Patent ID: 7392440

Claim:
An optical signal receiving equipment, comprising: an optical-electrical converting means for converting received optical signals into electronic signals; a plurality of variable-threshold deciders configured to transform the electronic signals into a plurality of first binary signals; a soft decision-identification means for computing identification signals based on results of transformation by the plurality of variable-threshold deciders, and for computing reliability information indicating a level of reliability of the identification signals; an error correction means for correcting an error in the identification signals by using the reliability information computed by the soft decision-identification means; a fixed-threshold decider configured to execute hard-decision identification of the electronic signals, independently from the soft decision-identification means and the plurality of variable-threshold deciders; and a control means for executing the hard decision-identification of the electronic signals by using the fixed-threshold decider, for measuring an average amplitude of the electronic signals based on the hard decision-identification results, and for correcting a plurality of thresholds in the plurality of variable-threshold deciders based on a variation of the measured average amplitude over a time period.