Trellis-Coded Modulation-Enabled Probabilistic Shaping With Simplified Viterbi Decoder for Bandwidth-Limited IMDD Systems

• Published in: IEEE Photonics Journal
• Main Authors: Han Cui, Zhongliang Sun, Xiaoqian Huang, Du Tang, Fei Xie, Yaojun Qiao
• Format: Article in Journal/Newspaper
• Language: English
• Published: IEEE 2023
• Subjects: Probabilistic shaping; trellis-coded modulation; bandwidth-limited; IMDD system; Viterbi decoder; Applied optics. Photonics; TA1501-1820; Optics. Light; QC350-467; DML
• Online Access: https://doi.org/10.1109/JPHOT.2023.3314028; https://doaj.org/article/d933fd0789e242969b83031855765d26

In this article, trellis-coded modulation-enabled probabilistic shaping (TEPS) scheme with a simplified Viterbi decoder is proposed. Trellis-coded modulation (TCM) is embedded in the probabilistic shaping (PS) technique to improve the performance of PS signals in bandwidth-limited intensity modulation and direct detection (IMDD) systems. Further, to reduce the calculation complexity of TCM decoding, the constellation partition decision-assisted (CPDA)-Viterbi decoder is proposed which decides the received signal before decoding to reduce the branches. To verify the performance of the proposed scheme, a 32-GBaud TEPS-four-level pulse-amplitude modulation (PAM4) experimental system with 10G-class O-band directly-modulated laser (DML) is built over a 20-km standard single-mode fiber (SSMF) transmission link. The experimental results show that TEPS-PAM4 achieved up to 1.80-dB higher receiver sensitivity than PS-PAM4 at 7% forward error correction (FEC) limit with the same net rate. Moreover, with the multiplications reduced by up to 45.7% compared with the Viterbi decoder, TEPS-PAM4 with CPDA-Viterbi decoder has up to 1.50-dB higher receiver sensitivity limit than PS-PAM4 at 7% FEC.