PROBLEM TO BE SOLVED: To provide a multi-wavelength stabilizer having a widened drawing band, a multi-constant-wavelength light source, a light source for wavelength division multiplexing system, and a wavelength discriminating device using the stabilizer. ;SOLUTION: A multi-wavelength stabilizer is constituted of an interferometer 26 which makes incident light rays interfere with each other in the period corresponding to the double of the interval between WDM type wavelengths (ch), and, at the same time, outputs the interference light from two ports by shifting the light by a half period, first and second detecting means 27 and 28 which respectively detect the intensities of the light rays outputted from the first and second ports, and a control means 29 which discriminates whether the channels fixed to a prescribed wavelength is an even number or odd number and, at the same time, outputs a control signal to a laser light source 20 to be controlled, so that the output of the light source 20 may have a prescribed wavelength based on the discriminated results and the outputs of the first and second detecting means 27 and 28.;COPYRIGHT: (C)2000,JPO
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