HARDWARE EFFICIENT IMPLEMENTATION OF DECISION FEEDBACK PHASE ESTIMATION FOR AN ULTRA HIGH SPEED COHERENT RECEIVER

摘要

A method for estimating the phase of a modulated complex optical signal, according to which, the phase of the signal is isolated and the complex amplitude of the signal is digitized by a block of P samples. An adaptive filter minimizes phase-error between the phase of the received symbol and the phase of a sample, rotated by a phase correction factor, by iteratively performing a Block-Wise Phase LMS estimation on the samples using a step size parameter. During each iteration, the resulting correction factor consists of the sum of the estimated errors multiplied by this parameter, and the correction factor of previous iteration, which is updated, until obtaining the final correction factor from the last iteration. The samples constituting the received signal are recovered by adding the most updated correction factor to the phase of each sample and performing a decision regarding the phase of each sample.

主权项

1. A method for estimating the phase of a modulated complex carrier signal transmitted by a laser source to a coherent receiver, via an optical channel, comprising:
a) isolating the phase of said signal, in the phase plane of the complex signal; b) determining a block of P samples for digitizing the complex amplitude of said signal, according to the rate of phase variations of said channel and the amount of noise in said channel; c) determining a digitized phase-error being the difference between the phase of the digitized decoded symbol received by said receiver and the phase of a sample being the digitized complex amplitude detected by said coherent receiver, rotated by a phase correction factor on the complex plane; d) constructing an adaptive filter to minimize said phase-error, by:
d.1) iteratively performing a Block-Wise Phase LMS estimation on said P samples according to a step size parameter, determined by a desired convergence rate, while during each iteration, the resulting correction factor consists of the sum of the estimated errors of the P samples in the current iteration multiplied by said step size parameter, and the correction factor of previous iteration;d.2) updating the correction factor during each iteration until obtaining the final correction factor from the last iteration; andd.3) recovering the samples constituting the received signal by adding the most updated correction factor to the phase of each sample removing 2π cycles from the resulting phase and performing a decision regarding the phase of each sample.