To equalize the gain of wide-band wavelength division multiplex light so as to improve an S/N ratio.
Laser diode modules 10-1 to 10-8 generate signal light of wavelengths λ1 to λ8 respectively. Optical multiplexes 12 and 14 multiplex light of wavelengths λ1 to λ8 outputted from the modules 10-1 to 10-8 respectively. The output light of the multiplexer 12 is amplified by an optical amplifier 16 which is so designed as to amplify light of a wavelength band of λ1 to λ8 uniformly, and the output light of the multiplexer 14 is amplified by an optical amplifier 18 which is so designed as to amplify light of a wavelength band of λ5 to λ8 uniformly. An optical filter 20 removes light of a wavelength band plunger than λ4 from the optical output of the optical simplifier 16. The gain of the respective wavelengths λ1 to λ4 of the optical amplifier 16 is adjusted so as to compensate for the influence of the optical filter 20 on light of wavelengths λ1 to λ4. The optical multiplexer 22 multiplexes the output light of the optical filter 20 and the optical amplifier 18.
AKIBA SHIGEYUKI
EDAKAWA NOBORU
TAGA HIDENORI
