Field Trial of a 1 Tb/s Super-Channel Network Using Probabilistically Shaped Constellations

We successfully tested the suitability of probabilistically shaped constellations in a German nationwide fiber ring of the R&D field test network of Deutsche Telekom. In this ring, eight German cities can be reached by add/drop nodes implemented by passive optical add/drop multiplexers, offering 12 bands of 400 GHz widths in the extended C-band. Multiple cascaded add/drop multiplexers are reducing the available bandwidth. We transmitted a 1 Tb/s four-carrier super-channel with an extended family of probabilistically shaped constellations using 16QAM, 36QAM, and 64QAM and variable bandwidth. We verified in the field environment by two examples that probabilistic shaping is outperforming standard 64QAM and 16QAM formats in reach. We experimentally tested two typical 1 Tb/s working paths with 419 and 951 km, demonstrating spectral efficiencies of 6.75 and 5 bit/s/Hz, respectively. The maximum reach of about 1500 km was extrapolated for a 1 Tb/s probabilistically shaped super-channel transmitted in a 200 GHz bandwidth. For protection paths with longer distances than 1500 km, the spectral efficiency has to be reduced with the net-bitrate in steps of 100 Gb/s. For the longest bidirectional path of the test network, i.e., a protection path of 2159 km, the maximum achieved net-bitrate was 800 Gb/s.