Patent ID: 8611760

Claim:
An optical modulation device, comprising: a decision circuit that makes a decision with respect to an input data signal in accordance with a timing of a first clock signal; a first modulator that modulates light output based on the data signal by the decision circuit; a second modulator that modulates the modulated light in accordance with a timing of a second clock signal; and a delay controller that delays the first clock signal within a range of a phase margin of the decision circuit, and delays the second clock signal, thereby controlling a state of a phase difference between the data signal and the second clock signal, and wherein the delay controller comprises: a first phase shifter that delays the first clock signal; a phase detector that acquires a phase difference between the first clock signal that is delayed by the first phase shifter and input to the decision circuit, and the data signal input to the decision circuit; a first controller that controls an amount of delay of the first clock signal caused by the first phase shifter and changes the phase difference acquired by the phase detector within the range of the phase margin; a second phase shifter that delays the second clock signal; and a second controller that controls an amount of delay of the second clock signal caused by the second phase shifter.