Abstract: This paper introduces a medium and long-range optical-fiber(cable) communication system which can be used in data tranmission of point-to-point or between two local-area-networks. Using optical-fiber as a transmission media, the system is immune from electromagnetic and nuclear radiation interference,and can be applied to some special environments or places unaccessible by human. While the microcontroller is used in the transmitter and receiver in this system,it makes a feature of simple structure, high reliability, the powerful data processing function and flexible design for baud rate of serial port, and fits in with the need of different transmission rate of serial port. It meets the requirement of the remote-control-and-monitor for medium,longrange signal transmission in civil and military fields. Therefore,it has a great potential in the fature.