Shu Liang, Yu Zhenming, Wan Zhiquan, Xu Kun
Opt Express. 2020 Jun 8;28(12):17841-17852. doi: 10.1364/OE.394412.
In this paper, the application of a clipping and digital resolution enhancer (DRE) is numerically investigated in 56-GBaud direct-detection four-ary pulse amplitude modulation (PAM4) transmission systems. The influence of the tap length and the digital-to-analog converter (DAC) samples per symbol on DRE gain is first studied. After optimizing clipping probability, sampling jitter is introduced. The combination of clipping and DRE can increase jitter tolerance by ∼1.7% sampling time for 4-bit DAC. Then, the required optical signal-to-noise ratio (OSNR) at the hard-decision forward error correction (HD-FEC) threshold of 3.8×10 is investigated in back-to-back case and 80-km fiber transmission. It is shown that the combination of clipping and DRE can reduce the required OSNR significantly for 3-bit and 4-bit DAC. Finally, the performance gain introduced by clipping and DRE is analyzed from a perspective of the transmitted average signal power and the received mean-squared quantization error.
在本文中，对削波和数字分辨率增强器（DRE）在56GBaud直接检测四电平脉冲幅度调制（PAM4）传输系统中的应用进行了数值研究。首先研究了抽头长度和每个符号的数模转换器（DAC）采样对DRE增益的影响。在优化削波概率后，引入了采样抖动。对于4位DAC，削波和DRE的组合可将抖动容限提高约1.7%采样时间。然后，在背对背情况和80公里光纤传输中，研究了硬判决前向纠错（HD-FEC）阈值为3.8×10时所需的光信噪比（OSNR）。结果表明，对于3位和4位DAC，削波和DRE的组合可显著降低所需的OSNR。最后，从发射平均信号功率和接收均方量化误差的角度分析了削波和DRE引入的性能增益。
