Patent ID: 8693887

Claim:
An optical transmitter that comprises: a light source; a phase modulator into which a light output from said light source is input; a first drive circuit that drives said phase modulator according to a data signal; an intensity modulator into which the light whose phase is modulated by said phase modulator is input, and said intensity modulator has photoelectric response characteristics that change periodically; and a second drive circuit that drives said intensity modulator in accordance with a clock signal having a frequency corresponding to a bit rate of said data signal, and said optical transmitter outputs an optical signal of a phase modulation format, pulse carved by said intensity modulator, wherein there is provided a waveform transformation circuit that varies a duty cycle of said clock signal while keeping an amplitude of said clock signal constant, and said second drive circuit drives said intensity modulator in accordance with a clock signal in which the duty cycle is changed to a different value from 50% and the amplitude is the same as said clock signal by said waveform transformation circuit, with the operating range being a slope from a trough to a crest in the photoelectric response characteristics of said intensity modulator.