PURPOSE: To simplify the laying construction of optical fibers between a control station and plural field stations and simultaneously to reduce the cost of a system by decresing the number of optical fibers.

CONSTITUTION: An optical star coupler device 4 is installed between a control station 1 and field stations 61 to 615, and the control station 1 and the optical star coupler device 4 are connected by an optical fiber 3 for signal transmission and an optical fiber 2 for power supply. An optical star coupler 45 for signal inside the device 4 branches/couples signal light transmitted from the control station 1 or the field stations 61 to 615 to the control station 1 or the field stations 61 to 615, and star couplers 41 to 43 for power branche power supply light transmitted from the control station 1 to the field stations 61-615. Further, plural synthesizers 71 to 715 synthesize the signal light and the power supply light respectively branched by both the star couplers 45 and 41 to 43 and transmit it to the respective field stations 61 to 615.