Patent ID: 8078064

Claim:
An optical receiver comprising: an intensity adjuster for adjusting intensity of input signal light to output intensity-adjusted signal light, wherein the input signal light is signal light received from an optical transmitter through an optical transmission line; a local-oscillation light source for generating local-oscillation light, wherein the local-oscillation light source is capable of ON-OFF controlling the local-oscillation light; a combiner for combining the intensity-adjusted signal light and the local-oscillation light to output combined light; a converting section for converting the combined light to an electrical signal; an amplitude measuring section for measuring an amplitude of the electrical signal; and a controller for controlling an intensity-adjusting value of the intensity adjuster so as to make a first amplitude value and a second amplitude value equal to each other, wherein the first amplitude value is an amplitude value of the electrical signal which is obtained at a time when waveform-distortion-free signal light is used which is equivalent to output light of the optical transmitter in a state where the local-oscillation light is turned off and the second amplitude is an amplitude value of the electrical signal which is obtained at a time when the received signal light is used in a state where the local-oscillation light is turned off.