SIGNAL PROCESSING DEVICE AND SIGNAL PROCESSING METHOD

摘要

A signal processing means, comprising: a carrier compensation means that generates two carrier compensation signals for two polarization signals, by compensating for phase difference and frequency difference between signal light and local light; a symbol determination means that demodulates the two carrier compensation signals according to a signal arrangement for multi-level modulation; a symbol rough determination means that demodulates the two carrier compensation signals according to a signal arrangement having a reduced number of levels for multi-level modulation; a selection means that selects either the output from the symbol determination means or the output from the symbol rough determination means; and a coefficient setting means that refreshes a filter coefficient for a polarization-separation means, using the output selected by the selection means.