Signal processing apparatus and signal processing method

摘要

Signal processing means includes carrier compensation means for compensating for a phase difference and a frequency difference between signal light and local light in relation to two polarization signals, so as to generate two carrier compensated signals, symbol determination means for demodulating the two carrier compensated signals on the basis of a signal arrangement of multi-value modulation, symbol rough-determination means for demodulating the two carrier compensated signals on the basis of a signal arrangement in which the number of multi-values of the multi-value modulation is reduced, selection means for selecting either of an output of the symbol determination means and an output of the symbol rough-determination means, and coefficient setting means for updating filter coefficients of polarized wave separation means by using an output selected by the selection means.

主权项

1. A signal processing apparatus comprising:
polarized wave separation unit for receiving four digital signals and generating two polarization signals corresponding to two polarization components of signal light from the four digital signals by using filters having filter coefficients, the four digital signals being generated by performing photoelectric conversion and analog-digital conversion on four output light beams which are generated by making the signal light having undergone polarization division multiplexing and multi-value modulation and local light interfere with each other by using a 90° optical hybrid; carrier compensation unit for compensating for a phase difference and a frequency difference between the signal light and the local light in relation to the two polarization signals, so as to generate two carrier compensated signals; determination unit for demodulating the two carrier compensated signals; selection unit for selecting whether the determination unit performs the demodulation based on a signal arrangement of the multi-value modulation or based on a signal arrangement in which a number of multi-values of the multi-value modulation is reduced; and coefficient setting unit for updating the filter coefficients of the polarized wave separation unit by using an output selected by the selection unit.