Patent ID: 7596315

Claim:
A wavelength division multiplexing optical transmission system comprising: a plurality of wavelength-variable optical transmitters outputting a plurality of optical transmission signals, respectively, each wavelength-variable optical transmitter having a wavelength-variable light source producing the optical transmission signal output by the respective wavelength-variable optical transmitter; a multiplexer multiplexing the plurality of optical transmission signals and thereby outputting multiplexed optical transmission signals; and a return optical signal generator generating a respective return optical signal corresponding to each optical transmission signal from the multiplexed optical transmission signals output by the multiplexer, and transmitting each respective return optical signal to the respective wavelength-variable optical transmitter that output the respective optical transmission signal to which the respective return signal corresponds, via said multiplexer, and a plurality of ports corresponding respectively to the plurality of wavelength-variable optical transmitters, wherein each wavelength-variable optical transmitter transmits the optical transmission signal output from the respective wavelength-variable optical transmitter through the corresponding port to the multiplexer, and each return optical signal is transmitted from the multiplexer through the port corresponding to the respective wavelength-variable optical transmitter that output the respective optical transmission signal to which the respective return signal corresponds, to the respective wavelength-variable optical transmitter, so that each return optical signal is thereby transmitted through the same port as the optical transmission signal that corresponds to the respective return optical signal, and wherein said each wavelength-variable optical transmitter comprises: a first sensor sensing the return optical signal transmitted to the respective wavelength-variable optical transmitter; and a controller controlling a transmission wavelength of the optical transmission signal produced by the light source of the respective wavelength-variable optical transmitter based on the return optical signal sensed by the first sensor, when the transmission wavelength of the optical transmission signal produced by the light source is set so as to match a port wavelength proper to the input port to which the optical transmission signal output by the respective wavelength-variable optical transmitter is transmitted to thereby enable wavelength multiplexing by the multiplexer.