通信工程文献翻译——传统的Gardner时钟恢复方法对具有sinc脉冲形状的奈奎斯特信号失效。 提出一种新的算法，并通过实验验证。 它具有较低的定时抖动，并且研究其对各种失真的容限。在现代相干系统中，定时信息的质量主要由未补偿的色散（CD）和偏振模色散（PMD）的量支配。 与其中在时钟提取之前不能数字补偿大残余色散的直接检测系统相反，商业相干接收机在完全或部分CD和PMD补偿之后提取时钟。 补偿块引入了对时序至关重要的延迟，并且时钟恢复需要非常具体的架构。 在检查适用于光学系统的相位检测器（PD）之后，我们选择最佳候选者并且为两种最流行的传输场景提出实施结构。

1. 介绍

奈奎斯特脉冲成形是实现高光谱效率相干光通信的有吸引力的手段。 为了实现最小信号带宽而不引入符号间干扰，发射脉冲应具有sinc形状。 在接收机处，需要时钟恢复来维持数字信号处理（DSP）和接收信号的时钟之间的同步。 Gardner方法由于其载波相位的简单性和独立性而被广泛使用[1-5]，然而，其性能在具有小滚降因子的奈奎斯特信号上降级[6-8]。 在本文中，我们提出一种新颖的奈奎斯特信号的时钟恢复算法，并通过实验验证。 研究了所提出的方法的定时抖动及其对各种失真（诸如激光频率偏移，色散（CD），差分群延迟（DGD）和偏振相关损耗（PDL））的耐受性。

1.1.加德纳法和提出的方法

作为定时误差检测器（TED），熟知的Gardner方法[1]使用以下......

其中I和Q表示接收信号的同相和正交相位分量。 采样率假定为2个采样/符号，下标表示采样索引。 TED，EG的输出是指示采样阶段是早还是晚的定时误差。 求和（平均）长度M提供了跟踪速度和噪声抑制之间的折衷。 方程（1）可以重写......

Abstract：Conventional Gardner clock recovery method fails on Nyquist signal with sinc pulse shape. A novel algorithm is proposed and verified by experiment. It has lower timing jitter, and its tolerance to various distortions is investigated.In modern coherent systems, the quality of timing information is mainly dominated by the amount of uncompensated chromatic dispersion (CD) and polarization mode dispersion (PMD). Contrary to direct-detection systems in which large residual dispersion cannot be digitally compensated before clock extraction, commercial coherent receivers extract a clock after full or partial CD and PMD compensation. Compensation blocks introduce a delay that is critical for timing, and clock recovery requires a very specific architecture. After reviewing phase detectors (PDs) applicable to optical systems, we select the best candidates and propose implementation structures for two most popular transmission scenarios.

1. Introduction

The Nyquist pulse shaping is an attractive means to enable high spectral efficiency coherent optical communication. To achieve minimal signal bandwidth without introducing inter-symbol interference, the transmitted pulse should have sinc shape. At the receiver, clock recovery is required to maintain synchronization between the digital signal processing (DSP) and the clock of the received signal. The Gardner method is widely used due to its simplicity and independence of carrier phase [1-5], however, its performance degrades on Nyquist signal with small ......