Patent ID: 7242519

Claim:
A Raman amplifier for supplying pumping lights to an amplification medium through which is propagated a wavelength division multiplexed signal light obtained by multiplexing a plurality of signal lights of different wavelengths, to amplify the wavelength division multiplexed signal light due to a Raman effect, comprising: a first pumping light generating section that generates a plurality of pumping lights arranged at equal wavelength spacing in a first wavelength band which is shifted from a signal light wavelength band where said plurality of signal lights are arranged to a shorter wavelength side in accordance with the wavelength width corresponding to a Raman shift frequency; a second pumping light generating section that generates pumping lights of one or more wavelengths arranged in a second wavelength band on at least one of a shorter wavelength side and a longer wavelength side than the first wavelength band, the wavelength and power of which are set so that peak wavelength spacing of a Raman gain in the signal light wavelength band is substantially equal to each other; and a multiplexing section that multiplexes the pumping lights generated respectively by said first and second pumping light generating sections to supply the multiplexed pumping light to said amplification medium.