Optical transmitter

An optical transmitter, comprising:

• a minute signal generating unit configured to generate a minute signal;
• a data generating unit configured to generate a plurality of modulating signals;
• a driver configured to amplify the plurality of modulating signals generated by the data generating unit;
• a phase shifter configured to control the phase of at least one signal among the plurality of modulating signals to be input to the driver with adding the minute signal generated by the minute signal generating unit;
• a plurality of optical modulators connected in series to each other, and configured to modulate an optical signal on a basis of each of the modulating signals amplified by the driver;
• an optical coupler configured to branch the optical signal modulated by the optical modulator arranged at a last stage in the series;
• a photodiode configured to detect the optical signal branched by the optical coupler and converts the optical signal into an electric signal;
• a synchronous detection unit configured to generate an error signal on a basis of both a minute signal included in the electric signal converted by the photodiode and the minute signal generated by the minute signal generating unit;
• and
• a phase control unit configured to control an amount of phase control of the phase shifter to minimize the error signal generated by the synchronous detection unit.