To utilize a supervisory light for gain control of wavelength multiplex signal lights in a wavelength multiplex transmission system provided with a supervisory information transfer means.
The wavelength multiplex transmission system includes an optical transmitter, an optical repeater, and an optical receiver. The optical transmitter and the optical repeater include a supervisory light transmitter for generating the supervisory light which can be amplified by an optical amplifier and has a wavelength different from a main signal. The output side of the device includes a means for multiplexing the wavelength multiplex signal light and the supervisory light, and the optical repeater and the optical receiver include a means for demultiplexing the wavelength multiplex signal light and the supervisory light at the input side of the devices to re-multiplex a part of the supervisory light as the wavelength multiplex signal light. The output side of the optical amplifier includes a means for extracting the supervisory light to detect a light intensity, and a control circuit for controlling a gain of the optical amplifier is provided to control the detected supervisory light intensity at a constant level.
OGAWA KENICHI
NODA KENTA
