Patent ID: 8681419

Claim:
An optical amplifier that amplifies signal light with Raman amplification in the Raman amplification medium, comprising: a light source that supplies pump light into the Raman amplification medium; a first detector that detects input power of the pump light to be input to the Raman amplification medium; a second detector that detects output power of the pump light output from the Raman amplification medium; and a processor operable to: calculate transmission loss of the pump light in the Raman amplification medium by comparing the input power with the output power, and calculate transmission loss of the signal light in the Raman amplification medium based on the transmission loss of pump light corrected based on a wavelength of the signal light and a wavelength of the pump light, wherein the light source superimposes information indicating the input power on the bump light to be supplied into the Raman amplification medium by modulating a driving current to be applied to the bump light, and wherein the processor is operable to calculate the transmission loss of the signal light on a side on which the pump light is output from the Raman amplification medium.