OPTICAL COMMUNICATION SYSTEM, OPTICAL TRANSMITTER, AND OPTICAL RECEIVER

摘要

PROBLEM TO BE SOLVED: To reduce a Q penalty due to a frequency off-set by making the frequency of local emission light accord with or approximate the frequency of a transmission light source regardless of its modulation scheme.SOLUTION: An optical communication system includes an optical transmitter and an optical receiver connected with the optical transmitter via a transmission path. The optical transmitter transmits a continuous wave optical signal which enables detection of a beat when it is combined with local emission light at a reception side. The optical receiver detects the optical signal by the local emission light to obtain a beat waveform by digital sampling, performs frequency analysis of digital sampling data with the beat waveform before demodulation to detect a beat frequency, and controls the frequency of the local emission light on the basis of the beat frequency.