The amount of data center traffic is rapidly increasing, and it is necessary for short-reach optical transmission such as Ethernet to realize a higher capacity data link. Therefore, the next-generation Ethernet links will require the higher data rate. In such a situation, transmission distance is limited by the bandwidth limitation due to optical and electrical devices in the Ethernet transceiver. In this article, we propose a nonlinear-coded-modulation which shapes the signal spectrum in order to realize the higher tolerance to bandwidth limitation. We apply this technique to a 92-Gbaud PAM4 signal and confirm that the proposed technique achieves the 7% HD-FEC threshold in 184-Gb/s transmission with the bandwidth limitation of 20 GHz through an O-band 10-km transmission experiment. We also investigate the applicability of MLSE to the proposed technique and show that the KP4-FEC threshold can be achievable with 2-memory MLSE and 5-tap channel-shortening filter. In addition, we study the applicability of the proposed technique to a QAM signal which is conventionally utilized in coherent systems. We compare the proposed nonlinear-coded QAM to the conventional duobinary QAM and show that the performance of the proposed QAM signal is greater than that of the duobinary QAM signal with MLSE where the signal degradation is induced by additive white Gaussian noise.

中文翻译：

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基于非线性编码调制的短距离光传输频谱整形技术

数据中心流量快速增长，以太网等短距离光传输需要实现更高容量的数据链路。因此，下一代以太网链路将需要更高的数据速率。在这种情况下，由于以太网收发器中的光电器件，传输距离受到带宽限制。在本文中，我们提出了一种对信号频谱进行整形的非线性编码调制，以实现对带宽限制的更高容忍度。我们将此技术应用于 92 Gbaud PAM4 信号，并通过 O 波段 10 公里传输实验确认所提出的技术在 184 Gb/s 传输中达到 7% HD-FEC 阈值，带宽限制为 20 GHz。我们还研究了 MLSE 对所提出技术的适用性，并表明使用 2 内存 MLSE 和 5 抽头通道缩短滤波器可以实现 KP4-FEC 阈值。此外，我们研究了所提出的技术对通常用于相干系统的 QAM 信号的适用性。我们将所提出的非线性编码 QAM 与传统的双二进制 QAM 进行比较，并表明所提出的 QAM 信号的性能优于具有 MLSE 的双二进制 QAM 信号，其中信号劣化是由加性高斯白噪声引起的。