The development of the fifth generation mobile (5G) technique stimulates a higher bandwidth requirement for next generation passive optical network (PON) systems. It is a challenge to further double the data rate from 50 to 100 Gb/s/λ depending on intensity modulation direct detection due to stringent bandwidth constraints on optical and electrical components. Coherent detection technology is a promising candidate for the future 100 Gb/s/λ or higher PON systems. The parallel implementation of hardware-efficient adaptive equalization tailored to PON systems will accelerate the evolution of coherent PON systems. In view of the current situation that logic resources are abundant while hardened multipliers are few for commercial field programmable gate array (FPGA), the purpose of this work is to reduce the number of hardened multiplexers used for FPGA realized signal processing. The waveform distortion caused by chromatic dispersion (CD) and imperfect frequency response of transceiver is rough compensated by using frequency domain equalization, which alleviate the stringent filter length requirement for the following adaptive equalization. Three Coordinate Rotation Digital Computer-based vector rotators are introduced to realize polarization demultiplexing, where the state of polarization is tracing by using a simplified gradient descent algorithm. A non-butterfly equalizer with few taps for each polarization is designed to handle the residual (CD) and the frequency response difference due to external environment variations and manufacturing technology. With the proposed method, the number of hardened multipliers is reduced by 73% compared with conventional 2×2 multiple-input multiple-output equalizer under the case with the similar receiver sensitivity.

中文翻译：

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相干 PON 系统硬件高效自适应均衡的并行实现

第五代移动 (5G) 技术的发展刺激了对下一代无源光网络 (PON) 系统的更高带宽需求。由于光和电子元件的严格带宽限制，根据强度调制直接检测将数据速率从 50 Gb/s/λ 进一步加倍是一项挑战。相干检测技术是未来 100 Gb/s/λ 或更高 PON 系统的有希望的候选者。针对 PON 系统的硬件高效自适应均衡的并行实现将加速相干 PON 系统的演进。针对目前商用现场可编程门阵列（FPGA）逻辑资源丰富而硬化乘法器少的现状，这项工作的目的是减少用于 FPGA 实现的信号处理的硬化多路复用器的数量。通过使用频域均衡粗略补偿由色散 (CD) 和收发器不完美频率响应引起的波形失真，从而减轻了后续自适应均衡对滤波器长度的严格要求。引入三坐标旋转数字计算机矢量旋转器来实现偏振解复用，其中偏振状态通过使用简化的梯度下降算法进行跟踪。每个极化具有很少抽头的非蝶形均衡器旨在处理由于外部环境变化和制造技术引起的残余 (CD) 和频率响应差异。使用所提出的方法，