Bit-Wise Achievable Information Rates for Probabilistically Shaped 64-QAM in the Presence of Bandwidth Narrowing due to Cascaded Wavelength Selective Switches

An efficient procedure is presented for evaluating the performance implications of bandwidth narrowing due to cascaded WSSs on probabilistically shaped and uniform 64- QAM using the BW AIR. The constellation distribution that yields the optimum shaping gain in BW AIR for a given SNR depends on the extent of the narrowing.