Patent ID: 6870666

Claim:
A controlling apparatus for controlling an operation of a wavelength division multiplexing optical amplifier to collectively amplify wavelength division multiplexed signal light including a plurality of channel lights of different wavelengths, comprising: optical branching means for branching a portion of said wavelength division multiplexed signal light; optical separating means having a transmission wavelength characteristic which periodically varies corresponding to the wavelength channel intervals of said wavelength division multiplexed signal light, and separating the portion of the wavelength division multiplexed signal light branched by said optical branching means into a signal component including the channel lights of respective wavelengths and noise lights around the channel lights and a noise component including the noise lights existing in wavelength bands between the respective wavelength channel lights; light power measuring means capable of measuring the light power of the signal component separated by said optical separating means; and controlling means for controlling the operation of said wavelength division multiplexing optical amplifier based on the light power of the signal component measured by said light power measuring means.