Patent ID: 6882466

Claim:
An optical amplifier for amplifying wavelength division multiplexed signal light which has respective optical signals of a first wavelength band of a C-band containing a plurality of optical signals with several wavelengths different from each other and a second wavelength band of a L-band containing a plurality of optical signals with several wavelengths different from the wavelengths of the optical signals contained in the first wavelength band, comprising: a C-band optical amplifier to amplify optical signals in the C-band with excitation light; an L-band optical amplifier to amplify optical signals in the L-band with excitation light, the L-band optical amplifier being provided in a parallel arrangement with the C-band optical amplifier; and Raman amplification unit provided in series with the C-band optical amplifier and the L-band optical amplifier, on a pre-stage side, to produce Raman amplification in the L-band, with residual excitation light output from the parallel arrangement of the C-band optical amplifier.