SIGNAL PROCESSING APPARATUS, SIGNAL PROCESSING METHOD, AND COMPUTER PROGRAM
Provided is a signal processing device including: a batch adaptive equalization unit configured to use a first adaptive filter to perform an equalization process of waveform distortion on each polarized digital signal obtained by performing analog-to-digital conversion on a polarization-multiplexed signal; a matrix conversion unit configured to acquire filter coefficients of the first adaptive filter from at least the batch adaptive equalization unit, and convert acquired the filter coefficients through matrix operation; a degree-of-freedom separation adaptive equalization unit configured to use a second adaptive filter including the filter coefficients converted by the matrix conversion unit to perform an equalization process of waveform distortion due to polarization state fluctuation in a transmission path on each polarized digital signal; and a switching control unit configured to select a signal equalized by the batch adaptive equalization unit or the degree-of-freedom separation adaptive equalization unit as a reception signal.
1 . A signal processing device comprising:
a batch adaptive equalizer configured to use a first adaptive filter to perform an equalization process of waveform distortion on each polarized digital signal obtained by performing analog-to-digital conversion on a polarization-multiplexed signal;
a matrix converter configured to acquire filter coefficients of the first adaptive filter from at least the batch adaptive equalizer, and convert acquired the filter coefficients through matrix operation;
a degree-of-freedom separation adaptive equalizer configured to use a second adaptive filter including the filter coefficients converted by the matrix converter to perform an equalization process of waveform distortion due to polarization state fluctuation in a transmission path on each polarized digital signal; and
a switching controller configured to select a signal equalized by the batch adaptive equalizer or the degree-of-freedom separation adaptive equalizer as a reception signal.
2 . The signal processing device according to claim 1 , wherein the degree-of-freedom separation adaptive equalizer performs an equalization process using, as the second adaptive filter, a filter of which filter coefficients are represented as a product of a matrix indicating a degree of freedom of polarization state fluctuation and a matrix indicating a degree of freedom obtained by subtracting the polarization state fluctuation from a degree of freedom of transceiver characteristics.
3 . The signal processing device according to claim 1 , wherein the degree-of-freedom separation adaptive equalizer updates the filter coefficients of the second adaptive filter with a low frequency resolution when updating coefficients corresponding to the degree of freedom of the polarization state fluctuation.
4 . The signal processing device according to claim 1 , wherein the switching controller selects any of the signals equalized by the batch adaptive equalizer or the degree-of-freedom separation adaptive equalizer as the reception signal on the basis of an elapsed time, a quality of an equalized signal, or a signal from outside.
5 . A signal processing method comprising:
using a first adaptive filter to perform an equalization process of waveform distortion on each polarized digital signal obtained by performing analog-to-digital conversion on a polarization-multiplexed signal;
acquiring filter coefficients of at least the first adaptive filter, and converting acquired the filter coefficients through matrix operation;
using a second adaptive filter including the converted filter coefficients to perform an equalization process of waveform distortion due to polarization state fluctuation in a transmission path on each polarized digital signal; and
selecting a signal that has undergone the equalization process using the first adaptive filter or the equalization process using the second adaptive filter as a reception signal.
6 . A non-transitory storage medium that stores a program for making a computer perform processes, the processes comprising:
using a first adaptive filter to perform an equalization process of waveform distortion on each polarized digital signal obtained by performing analog-to-digital conversion on a polarization-multiplexed signal;
acquiring filter coefficients of at least the first adaptive filter and converting acquired the filter coefficients through matrix operation;
using a second adaptive filter including the converted filter coefficients to perform an equalization process of waveform distortion due to polarization state fluctuation in a transmission path on each polarized digital signal; and
selecting a signal that has undergone the equalization process using the first adaptive filter or the equalization process using the second adaptive filter as a reception signal.