224-Gb/s POLMUX-RZ-16QAM for next generation high-capacity optical transmission systems

In this paper, we study the 224-Gb/s polarization multiplexed, return to zero, 16-level quadrature amplitude modulation (POLMUX-RZ-16QAM) as a candidate for next generation high capacity optical transmission systems. We discuss the main challenges associated with the generation of such multi-level optical modulation format. Furthermore, we demonstrate the generation and transmission of eleven 224-Gb/s POLMUX-RZ-16QAM channels over a transmission distance of up to 1500 km with a spectral efficiency of 4 b/s/Hz. Finally, we give our outlook on how future optical systems will evolve to realize data rates beyond 200 Gb/s per channel.