BI-DIRECTIONAL TRANSMISSION SYSTEM USING SINGLE OPTICAL FIBER

摘要

PURPOSE: A bi-directional transmission system is provided to eliminate the necessity of optical source in a base station, while allowing for a bi-directional transmission through the use of a single optical fiber. CONSTITUTION: A bi-directional transmission system comprises a central office(100) and a base station(200). The central office includes an optical source(110); a polarization controller(120) for controlling polarization of the light emitted from the optical source; a Mach-Zehnder modulator(130) for modulating the optical signal and the downward signal serving as an RF signal; a circulator(140) for transmitting the output of the Mach-Zehnder modulator through the optical fiber; and an optical detector(150) for restoring the upward signal received through the circulator to an RF signal. The base station includes a circulator(210) for receiving signals from the central office and transmitting the upward signal to the central office; a photocoupler(220) for receiving the optical signal from the central office and separating the optical signal at a predetermined ratio; an optical detector(230) for restoring the downward signal input through the photocoupler to an RF signal; a polarization controller(250) for controlling polarization of the light signal excluding the light signal separated by the photocoupler and input to the optical detector; and a Mach-Zehnder modulator(260) for modulating the optical signal and the upward signal serving as an RF signal.