Digital signal processing apparatus

摘要

A parameter of an adaptive filter is optimized so that inter-symbol interference having an amount corresponding to an inserted fixed filter remains. A digital signal processing apparatus which is included in an optical signal receiver and processes a digital signal converted from an optical signal is provided with: a linear adaptive filter which applies a dynamically controllable linear transfer function to the digital signal; a maximum likelihood sequence decoder which applies a transfer function of a transmission-path model to a plurality of signal sequence candidates to generate a plurality of reference signals, and decodes a reception signal using maximum likelihood sequence estimation which evaluates the differences between an output signal of the linear adaptive filter and the reference signals to estimate the most likely transmission time sequence; a signal regenerator which generates a signal corresponding to decoded data from the maximum likelihood sequence decoder; a feedback distortion adding filter which adds distortion that is equivalent to the transmission-path model used in the maximum likelihood sequence decoder to an output signal of the signal regenerator; and an adaptive equalization filter control block which updates a tap coefficient of the linear adaptive filter in accordance with an LMS algorithm using the difference between a target signal that is an output signal of the feedback distortion adding filter and the digital signal as an error signal.

主权项

1. A digital signal processing apparatus which is included in an optical signal receiver for use in optical fiber communication and processes a digital signal converted from an optical signal by a photoelectric conversion apparatus and an analog/digital converter, the digital signal processing apparatus comprising:
a linear adaptive filter which inputs the digital signal, applies a dynamically controllable linear transfer function to the input digital signal, and outputs a resultant signal; a maximum likelihood sequence decoder which inputs an output signal of the linear adaptive filter, applies a transfer function of a transmission-path model to a plurality of signal sequence candidates to generate a plurality of reference signals, and decodes a reception signal using maximum likelihood sequence estimation which evaluates the differences between the output signal of the linear adaptive filter that has been input and the reference signals to estimate the most likely transmission time sequence; a signal regenerator which inputs decoded data from the maximum likelihood sequence decoder and generates a signal corresponding to the decoded data; a feedback distortion adding filter which input an output signal from the signal regenerator, applies distortion equivalent to the transmission-path model used in the maximum likelihood sequence decoder to the output signal of the signal regenerator, and outputs a resultant signal; and an adaptive equalization filter control block which inputs an output signal of the feedback distortion adding filter as a target signal, inputs the digital signal input to the linear adaptive filter, and updates a tap coefficient of the linear adaptive filter in accordance with a least mean square (LMS) algorithm using the difference between the target signal and the input digital signal as an error signal.