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In the fiber transmission, a re-circulating loop is added between Tx and Rx in the experiment setup diagram to investigate performance under ASE noise and fiber nonlinearity. Inside a re-circulating loop, it is consisted of 80 km of a standard single-mode fiber (SMF), Erbium-doped fiber amplifier (EDFA) and optical band pass filter (OBPF). We adjust the number of re-circulating loops so independently in each entropy so that we can investigate the performance at BER around 0.01. As a result, all MAP-64 constellations in HPGS-64QAM outperform R-64 constellations in PS-64QAM for all cases. The shaping gains are 0.131, 0.050, and 0.020 for H(P) = 3.5, 4.0, and 5.0, respectively. The shaping gains are found to be increased as the signals are strongly shaped. |
IEEE/ICACT20210252 Slide.11
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