Optical modulation device and control method in optical modulation device

An optical modulation device comprising:

• a modulation unit that modulates an input light by a drive signal to output an optical signal;
• a drive unit that applies the drive signal based on a data signal to the modulation unit;
• and
• a first bias control unit that performs a bias control to adjust an operating point of a bias voltage of the drive signal such that an optical intensity in a modulation curve of the modulation unit decreases according to a bias voltage value sequentially calculated by the first bias control unit, stops the bias control when the data signal is in a different state different from a predefined state during the bias control and, after the stop of the bias control, restarts the bias control using, as an initial value, a bias voltage value calculated by the first bias control unit before the stop of the bias control.