Implications of Distributed Link Polarization-Dependent Loss on Bitwise Achievable Information Rates for Probabilistically Shaped and Uniform DP 64-QAM

The statistical behaviors of bitwise achievable information rates (BW AIRs) and effective signal-to-noise ratios (SNRs) due to polarization-dependent loss (PDL) are experimentally characterized for probabilistically shaped and uniform dual-polarization 64-ary quadrature amplitude modulation with a bit rate of 250 Gb/s. A single-span recirculating loop is used to emulate distributed link PDL. Histograms for the BW AIR and effective SNR following offline signal processing resemble shifted, mirror-image Maxwell probability density functions for both constellations and two different per-loop PDL values. For a transmission distance of 1200 km and a per-loop PDL of 1.3 dB, the outage probabilities for the shaped and uniform constellations are estimated to be $1.1\times 10^{-3}$ and $4.4\times 10^{-1}$ , respectively. Moreover, for an outage probability $\leq$ $4.0\times 10^{-3}$ , the increase in transmission distance due to shaping is reduced by 50% compared to that for PDL free transmission.