Patent ID: 8564876

Claim:
A Raman amplifier amplifying signal light with the use of a fiber connecting medium, comprising: a pumping unit supplying pumping light to the fiber connecting medium; a noise component estimation unit estimating, from the pumping light amount, a noise component generated in the fiber connecting medium; an extracting unit extracting a predetermined wavelength band including signal light from a received light signal, and causing a wavelength band other than said predetermined wavelength band to branch off; a first monitoring unit detecting a light amount of a received light signal in the predetermined wavelength band extracted by said extracting unit; a second monitoring unit detecting a light amount of the received light signal in the wavelength band other than the predetermined wavelength band having branched off by said extracting unit; a control unit controlling said pumping unit based on the received light amounts detected by said first and second monitoring units and the noise component estimation value obtained by said noise component estimation unit; a first signal light amount calculating unit calculating a signal light amount based on the detection result by said first monitoring unit; a second signal light amount calculating unit calculating a signal light amount by correcting the detection result from said second monitoring unit with the use of the noise component estimation value by said noise component estimation unit; and a correcting unit correcting the noise component estimation value by comparing between respective calculation values by said first signal light amount calculating unit and said second signal light amount calculating unit.