Record 59-krad/s Polarization Tracking in 112-Gb/s 640-km PDM-RZ-DQPSK Transmission

We present results obtained with a fast optical polarization controller. Tracking errors were <; 0.208 rad on the Poincaré sphere during 282 hours of endless polarization scrambling at up to 60 krad/s speed. Fifty-kilorad/second polarization changes were tracked at wavelengths between 1513 nm and 1600 nm. With this subsystem we optically demultiplexed the two polarizations of a 112-Gb/s PDM-RZ-DQPSK signal transmitted over 640 km of fiber at 59 krad/s. This is the fastest polarization control reported for this or higher bitrate and direct detection.