Patent ID: 7936998

Claim:
An optical transmitter apparatus, comprising: a phase modulator, having a first phase modulation element for generating a first modulation signal on a first arm in accordance with a first driving signal, a second phase modulation element for generating a second modulation signal on a second arm in accordance with a second driving signal, and a phase shift element for providing a phase difference between the first arm and the second arm, which generates a phase-modulated signal by combining the first and second modulation signals; a DC bias generator unit for generating first DC bias and second DC bias for adjusting an operation point of the first and second phase modulation elements; an intensity modulator for performing intensity modulation on the phase-modulated signal output from said phase modulator; a detection unit for detecting the power of an AC component of an optical signal output from said intensity modulator; and an adjuster unit for adjusting an amount of phase shift of the phase shift element as well as adjusting at least one of the first bias or the second bias based on the power detected by said detection unit.