Patent ID: 6999230

Claim:
An apparatus for receiving wavelength division multiplexed light from a first optical transmission apparatus and for transmitting the wavelength-division-multiplexed light to a second optical transmission apparatus, comprising: an optical amplifier for amplifying the wavelength-division-multiplexed light; an excitation light source for supplying excitation light; a multiplexing section for inputting excitation light from the excitation light source into the optical amplifier; a monitor unit for observing light intensity of signal light and four wave mixing (FWM) light included in the wavelength-division-multiplexed light from the optical amplifier; an arithmetic unit for calculating a difference in light intensity between the signal light and the FWM light as a calculated FWM crosstalk value; and a control unit for sending the calculated FWM crosstalk value to the first optical transmission apparatus, and for controlling an intensity of the excitation light according to a calculated FWM crosstalk value received from the second optical transmission apparatus so that the received calculated FWM crosstalk value becomes a predetermined target value or below.