APD-based interference detectors yield 7-dB dynamic range of 70-krad/s PDM-DPSK endless polarization demultiplexer

Fast optical tracking and demultiplexing of DPSK/DQPSK/QAM polarization channels was hitherto limited to a fairly fixed optical input power. With APD photoreceivers used for residual interference detection, we demonstrate a 7…9-dB optical level tolerance.