Probabilistic amplitude shaping (PAS) is a practical means to achieve a shaping gain in optical fiber communication. However, PAS and shaping in general also affect the signal-dependent generation of nonlinear interference. This provides an opportunity for nonlinearity mitigation through PAS, which is also referred to as a nonlinear shaping gain. In this paper, we introduce a linear lowpass filter model that relates transmitted symbol-energy sequences and nonlinear distortion experienced in an optical fiber channel. Based on this model, we conduct a nonlinearity analysis of PAS with respect to shaping blocklength and mapping strategy. Our model explains results and relationships found in literature and can be used as a design tool for PAS with improved nonlinearity tolerance. We use the model to introduce a new metric for PAS with sequence selection. We perform simulations of selection-based PAS with various amplitude shapers and mapping strategies to demonstrate the effectiveness of the new metric in different optical fiber system scenarios.

翻译：概率幅度整形是光纤通信中实现整形增益的实用手段。然而，概率幅度整形及一般意义上的整形也会影响信号相关的非线性干扰生成。这为通过概率幅度整形实现非线性缓解提供了契机，此效应亦称为非线性整形增益。本文提出一种线性低通滤波器模型，该模型建立传输符号能量序列与光纤信道中非线性畸变之间的关联。基于该模型，我们从整形块长与映射策略两个维度对概率幅度整形进行非线性分析。该模型能解释既有文献中的实验结果与关联规律，并可作为提升概率幅度整形非线性容忍度的设计工具。我们利用该模型提出一种面向序列选择的概率幅度整形新度量。通过采用不同幅度整形器与映射策略的基于选择的概率幅度整形仿真，我们验证了新度量在不同光纤通信系统场景中的有效性。