WAVELENGTH CONVERSION DEVICE

PURPOSE:To simplify an optical isolator and an optical system by imposing optical intensity modulation upon a frequency-modulated signal which has specific wavelength in a multiplexed converted light group, and making this intensity-modulated light incident on a laser which oscillates with the wavelength of a transmission destination not in the direction of the optical axis of the laser resonator. CONSTITUTION:A wavelength filter 4 whose light output is adjustable with multiplexed different-wavelength wavelenth-converted light beams 1 which have frequency modulated signals converts the frequency-modulated signal light 2. Then the signal is made incident on the flank of the semiconductor laser 5 which oscillates with the target wavelength. The laser intensity is varied with the incident light 2 which varies in incidence intensity and wavelength variation is caused at the same time to cause frequency variation. The optical axis 3-3' of the oscillation laser and the optical axis 2-2' of the incident light are different from each other, so oscillation light beams 3 and 3' are not coupled with the frequency filter 4 by the flank incidence method and the optical isolator is therefore needed. Consequently, the optical system is simplified.