Optical reception apparatus

摘要

An optical receiver includes a soft-decision deciding unit ( 7 ) for deciding an electric received signal according to a plurality of decision levels to output a multivalued decision signal, a demultiplexing unit ( 5 ) for serial-to-parallel converting the multivalued decision signal to output a multivalued parallel signal, a soft-decision error correction decoding unit ( 8 ) for correcting the multivalued parallel signal based on reliability information to output an error-corrected parallel received signal and decision results indicating the decision of the electric received signal according to the plurality of decision levels, a probability density distribution estimation unit ( 9 ) for estimating probability density distributions based on distributions of the decision results, and a decision level control unit ( 10 ) for controlling the plurality of decision levels based on the probability density distributions, thereby improving the transmission quality.