Optical repeater monitoring system and a method thereof

An optical repeater monitoring method, comprising:

• a reference signal transmitting step for transmitting a reference signal of a predetermined frequency from a reference signal transmitter to an optical repeater through an optical fiber line;
• a carrier generating step in the optical repeater for generating a carrier, which carries a monitor signal of the optical repeater and has a frequency different from that of the reference signal, out of the reference signal;
• a monitor signal modulating step in the optical repeater for modulating the carrier with the monitor signal;
• a monitor signal transmitting step in the optical repeater for transmitting the modulated wave of the monitor signal obtained by the monitor signal modulating step is transmitted toward a monitor signal receiver;
• a demodulating signal generating step in the monitor signal receiver for generating a demodulating signal having a frequency equal to that of the carrier;
• and
• a monitor signal demodulating step in the monitor signal receiver for demodulating the monitor-signal-modulated signal transferred from the optical repeater with the demodulating signal.

An optical repeater monitoring system, comprising:

• an oscillating source;
• a reference signal transmitter to transmit a reference signal with a predetermined frequency generated from an output of the oscillating source to a first optical fiber;
• an optical repeater having a first photodetector to convert the reference signal from the first optical fiber into an electrical signal, a reference signal extractor to extract a component of the converted reference signal from an output of the first photodetector, a carrier generator to generate a carrier from an output of the reference signal extractor, a monitor signal modulator to modulate the carrier generated by the carrier generator with a monitor signal showing an operating state of the optical repeater, and a transmitter to transmit an output of the monitor signal modulator to a second optical fiber;
• a demodulating signal generator to generate a demodulating signal from the output from the oscillating source, the demodulating signal having a frequency equal to that of the carrier of the monitor signal;
• a second photodetector to photodetect the light on the second optical fiber;
• and
• a monitor signal demodulator to demodulate the monitor signal from outputs of the second photodetector and demodulating signal generator.

An optical repeater monitoring method, comprising:

• transmitting a reference signal of a predetermined frequency from a reference signal transmitter to an optical repeater through an optical fiber line;
• generating a carrier, in the optical repeater, the carrier having a frequency different from that of the reference signal;
• modulating the carrier with an optical repeater monitor signal in the optical repeater;
• transmitting the modulated carrier from the optical repeater toward a monitor signal receiver;
• generating a demodulating signal having a frequency equal to that of the carrier in the monitor signal receiver;
• and
• demodulating the modulated carrier with the demodulating signal in the monitor signal receiver.