Patent ID: 8831441

Claim:
A optical communication system comprising: an optical transmitter that modulates a plurality of subcarriers orthogonal to each other by mapping digital data to the plurality of subcarriers over a symbol time, and transmits the modulated subcarriers via an optical fiber as optical signals; and an optical receiver that photoelectrically converts the optical signals that are propagated along the optical fiber, decodes the subcarrier signals, and regenerates the original digital signals, wherein the optical transmitter includes: a transmission signal processing unit that modulates a plurality of subcarriers orthogonal to each other by mapping digital data to the plurality of subcarriers over a symbol time, and performs inverse fast Fourier transform on the modulated subcarrier signals to generate a real base-band OFDM signal; and a phase modulator that phase-modulates light from a light source with the real base-band OFDM signal and sends out the phase-modulated light, and the optical receiver includes: a delay interferometer that converts the phase-modulated optical signal that is sent from the optical transmitter via the optical fiber to two intensity-modulated optical signals; two photoelectric converters that convert the two intensity-modulated optical signals to electrical signals; two AD converters that respectively A/D convert the outputs sent from the two photoelectric converters; two phase extraction units that respectively extract phases from the outputs of the two AD converters; two reception signal pre-processing units that respectively perform FFT transform on the outputs of the two phase extraction units, and respectively obtain subcarrier signals; a subtraction unit that calculates the differences between subcarrier signals having the same frequencies about all the subcarrier signals output from the two reception signal pre-processing units; and a reception signal post-processing unit that demodulates the outputs of the subtraction unit in units of respective subcarriers to obtain data, and regenerates the original digital data from the obtained data.