40-krad/s Polarization Tracking in 200-Gb/s PDM-RZ-DQPSK Transmission Over 430 km

We present real-time transmission of 50-Gbaud polarization-division-multiplexed (PDM) return-to-zero differential quadrature phase-shift keying (4 bit/symbol) over five fiber spans, 430 km in total. The two PDM channels are demultiplexed using a beam splitter and automatic optical polarization control with interference detection. For the first time, PDM signal tracking speeds of up to 40 krad/s are demonstrated.