In this letter, an enhanced entropy loading discrete multi-tone (EEL-DMT) scheme is proposed for the flexible-rate passive optical network (PON). To achieve a wide range of rate adjustment with fine granularity and performance improvements, probabilistic constellation shaping (PCS)-quadrature amplitude modulation (QAM), quadrature phase shift keying (QPSK), and binary phase shift keying (BPSK) are combined in this scheme, and the modulation format of each subcarrier is determined by the allocated entropy. For verifying the feasibility of the proposed scheme, an O-band DMT system is experimentally demonstrated over 20-km standard single-mode fiber (SSMF) transmission using 10G-class directly modulated laser (DML). The experimental results show that the flexible-rate PON based on the EEL-DMT can achieve a wide-range rate adjustment from 12.5 Gb/s to 87.5 Gb/s under the optical power budget from 38 dB to 26 dB, and up to 2-dB receiver sensitivity gain is obtained compared with the adaptive bit and power loading (ABPL)-DMT.

中文翻译：

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基于熵加载 DMT 的灵活速率 PON，具有 12.5 至 87.5 Gbps 的宽范围调整

在这封信中，提出了一种用于灵活速率无源光网络（PON）的增强熵加载离散多音（EEL-DMT）方案。为了实现大范围的速率调整、细粒度和性能改进，该方案结合了概率星座整形（PCS）-正交幅度调制（QAM）、正交相移键控（QPSK）和二进制相移键控（BPSK） ，每个子载波的调制格式由分配的熵决定。为了验证所提出方案的可行性，使用10G级直接调制激光器（DML）对O波段DMT系统进行了20公里标准单模光纤（SSMF）传输的实验演示。实验结果表明，基于EEL-DMT的灵活速率PON可以在38 dB至26 dB的光功率预算下实现12.5 Gb/s至87.5 Gb/s的大范围速率调整，最高可达2与自适应比特和功率负载(ABPL)-DMT相比，获得了-dB接收器灵敏度增益。