Optical modulation/demodulation method, optical communication system, optical transmitting device and optical receiving device

An optical communication system comprising:

• a transmission circuit configured to
• sum a plurality of binary signals having bit rates that are twice or more integer multiples of a bit rate of a low-speed side and having frequencies synchronized with each other with each amplitude further decreasing as the corresponding bit rate becomes higher,
• generate a modulation signal representing a combination of bits of the plurality of binary signals as an amplitude value, and
• transmit an optical signal amplitude-modulated using the modulation signal;
• and
• a reception circuit configured to
• perform photoelectric conversion of the optical signal transmitted in the transmitting step,
• generate a reception signal corresponding to the modulation signal,
• determine the combination of the bits of the plurality of binary signals by identifying all the amplitude values included in the reception signal using thresholds smaller than the number of the combinations of the bits of the plurality of binary signals by one, and
• identify the bits of the plurality of binary signals summed.

An optical receiving device comprising:

• an optical receiver configured to
• perform photoelectric conversion of an optical signal amplitude-modulated using a modulation signal representing a combination of bits of a plurality of binary signals as an amplitude value by summing a plurality of binary signals having bit rates that are twice or more integer multiples of a bit rate of a low-speed side and having frequencies synchronized with each other with each amplitude further decreasing as the corresponding bit rate becomes higher, and
• generate a reception signal corresponding to a modulation signal;
• and
• a frequency splitter configured to
• determine the combination of the bits of the plurality of binary signals by identifying all the amplitude values included in the reception signal using thresholds smaller than the number of the combinations of the bits of the plurality of binary signals by one and
• identify the bits of the plurality of binary signals summed.