Performance Dependence on Channel Baud-Rate of PM-QPSK Systems Over Uncompensated Links

We investigated through simulation the performance of dense wavelength-division-multiplexing transmission systems based on polarization-multiplexed quadrature phase-shift keying over long-haul uncompensated links. We looked at three system configurations, whose per-channel Baud-rate was 14, 28, and 56 GBaud, respectively. Their total net capacity in the C-band (8 Tb/s) and net spectral efficiency (2 b/s/Hz) were exactly the same. We found that the systems long-haul performance is almost the same in the three cases, with the 56-GBaud configuration only slightly under-performing. By means of backward-propagation, we also found that the balance between intrachannel and interchannel nonlinear (NL) effects is completely different in the three cases, with 14-GBaud dominated by interchannel NL effects and 56-GBaud dominated by single-channel NL effects. We also show that, where possible to actually exploit backward-propagation, the 56-GBaud per channel system would outperform the lower Baud-rate configurations.