Balancing the benefits inherent in reconfigurable coherent optical transceivers

Starting with transmission performance from commercially available 100+ Gb/s DP-QPSK transceivers, we calculate relative distance reach penalties and corresponding spectral efficiency improvements made possible with DSP-based pulse shaping and quasi-Nyquist subcarrier spacing. Modulation formats for nominal rate 400 Gb/s and 1.6 Tb/s superchannels, for different symbol rates, subcarrier spacing, and guardbands are considered in the context of a flexible grid. A 12.5 GHz frequency slot granularity results in discretization of operating parameters. Cases are highlighted in which distance reach penalties are incurred without the desired improvements in spectral efficiency; avoidance of such cases is expected to increase link reliability.