为了应对不断增长的超千兆需求，从千兆走向万兆，从第五代固定网络（F5G）走向高级第五代固定网络（F5.5G），50 Gbit/s无源光网络（PON）被认为是F5.5G的重要组成部分。故文章针对当前接入网络发展状况，对50 Gbit/s PON技术进行了深入研究。

文章首先介绍了实现50 Gbit/s PON高灵敏度面临的困难，并提出了解决方案。方案中，50 Gbit/s的非归零（NRZ）信号通过雪崩光电二极管（Avalanche Photodiode，APD）探测器，在强电场的作用下形成可被检测到的宏观电流，该电流通过跨阻放大器（TIA）放大并转换成电压输出。对其进行均衡处理，采用光数字信号处理（oDSP）芯片的前馈均衡器（FFE）和判决反馈均衡器（DFE）对脉冲信号的拖尾现象进行补偿后，再通过DFE将码间干扰的影响降到最低。接着重点分析了APD、TIA和oDSP等关键技术，并采用25与50 Gbit/s APD对接收性能进行比较。

两组实验测试结果显示，第1组实验25 Gbit/s APD在测试时间4 min内接收信号无误码，接收光功率为－8.48 dBm，当误码率（BER）为2.78e^－2时，接收光功率达－26.61 dBm；在使用50 Gbit/s APD的情况下，4 min内接收信号无误码时，接收光功率为－8.97 dBm。当BER为2.78e^－2时，接收光功率达到－27.05 dBm，第2组数据50 Gbit/s APD-2也达到了同样的实验效果。

50 Gbit/s APD接收灵敏度更高，性能更好，更适合使用在50 Gbit/s PON光模块中实现高性能接收。最后文章针对未来降成本方案在均衡技术与APD上的应用提出了可行性分析。

In order to meet the growing demand for ultra-gigabit, from gigabit to 10-gigabit, from The 5th Generation Fixed networks (F5G) to F5G-Advanced (F5.5G), 50 Gbit/s Passive Optical Network (PON) is considered to be an important part of F5.5G. This paper conducts a thorough study of 50 Gbit/s PON technology, reflecting the latest advancements in access networks.

This paper initially addresses the difficulties in achieving high sensitivity in 50 Gbit/s PON, and proposes a solution. 50 Gbit/s Non-Return-to-Zero (NRZ) signals pass through Avalanche Photodiode (APD) detectors to form macroscopic currents that can be detected under strong electric fields. These currents are then amplified by a Transresistance Amplifier (TIA) and converted into voltage outputs. After balancing, the Feed Forward Equalizer (FFE) and Decision Feedback Equalizer (DFE) of optical Digital Signal Processing (oDSP) chip are used to compensate the trailing phenomenon of pulse signal, and the influence of intersymbol interference is minimized by DFE. Then the paper analyses the key technologies such as APD, TIA and oDSP, comparing the reception performance between 25 Gbit/s and 50 Gbit/s APDs.

Experimental test results show that the 25 Gbit/s APD maintains error-free signal reception at -8.48 dBm over 4 minutes, and reaches -26.61 dBm at a Bit Error Rate(BER) of 2.78e-2. The 50 Gbit/s APD exhibits no bit errors at -8.97 dBm and achieves -27.05 dBm at the same BER, with the second 50 Gbit/s APD set demonstrating similar results.

The 50 Gbit/s APD has superior receiving sensitivity and performance, making it highly suitable for 50 Gbit/s PON optical modules to help achieve high receiver sensitivity. The paper suggests a feasible approach for cost reduction in future implementations, focusing on the balance technology and APD.