Endless Optical Polarization Control at 56 krad/s, Over 50 Gigaradian, and Demultiplex of 112-Gb/s PDM-RZ-DQPSK Signals at 3.5 krad/s

In this paper, we present an field-programmable gate array-based automatic endless optical polarization control system, which drives a commercial LiNbO
₃
polarization transformer. It is capable of tracking endless polarization changes of up to 56 krad/s with mean and maximum polarization errors of 0.077 and 0.197 rad, respectively. While tracking up to 50 krad/s, the system was likewise tested over >2 weeks with maximum polarization error of 0.195 rad during which time it tracked polarization changes of 50 Gigaradian. 112-Gb/s polarization-division multiplexed return to zero differential quadrature phase-shift keying transmission with direct detection and polarization scrambling up to 3.5 krad/s is also demonstrated.