Probabilistic constellation shaping is investigated in the context of nonlinear fiber optic communication channels. Based on a general framework, different link types are considered—1. dispersion-managed channels, 2. unrepeatered transmission channels and 3. ideal distributed Raman amplified channels. These channels exhibit nonlinear effects to a degree that conventional probabilistic constellation shaping strategies for the additive white Gaussian (AWGN) noise channel are suboptimal. A channel-agnostic optimization strategy is used to optimize the constellation probability mass functions (PMFs) for the channels in use. Optimized PMFs are obtained, which balance the effects of additive amplified spontaneous emission noise and nonlinear interference. The obtained PMFs cannot be modeled by the conventional Maxwell-Boltzmann PMFs and outperform optimal choices of these in all the investigated channels. Suboptimal choices of constellation shapes are associated with increased nonlinear effects in the form of non-Gaussian noise. For dispersion-managed channels, a reach gain in 2 spans is seen and across the three channel types, gains of >0.1 bits/symbol over unshaped quadrature-amplitude modulation (QAM) are seen using channel-optimized probablistic shaping.

中文翻译：

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具有非高斯噪声的非线性光纤通道的概率整形优化

在非线性光纤通信信道的背景下研究了概率星座整形。基于一个通用框架，考虑了不同的链接类型——1。色散管理通道，2. 无中继传输通道和 3. 理想的分布式拉曼放大通道。这些通道在一定程度上表现出非线性效应，以至于用于加性白高斯 (AWGN) 噪声通道的常规概率星座整形策略是次优的。信道不可知优化策略用于优化所用信道的星座概率质量函数 (PMF)。获得优化的 PMF，它平衡了加性放大自发辐射噪声和非线性干扰的影响。获得的 PMF 不能由传统的 Maxwell-Boltzmann PMF 建模，并且在所有研究的通道中都优于这些的最佳选择。星座形状的次优选择与非高斯噪声形式的非线性效应增加有关。对于色散管理信道，可以看到 2 个跨度的到达增益，并且在三种信道类型中，使用信道优化的概率整形可以看到超过未成形正交幅度调制 (QAM) 的 >0.1 比特/符号的增益。