SIGNAL PROCESSING APPARATUS AND SIGNAL PROCESSING METHOD
One aspect of the present invention provides a signal processing apparatus including: filter processors, the number of the filter processors depending on the number of spatial modes of a received optical signal; a sum operator that outputs a sum of outputs of a plurality of the filter processors; an IFFT processor that performs inverse Fourier transform on the sum; an output signal selector that outputs a signal including only a predetermined part of an output of the IFFT processor; an error signal output that outputs, as an error signal, a difference between an output of the output signal selector and a desired signal; and an FFT processor that performs Fourier transform on signals including the error signal, in which the filter processors update a filter weight coefficient by using a signal obtained by performing multiplication only on a predetermined part for an output of the FFT processor and a signal obtained by performing processing including Fourier transform on the received optical signal, and the filter processors output a signal obtained by performing multiplication only on a predetermined part for the filter weight coefficient and the received optical signal.
1 . A signal processing apparatus comprising:
filter processors, the number of the filter processors depending on the number of spatial modes of a received optical signal;
a sum operator that outputs a sum of outputs of a plurality of the filter processors;
an IFFT processor that performs inverse Fourier transform on the sum;
an output signal selector that outputs a signal including only a predetermined part of an output of the IFFT processor;
an error signal output that outputs, as an error signal, a difference between an output of the output signal selector and a desired signal; and
an FFT processor that performs Fourier transform on signals including the error signal,
wherein the filter processors update a filter weight coefficient by using a signal obtained by performing multiplication only on a predetermined part for an output of the FFT processor and a signal obtained by performing processing including Fourier transform on the received optical signal, and
the filter processors output a signal obtained by performing multiplication only on a predetermined part for the filter weight coefficient and the received optical signal.
2 . The signal processing apparatus according to claim 1 , wherein the filter processors perform multiplication on a portion corresponding to a component of a signal band in a frequency domain as the predetermined part.
3 . The signal processing apparatus according to claim 1 , wherein the output signal selector outputs a signal including components of every (m−1) index numbers in a case where an oversampling rate of the received optical signal is m.
4 . A signal processing method performed by a signal processing apparatus including filter processors, the number of the filter processors depending on the number of spatial modes of a received optical signal, the signal processing method comprising:
outputting a sum of outputs of a plurality of the filter processors;
performing inverse Fourier transform on the sum;
outputting an output signal including only a predetermined part of an output of the inverse Fourier transform;
outputting, as an error signal, a difference between the output signal and a desired signal; and
performing Fourier transform on signals including the error signal,
wherein the filter processors update a filter weight coefficient by using a signal obtained by performing multiplication only on a predetermined part for a result obtained by performing Fourier transform on the signals including the error signal and a signal obtained by performing processing including Fourier transform on the received optical signal, and
the filter processors output a signal obtained by performing multiplication only on a predetermined part for the filter weight coefficient and the received optical signal.
5 . The signal processing apparatus according to claim 2 , wherein the output signal selector outputs a signal including components of every (m−1) index numbers in a case where an oversampling rate of the received optical signal is m.