Patent ID: 8891959

Claim:
An optical modulation device, comprising: a generating circuit that generates a low-frequency signal, an average value of amplitude as an alternating-current component of the low-frequency signal being different from a center value of the amplitude of the low-frequency signal; a superimposing unit that superimposes the low-frequency signal on a data signal; an optical modulator that modulates, using the superimposition of the low-frequency signal by the superimposing unit, light from a light source and outputs a light signal; a calculating circuit that calculates an amplitude average value and an amplitude center value of a low-frequency component obtained from the light signal output by the optical modulator, when the amplitude average value and the amplitude center value are different; and a controller that controls a bias voltage of the optical modulator such that the amplitude average value is brought closer to the amplitude center value of the frequency component calculated by the calculating circuit.