OPTICAL SPACE TRANSMITTER

PURPOSE:To finely compensate the temperature of avalanche photo diode with high accuracy corresponding to the dispersion of elements by controlling the output signal level of the avalanche photo bode to be constant based on the temperature detection data and signal level detection data while referring to the characteristic data of the avalanche photo diode. CONSTITUTION:In a system control circuit 30, the temperature of an avalanche photo diode 16 is detected by a thermosensitive element 48 consisting of thermisters and the terminal voltage of the thermosensitive element 48 is inputted to the circuit 30 through an analog/digital conversion circuit 50. Thus, the temperature characteristic of the photo diode 16 is compensated. Further, at the time of compensating the temperature characteristic, the system control circuit 30 switches the control voltage based on the characteristic data previously registered in a memory circuit 46, thereby finely controlling the driving voltage of the photo diode 16 with high accuracy.