Signal processing in an optical polarization diversity receiver for560-Mbit/s ASK heterodyne detection

Polarization diversity is an alternative technique for coherent receivers to prevent loss to signal due to variations in the states of polarization (SOP) of the received signal field. It is shown experimentally and theoretically that there is no significant power penalty difference between a receiver with optimally adjusted gains and receivers with linear envelope detection and square-law detection. Experimentally, two amplitude-shift keying (ASK) heterodyne polarization diversity receivers with envelope detectors were demonstrated at 560 Mb/s, one using linear rectifiers, the other using square-law rectifiers. In both cases, the receiver sensitivity of -35 dBm at BER=10 ^-9 was degraded by less than 1 dB as the received signal SOP was varied, in agreement with theory