Abstract

We propose to introduce a controlled amount of inter-symbol interference (ISI) during pulse shaping in a high symbol rate intensity modulation direct detection (IM/DD) system to increase the alternating current (AC) power of the received electrical signal after photo-detection and transimpedance amplification. We experimentally demonstrate high-speed 4-level pulse amplitude modulation (PAM4) transmissions with a 4-λ coarse wavelength division multiplexing (CWDM) transmitter optical sub-assembly (TOSA) using the proposed scheme. The intentionally introduced ISI is mitigated using either transmitter-side Tomlinson Harashima precoding (THP) or receiver-side feed forward equalization (FFE) aided with a 2-tap post filter and maximum likelihood sequence estimation (MLSE). Both methods enable 4 × 81 Gbaud PAM4 transmission over 2 km of single mode fiber (SMF), with a bit error rate (BER) below the 7% overhead hard-decision forward error correction (HD-FEC) threshold of 3.8 × 10⁻³, which corresponds to a net rate of >600 Gb/s. We also explore the limit of our system at 10 km. The result shows that an aggregated net rate of 600 Gb/s excluding the HD-FEC overhead can still be achieved by loading different symbol rates onto different wavelength channels.

First demonstration of a 400 Gb/s 4λ CWDM TOSA for datacenter optical interconnects

Eslam El-Fiky, Mohamed Osman, Alireza Samani, Claude Gamache, Michael H. Ayliffe, Jingsi Li, Maxime Jacques, Yun Wang, Amar Kumar, and David V. Plant
Opt. Express 26(16) 19742-19749 (2018)

C-band 200 Gbit/s/λ PAM-4 transmission over 2-km SSMF using look-up-table pre-distortion combined with nonlinear Tomlinson-Harashima pre-coding

Yucheng Tu, Hailin Yang, Gai Zhou, Meng Xiang, Songnian Fu, Ming Tang, Yuwen Qin, and Luming Zhao
Opt. Express 30(9) 15416-15427 (2022)

Nonlinear Tomlinson-Harashima precoding for direct-detected double sideband PAM-4 transmission without dispersion compensation

Haiyun Xin, Kuo Zhang, Deming Kong, Qunbi Zhuge, Yan Fu, Shi Jia, Weisheng Hu, and Hao Hu
Opt. Express 27(14) 19156-19167 (2019)

Pairwise Tomlinson-Harashima precoding for multiple-lane IM-DD transmissions

Meng Xiang, Yongfeng Qiu, Can Wei, Gai Zhou, Jilong Li, Cong Zhang, Jianping Li, Songnian Fu, and Yuwen Qin
Opt. Express 32(6) 9245-9254 (2024)

Cost-minimizing distribution matching supporting net 800 Gbit/s PS-PAM transmission over 2 km using a 4-λ EML TOSA

Xueyang Li, Zhenping Xing, Md Samiul Alam, Maxime Jacques, Ping-Chiek Koh, and David V. Plant
Opt. Lett. 45(17) 4718-4721 (2020)