Optical Phase Estimators in Modern Homodyne Communications Systems

Abstract

This work consists of the synthesis of an optimal  estimator for a random  phase modulation onto a carrier to be received by a coherent detector Our application is oriented to homodyne detection with PSK format, in modern optical communication systems. We mechanize an estimator operating with a baseband obsevable in additive noise  employing  a state variable  model for the communication  channel and optimal estimation techniques. To assess the performance  of the general structure  and simplified versions of the estimator we made computer simulations and calculated  the r.m.s value of the phase error. With these results we get practical estimators that we implemented using analog electronic circuitry and a DSP. The "constant variance" estimator exhibited the minimum r.m.s value of its phase error obtained experimentally.