, comprising: a transmission station outputting a WDM light that includes a plurality of reference lights together with a plurality of main signal lights; and a Raman amplifier transmitting the WDM light from the transmission station to a reception station, wherein said Raman amplifier includes: an optical amplification medium; a pumping light source configured to generate a plurality of pumping lights having different wavelengths; an optical device capable of introducing said plurality of pumping lights to said optical amplifying medium; an equalization control section configured to control said pumping light source based on the optical powers of said plurality of reference lights such that the optical powers of said plurality of reference lights are equalized; and an automatic level control section configured to control the optical powers of the pumping lights so that the average optical power of the reference lights is held to a predetermined value, wherein the reference lights have wavelengths configured so that respective Raman gains obtained by said plurality of pumping lights reach peaks.