OPTICAL TRANSMISSION SYSTEM AND TRANSMISSION TERMINAL STATION

PROBLEM TO BE SOLVED: To attain the control of a signal wavelength and the automatic control of the power level of each wavelength signal by detecting the spectrum of signal light at a reception terminal station, transmitting it to a transmission terminal station, detecting the spectrum of signal light at the transmission terminal station, detecting the spectrum information from the reception terminal station, comparing the spectrum information on the respective sides of transmission and reception and controlling the level and wavelength of transmission signal light. SOLUTION: A control signal from a fiber 1-2 is received by a control signal receiver 5-2 at a computer 4-2, and the spectrum of signal light from the fiber 1-2 is detected by an optical spectrum analyzer 3-2. The optical spectrum information of the signal light on the side of the reception terminal station received by the control signal receiver 5-2 is compared with the optical spectrum information of the signal light on the side of the transmission terminal station detected by the optical spectrum analyzer 3-2, and the presence/absence of readjustment of pre-emphasis is judged while referring to an existent reference. Further, based on the judged result, in order to perform pre-emphasis control, a signal for controlling the gain of an optical amplifier is outputted.