Patent ID: 8081885

Claim:
An optical communication apparatus receiving a modulated optical signal, the modulated optical signal being generated by modulating an optical signal with a first electrical signal, the first electrical signal being obtained by adding a second electrical signal carrying information to be transmitted and a reference electrical signal with predetermined frequency, the optical communication apparatus comprising: means for generating a local oscillator signal; means for coupling the modulated optical signal and the local oscillator signal; means for converting an output signal from the coupling means to a third electrical signal by optical electrical conversion; means for detecting an amount of fluctuation of the reference electrical signal included in the third electrical signal; and means for compensating the second electrical signal included in the third electrical signal using the amount of fluctuation, wherein the compensating means multiplies the second electrical signal by a signal, of which complex expression is based on an inverse value of the amount of fluctuation, and wherein the amount of fluctuation is based on an amplitude value of the reference electrical signal.