The intra- and inter- data center links face continuously increasing pressure on the transmission capacity while having to meet strict constraints in cost and power consumption. For such cost-sensitive data center applications, self-homodyne coherent (SHC) system as a promising solution has attracted increasing attention. In this article, the influence of phase noise (PN) for the SHC system is thoroughly analyzed by studying the PN probability distribution characteristic and bit-error rate (BER) performance in theory. The correctness of the theorical PN analysis is also verified by simulation. Further, the PN characteristics in SHC systems are investigated and discussed with and without the implementation of carrier phase recovery (CPR). A unique property is found for SHC systems that the system performance is only related to the product of linewidth and mismatch length, independent of the symbol rate in the absence of CPR. For SHC-16QAM systems, in order to limit the OSNR penalty to below 1-dB, the product of laser linewidth and delay mismatch should be kept below 0.18 ${\bf{MHz}} \cdot {\bf{m}}$ . Under such a conduciton, no CPR algorithm is reuiqred. Alternatively, in presence of CPR, the phase noise tolerance of SHC and conventional coherent systems are similar.

中文翻译：

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自同调相干系统中激光线宽和失配长度引起的相位噪声的理论分析

数据中心内和数据中心间的链路面临不断增加的传输容量压力，同时必须满足成本和功耗方面的严格限制。对于此类成本敏感的数据中心应用，自同调相干（SHC）系统作为一种有前途的解决方案受到了越来越多的关注。本文通过理论上研究PN概率分布特性和误码率（BER）性能，彻底分析了相位噪声（PN）对SHC系统的影响。仿真也验证了理论PN分析的正确性。此外，在有和没有实现载波相位恢复（CPR）的情况下，都将研究和讨论SHC系统中的PN特性。对于SHC系统，发现了一个独特的属性，即系统性能仅与线宽和失配长度的乘积相关，而与不存在CPR时的符号率无关。对于SHC-16QAM系统，为了将OSNR损失限制在1dB以下，激光线宽和延迟失配的乘积应保持在0.18以下$ {\ bf {MHz}} \ cdot {\ bf {m}} $ 。在这种情况下，不需要CPR算法。或者，在存在CPR的情况下，SHC和常规相干系统的相位噪声容限相似。