Optical modulation device and optical modulation method

An optical modulation device comprising:

• a first modulation unit that includes:
• a first modulator that forms a first optical modulation signal by modulating a light based on a first drive signal and a first bias signal;
• a second modulator that forms a second optical modulation signal by modulating a light based on a second drive signal and a second bias signal;
• and a phase shifter that makes a phase difference between the first optical modulation signal and the second optical modulation signal closer to π/2 by shifting a phase of the first optical modulation signal with respect to the second optical modulation signal based on a third bias signal;
• a former that forms an adjustment reference signal based on a synthesized signal synthesizing the first optical modulation signal phase-shifted in the phase shifter and the second optical modulation signal;
• and
• a controller that adjusts amplitudes of the first drive signal and the second drive signal and voltages of the first bias signal, the second bias signal and the third bias signal, based on a gap between a current value of the adjustment reference signal and a target value,
• wherein the controller performs an adjustment in a plurality of adjustment periods and starts a second adjustment period next to a first adjustment period before the gap in the first adjustment period is filled.