Beyond 200-Gb/s O-band intensity modulation and direct detection optics with joint look-up-table-based predistortion and digital resolution enhancement for low-cost data center interconnects
Qi Wu, Zhaopeng Xu, Yixiao Zhu, Tonghui Ji, Honglin Ji, Yang Yu, Junpeng Liang, Chen Cheng, Gang Qiao, Zhixue He, Jinlong Wei, Qunbi Zhuge, Weisheng Hu
Abstract
We propose a joint look-up-table (LUT)-based nonlinear predistortion and digital resolution enhancement scheme to achieve high-speed and low-cost optical interconnects using low-resolution digital-to-analog converters (DACs). The LUT-based predistortion is employed to mitigate the pattern-dependent effect (PDE) of a semiconductor optical amplifier (SOA), while the digital resolution enhancer (DRE) is utilized to shape the quantization noise, lowering the requirement for the resolution of DAC. We experimentally demonstrate O-band intensity modulation and direct detection (IM/DD) transmission of 124-GBd 4/6-level pulse-amplitude modulation (PAM)-4/6 and 112-GBd PAM-8 signals over a 2-km standard single-mode fiber (SSMF) with 3/3.5/4-bit DACs. In the case of 40-km SSMF transmission with an SOA-based preamplifier, 124-GBd on-off-keying (OOK)/PAM-3/PAM-4 signals are successfully transmitted with 1.5/2/3-bit DACs. To the best of our knowledge, we have achieved the highest net data rates of 235.3-Gb/s PAM-4, 289.7-Gb/s PAM-6, and 294.7 Gb/s PAM-8 signals over 2-km SSMF, as well as 117.6-Gb/s OOK, 173.8-Gb/s PAM-3, and −231.8 Gb/s PAM-4 signals over 40-km SSMF, employing low-resolution DACs. The experimental results reveal that the joint LUT-based predistortion and DRE effectively mitigate the PDE and improve the signal-to-quantization noise ratio by shaping the noise. The proposed scheme can provide a powerful solution for low-cost IM/DD optical interconnects beyond 200 Gb/s.