PURPOSE: To form an efficient optical communication system by reducing power consumption as the entire system and allowing a master station to identify a slave station when an optional slave station sends a data to the master station.

CONSTITUTION: A detection means 6 detects a reference voltage included in a data from an optional slave station 11, and when the voltage is within a 1st voltage range, the means 6 supplies a signal representing the reception mode receiving the data to a controller 5, and the controller 5 controls a power supply device 4 to send a power voltage to the reception section 2 only. On the other hand, the detection means 6 detects the reference voltage as to which 2nd voltage range in the 2nd voltage ranges equal to number of slave stations belongs to identify the slave station 11. A reference voltage generator 14 of each slave station 11 sends a reference voltage within the 2nd voltage range different from slave stations 11 in the transmission mode. Since power voltage is supplied to the transmission section only in the transmission mode in the master station and supplied to the reception section only in the reception mode, the power consumption as the entire optical communication system is reduced and the slave station being a source is identified in the reception mode.