Optical receiving apparatus and optical receiving method

摘要

An optical receiving apparatus includes: an A/D converting circuit (10); a received-signal demodulating circuit (11) that demodulates a received digital signal from the A/D converting circuit (10) into an m-bit received signal; a soft-decision-data generating circuit (12) that generates n-bit (n‰¤m) soft-decision data based on the m-bit received signal; and an error correcting circuit (13) that performs error correction based on the n-bit soft-decision data and outputs an error-corrected received signal. The soft-decision-data generating circuit (12) generates soft-decision data of n bits (n=p+1) that corresponds to a determination result according to 2 n -1 soft-decision thresholds, by using an MSB of the m-bit received signal as hard-decision data, and by using, as reliability information, a result of comparison between a plurality of bits (k bits, where k‰¤m) on an MSB side of the m-bit received signal and a fixed threshold, or p bits (p‰¤m-k) selected from (m-k) bits on an LSB side of the m-bit received signal.