Wavelength division multiplexing light transmitting system

摘要

A wavelength division multiplexing light transmitting system which can monitor its transmission line. One light among the signal lights to be wavelength multiplexed is defined as an optical fibre transmission line monitor light. A transmitter multiplexes and transmits the monitor light with the other signal lights. These lights are attenuated and introduced to the other transmission line at return circuits 12. A receiver branches the returned lights, selects the monitor light and detect a condition of the transmission line by correlation processing. The system extremely improves a SNR and a detection time of the monitor signal.