Patent ID: 6891995

Claim:
A wavelength division multiplex transmission system in which optical signals of different wavelengths are transmitted by using a wavelength division multiplex scheme, the system comprising: a transmitting section that uses an electrical-optical converter for generating an optical signal having therein a monitor signal multiplexed with a data signal to be transmitted and having a wavelength chirp due to the monitor signal; a wavelength multiplexer operable to multiplex the optical signal generated by the transmitting section with another optical signal having a wavelength different from a wavelength of the optical signal; an optical transmission path operable to propagate a multiplexed optical signal obtained by the wavelength multiplexer; a wavelength demultiplexer operable to demultiplex the optical signal propagated via the optical transmission path, and obtain the optical signal generated by the transmitting section so as to obtain the data signal; a control signal generator which includes: an optical-electrical converter operable to convert the optical signal after a desired wavelength is extracted based on a transmission characteristic of the wavelength multiplexer or the wavelength demultiplexer to an electrical signal; a filter operable to extract the monitor signal from the electrical signal obtained through conversion by the optical-electrical converter; and a difference detector operable to find a difference between the level of the monitor signal extracted by the filter and a predetermined reference level, and wherein the control signal generator generates a control signal based on the detection results of the difference detector; and a wavelength controller operable to control, based on the control signal, a wavelength of light output from the electrical-optical converter.