High sampling-rate digital-to-analog converters (DAC) are usually applied in optical fiber communication systems for the signal generation with advanced modulation formats such as four-level pulse amplitude modulation (PAM4). There exist various imperfections for high sampling-rate DACs. Clock tone leakage (CTL) is one of the imperfections and may seriously degrade the bit error rate (BER) performance, especially for single-carrier transmission systems. In this paper, we study a low-complexity time-domain averaging (TDA) based CTL compensation (TDA-CTLC) method for short-reach PAM4 transmission. By numerical simulation, we investigate the impacts of chromatic dispersion, CTL interference-to-signal power ratio (ISPR), and vertical resolution of the analog-to-digital converter on the BER performance. The results exhibit that the TDA-CTLC enabled PAM4 transmission system in the presence of a wide range of ISPR has a similar BER performance with the one without CTL interference. Moreover, we experimentally evaluate the compensation performance of the TDA-CTLC in a directly-modulated laser-based short-reach PAM4 transmission system. Up to −4 dB ISPR can be compensated with a slight BER performance degradation due to nonlinear distortions.

中文翻译：

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基于低复杂度时域平均的 DAC 时钟音泄漏补偿，用于短距离 PAM4 传输

高采样率数模转换器 (DAC) 通常应用于光纤通信系统中，以使用四级脉冲幅度调制 (PAM4) 等高级调制格式生成信号。高采样率 DAC 存在各种缺陷。时钟音泄漏 (CTL) 是缺陷之一，可能会严重降低误码率 (BER) 性能，尤其是对于单载波传输系统。在本文中，我们研究了一种用于短距离 PAM4 传输的基于低复杂度时域平均 (TDA) 的 CTL 补偿 (TDA-CTLC) 方法。通过数值模拟，我们研究了色散、CTL 干扰信号功率比 (ISPR) 和模数转换器的垂直分辨率对 BER 性能的影响。结果表明，TDA-CTLC 支持的 PAM4 传输系统在广泛的 ISPR 存在下具有与没有 CTL 干扰的系统相似的 BER 性能。此外，我们通过实验评估了 TDA-CTLC 在基于直接调制激光的短距离 PAM4 传输系统中的补偿性能。由于非线性失真，BER 性能略有下降，可以补偿高达 −4 dB 的 ISPR。