SYSTEM AND METHOD FOR MONITORING OPTICAL REPEATER

摘要

PROBLEM TO BE SOLVED: To eliminate the need for a local oscillator in an optical repeater. SOLUTION: A superposing unit 30 in a terminal station 10 superposes on a signal light a reference signal that the optical repeater 18 requires to generate a carrier for sending a monitor signal to the terminal station 10 and send them out to an optical fiber line 14. A light branching unit 46 of the optical repeater 18 divides and applies the light from the terminal station 10 to a photodetector 50. A BPF 54 extracts a reference signal component from the output of the photodetector 50. A reference regenerating circuit 56 and a frequency divider 60 generate the carrier for the monitor signal from the output of the BPF 54. A monitor signal modulator 64 modulates the output of the frequency divider 60 with the monitor signal from a control circuit 62. An exciting circuit 44 impose intensity modulation on exciting lights to optical amplifiers 40 and 42 according to the output of the modulator 64. A photodetector 32 of the terminal station 10 converts a light inputted from an optical fiber line 16 into an electric signal. A frequency divider 38 divides the frequency of the output of a reference oscillator 20 and outputs a signal of the same frequency with the monitor signal carrier. A monitor signal modulator 36 demodulates the output of the photodetector 32 into the monitor signal with the output of the frequency divider 38.