Trans-Atlantic field trial using probabilistically shaped 64-QAM at high spectral efficiencies and single-carrier real-time 250-Gb/s 16-QAM

We transmitted probabilistically shaped 64-QAM at 7.46 b/s/Hz over a 5,523-km inservice EDFA-only amplified trans-Atlantic cable (5.68 b/s/Hz over a looped-back 11,046 km). Using real-time processing we achieve single-carrier 250-Gb/s 16-QAM at 4 b/s/Hz.