Patent ID: 8437632

Claim:
An optical communications receiver comprising: an optical input port to receive a polarization division multiplexed (PDM) signal comprising two orthogonally polarized optical signals, such that one of the two optical signals is RF-modulated, the PDM signal being received to the optical communications receiver through an optical line; a polarization beam splitter to de-multiplex the received PDM signal; and a monitoring unit to monitor a polarization state of the received PDM signal, the monitoring unit being arranged and configured to: extract, prior to demultiplexing the PDM signal, a monitoring signal from the received PDM signal, such that a polarization state of the monitoring signal is substantially the same as the polarization state of the received PDM signal, measure the polarization state of the monitoring signal, and compare the measured polarization state with a target polarization state determined during a previously performed calibration procedure.