Flexible-Rate PON Based on Entropy-Loading DMT With Wide-Range Adjustment From 12.5 to 87.5 Gbps

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.