Patent ID: 7773283

Claim:
An optical modulation device configured to operate under a plurality of modulation formats, comprising: a driving unit adapted to input a modulating signal and for providing a driving signal having a voltage; a Mach-Zehnder modulator electrically connected to the driving unit, adapted to modulate inputted light in accordance with the driving signal from the driving unit, and adapted to output a modulated signal light; an oscillator adapted to oscillate a predetermined frequency signal; a bias controlling unit electrically connected to the Mach-Zehnder modulator and adapted to provide a bias voltage to the Mach-Zehnder modulator in accordance with a frequency component of the predetermined frequency signal in the modulated signal light from the Mach-Zehnder modulator; a switch adapted to input the predetermined frequency signal from the oscillator, the switch changing an output destination of the predetermined frequency signal to the driving unit or the bias controlling unit; and a controller configured to receive an external input designating one of the modulation formats, and to control paths of the switch and the voltage of the driving signal in accordance with the modulation format designated by the external input.