Patent ID: 6954304

Claim:
A Raman amplifier amplifying wavelength-multiplexed signal light, comprising: a light source unit generating pumping light to amplify the signal light, the signal light having a plurality of wavelengths within a wavelength band of the signal light, and the pumping light having a plurality of pumping light wavelengths within a wavelength band of the pumping light that overlaps a portion of the wavelength band of the signal light; a transmission path propagating the signal light and the pumping light from the light source unit, and amplifying the signal light; pumping light supplying means for supplying the pumping light to the transmission path; and filter means for narrowing a spread of a spectrum of the pumping light, generated by the light source unit, a portion of the pumping light being within the wavelength band of the signal light, and for outputting the pumping light to the pumping light supplying means, the filter means having a filter characteristic in a direction of wavelength where a peak of a transmission characteristic is located at a center wavelength, with respect to a spectrum of each wavelength of the pumping light, the wavelengths of the signal light being spaced further apart in the vicinity of a position at which a pumping light wavelength is located, and being equally spaced closer together for wavelengths of the signal light not in the vicinity of the position at which a pumping light wavelength is located.