Patent ID: 7933063

Claim:
An apparatus for monitoring noise light generated due to Raman amplification, in an optical communication system that supplies pump light to an amplifying medium on a transmission line, and Raman amplifies a main signal light propagating through the amplifying medium and transmits this, the apparatus comprising: a first monitor section that acquires light propagating in an opposite direction with respect to a propagation direction of the main signal light, in the vicinity of a main signal light input end of the amplifying medium, and monitors a power thereof; a second monitor section that acquires light propagating in a same direction with respect to a propagation direction of main the signal light, in the vicinity of a main signal light output end of the amplifying medium, and monitors a power thereof; and an arithmetic processing section that, based on the optical power respectively monitored in the first and second monitor sections, in a condition where the pump light is supplied to the amplifying medium at a time of initial startup of the optical communication system, obtains a relationship for the noise light generated due to Raman amplification, between a power of the forward direction noise light propagating in a same direction with respect to a propagation direction of the main signal light, and a power of the backward direction noise light propagating in an opposite direction with respect to the propagation direction of the main signal light, and during operation of the main signal light in the optical communication system, converts the backward direction noise light power monitored by the first monitor section into the forward direction noise light power in accordance with the relationship obtained at the time of the initial startup.