Optical networks, for 400G and beyond, require flexibility and agility from network elements, especially from coherent transceivers. Higher baud rates are made possible using new electrooptic technologies. Multi-dimensional modulation formats provide improved tolerance to noise and fiber nonlinearities. Constellation shaping further improves these tolerances while allowing a finer granularity in selection of capacity. Frequency division multiplexing also provides improved tolerance to the nonlinear characteristics of fiber. Algorithms with reduced computation complexity allow the implementation at-speed of direct precompensation of nonlinear propagation effects. FlexEthernet and FlexOTN allow network operators to optimize capacity on their optical transport networks.
"Flexible optical transceivers", Proc. SPIE 10561, Next-Generation Optical Communication: Components, Sub-Systems, and Systems VII, 1056104 (29 January 2018); doi: 10.1117/12.2295350; https://doi.org/10.1117/12.2295350