A Novel Nonlinear Equalizer for Probabilistic Shaping 64-QAM Based on Constellation Segmentation and Support Vector Machine

Abstract

The probability distribution of probabilistic shaping 64 quadrature amplitude modulation (PS-64QAM) is uneven. The traditional M-ary support vector machine (SVM) algorithm is incompatible with the data set with uneven distribution. In order to solve the problem, we propose a novel nonlinear equalizer (NLE) for PS-64QAM based on constellation segmentation (CS) and SVM, called CS M-ary SVM NLE. The performance of CS M-ary SVM NLE has been demonstrated in a 120 Gb/s PS-64QAM coherent optical communication system. The experimental results show that after employing the proposed scheme, the launched optical power dynamic range (LOPDR) of PS-64QAM can be increased by 1.6 dBm compared with the situation without NLE. In addition, aided by the proposed scheme, the LOPDR of PS-64QAM is increased by 0.6 dBm than M-ary SVM NLE. Compared with employing M-ary SVM NLE and without employing NLE, when employing the proposed scheme, the Q factor is improved about 0.50 dB and 0.96 dB, respectively. The number of support vectors (SVs) and CPU running time for both NLE schemes are collected to measure the complexity of the two NLE schemes. The results show that the complexity of the proposed scheme is lower than that of the M-ary SVM scheme under the entire measured launched optical power range from −5 dBm to +5 dBm.

Wavelength complement coding based a smooth hybrid MDM/C-NGPON evolution employing PS-512QAM modulation

“…10(b). It is the reason that expanding the shaping factor can decrease the Euclidean distance between neighbouring constellation points, ensuing in an insipid noise tolerance (Xu et al 2022). Besides this, Table 4 depicts the comparisons analysis in terms of NGMI limit of the system for varied fiber length in uplink and downlink direction operating at both mode 0 and 1.…”

“…Again, the probability distribution of PS-mQAM supports the Maxwell-Boltzmann (MB) distribution. The expression for PS-mQAM is given as (Xu et al 2022):…”

“…where 𝑦 𝑖 and v denote the ith constellation point in PS-mQAM and shaping parameter respectively. Also, as per the probability mass function,𝑃 𝑦 𝑖 , the entropy of PS-512QAM can be measured as (Xu et al 2022):…”

“…A polarization-division-multiplexed (PDM) using PS-1024QAM with 0.1-kHz linewidth has been experimentally demonstrated (Sasai et al 2020). In another work, (Xu et al 2022) a PS-64QAM over 375km distance at 120Gbps data rate has been proposed successfully. Also, a PS-256QAM over 75km at a 32Gbps data rate has been reported (Chen et al 2022).Thus, from these recent works, it is observed that no work has been done for C-NGPON employing PS-QAM modulation.…”