Patent ID: 7142782

Claim:
A noise light elimination method comprising: amplifying a signal light by an optical amplifying section so that a power of signal light components in the amplified signal light exceeds a threshold value, and a power of noise light components in the amplified signal light is smaller than the threshold value; applying the amplified signal light to a stimulated Brillouin scattering generating medium that generates a return light due to stimulated Brillouin scattering when a light having a power exceeding the threshold value is applied; and extracting the return light generated by the stimulated Brillouin scattering generating medium as the amplified signal light, to thereby eliminate the noise light components in the amplified signal light; wherein output light power of said optical amplifying section is set based on said threshold value and insertion loss of optical parts arranged between an output end of said optical amplifying section, and an input end of the stimulated Brillouin scattering generating medium, and wherein said threshold value is variably set in accordance with the stimulated Brillouin scattering generating medium, and said output light power is set at a level exceeding a sum of said threshold value and the value of the insertion loss of the optical parts arranged between the output end of said optical amplifying section and the input end of the stimulated Brillouin scattering generating medium.