Optical transmitter, optical transmission device, optical transmission/reception system, and optical transmission method

An optical transmission/reception system, comprising:

• an optical transmission device configured to transmit a wavelength-multiplexed optical signal;
• and
• an optical receiver configured to receive the wavelength-multiplexed optical signal, on which to perform digital coherent processing, and restore and output a plurality of client signals,
• wherein the optical transmission device includes:
• a plurality of optical transmitters, each of which including:
• a splitter configured to output a plurality of split signals split from a client signal;
• a plurality of modulators configured to be capable of modulating and outputting a plurality of subcarriers having different wavelengths by using the split signals;
• a multiplexer configured to multiplex the split signal modulated;
• and
• a controller configured to control the modulators and the multiplexer;
• wherein the controller is configured to, if a failure occurs in a first modulator of the modulators, then:
• control the splitter output the split signal, which was outputted to the first modulator, to a second modulator of the modulators, wherein the failure has not occurred in the second modulator;
• raise a bit rate of a first subcarrier outputted from the second modulator;
• and
• shift a wavelength of the first subcarrier, and
• wherein the controller is configured to shift the wavelength of the first subcarrier toward a subcarrier which used to be outputted from the first modulator.

An optical transmission method, using an optical transmitter including a plurality of modulators, the optical transmission method comprising:

• outputting a split signal split from a client signal;
• modulating and outputting a plurality of subcarriers having different wavelengths by using the split signals;
• multiplexing the subcarriers modulated;
• and
• if a failure occurs in a first modulator of the modulators, then:
• outputting the split signal, which was outputted to the first modulator, to a second modulator of the modulators, wherein the failure has not occurred in the second modulator;
• raising a bit rate of a first subcarrier outputted from the second modulator;
• and
• shifting a wavelength of the first subcarrier,
• wherein the shifting the wavelength of the first subcarrier comprises shifting the wavelength of the first subcarrier toward a subcarrier which used to be outputted from the first modulator.