Patent ID: 8054455

Claim:
An optical amplifier for amplifying a signal light by supplying a pumping light generated in a pumping light source to an optical amplification medium, comprising: a connecting loss measuring device that inputs a measuring light, which is different from the signal light, to the optical path between said pumping light source and said optical amplification medium, and based on a reflected light and a backward scattering light of the measuring light, which are generated in said optical path, measures connecting losses at one or more connecting points existing on said optical path; and a controller that controls the supply condition of the pumping lights by said pumping light source, according to the connecting losses measured by said connecting loss measuring device, wherein said pumping light source generates pumping lights capable of amplifying due to a Raman effect the signal light being propagated through said optical amplification medium, to supply said pumping lights to said optical amplification medium.