OPTICAL SPACE TRANSMISSION EQUIPMENT

PURPOSE:To avoid noise in the case of optical space transmission by changing the output power of a semiconductor laser oscillator in accordance with a signal based on noise detection information transmitted from the other party. CONSTITUTION:A noise detection circuit 120 detects the increase of noise at the time of optical space transmission. When a laser output change request signal corresponding to noise increase detection in the noise detection circuit 120 of the device of the other party is transmitted, a laser output change request detection circuit 121 outputs a maser output change request detection flag of a laser diode 113 to a maser output changing circuit 122. This circuit 122 controls an APC circuit 123 to stepwise change the laser optical output power of the laser diode 113. Thus, wavelength absorption noise and optical induced noise are avoided.