Patent ID: 7711218

Claim:
An optical reception apparatus comprising: a branching unit that branches an input optical signal of a multivalue phase modulating format into two; a first route through which one of the optical signals branched by the branching unit propagates; a second route through which the other of the optical signals branched by the branching unit propagates; a first delay interferometer arranged on the first route; a second delay interferometer arranged on the second route; a first photoelectric converter that receives an optical signal output from the first delay interferometer and converts it into an electric signal; a second photoelectric converter that receives an optical signal output from the second delay interferometer and converts it into an electric signal; a multiplexer that multiplexes a signal output from the first photoelectric converter and a signal output from the second photoelectric converter; and an error correction unit that performs error correction processing for a signal output from the multiplexer, wherein the optical reception apparatus further comprises: an error-number detector that detects a number of generated errors in a signal propagating on the first route side and also detects a number of generated errors in a signal propagating on the second route side; an error-number comparator that obtains a difference in a number of generated errors on the first and second route sides detected by the error-number detector; and a controller that controls at least one of the first and second delay interferometers and the first and second photoelectric converters so that the difference in the number of generated errors obtained by the error-number comparator is within a preset tolerance.