25.4-Tb/s Transmission Over Transpacific Distances Using Truncated Probabilistically Shaped PDM-64QAM

Probabilistic constellation shaping (PCS), digital nonlinear compensation, and multirate spatially coupled low-density parity check codes are used to achieve 25.4-Tb/s transmission over 10 285 km EDFA-only straight-line testbed at 6.1 bits/symbol/Hz. The gain provided by PCS over standard 64QAM is investigated over transatlantic and transpacific distances. Moreover, the potential benefits of nonlinear compensation based on digital-backpropagation versus algorithm complexity are addressed.