Patent ID: 8639125

Claim:
A light reception device, comprising: an interferometer configured to output a pair of signals complementing each other obtained by making an optical phase modulated signal interfere with a reference signal after shifting an optical phase of the optical phase modulated signal by a given amount; a pair of light reception elements configured to respectively receive the pair of signals from the interferometer and to respectively convert the pair of signals into a pair of light reception currents; and a phase controller configured to control a control amount so that Iph+A·δIph/δP) or Iph−A·δIph/δP becomes an extreme value or 0, when the Iph represents the difference of the pair of light reception currents of the pair of light reception elements, the δIph/δP represents a change amount of the Iph against the control amount, and the A represents a coefficient to make a maximum amplitude of the Iph equal to a maximum amplitude of the δIph/δP.