Zhang Xulun, Sun Peng, Xi Lixia, Zheng Zibo, Du Shucheng, Wei Jiacheng, Wu Yue, Zhang Xiaoguang
Opt Express. 2020 May 11;28(10):15360-15375. doi: 10.1364/OE.390293.
A nonlinear frequency division multiplexing (NFDM) transmission system, designed specifically for nonlinear fiber channel, has the potential to overcome the nonlinear Shannon capacity limit. However, the spectral efficiency (SE) of the current proven NFDM transmission systems is still lower than that of the analogous orthogonal frequency division multiplexing system. It is extremely necessary to explore effective modulation scheme for the aim of increasing the SE of NFDM system. In this study, we first propose the nonlinear-frequency-packing nonlinear frequency division multiplexing (NFP-NFDM) transmission system. In NFP-NFDM, the spacing of nonlinear subcarriers is squeezed and more nonlinear subcarriers can be packed, but the inter carrier interference (ICI) is introduced. The method of NFP in nonlinear Fourier domain is carefully designed to reduce the complexity of ICI cancellation. Through numerical simulation, we illustrate the feasibility of NFP-NFDM transmission, and higher SE in NFP-NFDM than that of NFDM system is also demonstrated. The upper bound of the normalized SE for NFP-NFDM is estimated, which is higher than that of current NFDM system. Besides, we find out that the NFP scheme may have the advantage of reducing the signal-noise interaction in fiber transmission scenario, which indicates there may be a better way to load the data into the nonlinear Fourier domain.
一种专门为非线性光纤信道设计的非线性频分复用（NFDM）传输系统，有潜力克服非线性香农容量限制。然而，当前已证实的NFDM传输系统的频谱效率（SE）仍低于类似的正交频分复用系统。为提高NFDM系统的SE，探索有效的调制方案极为必要。在本研究中，我们首先提出了非线性频率压缩非线性频分复用（NFP-NFDM）传输系统。在NFP-NFDM中，非线性子载波的间距被压缩，可容纳更多的非线性子载波，但会引入载波间干扰（ICI）。精心设计了非线性傅里叶域中的NFP方法，以降低ICI消除的复杂度。通过数值模拟，我们说明了NFP-NFDM传输的可行性，并且还证明了NFP-NFDM中的SE高于NFDM系统。估计了NFP-NFDM归一化SE的上限，其高于当前NFDM系统。此外，我们发现NFP方案在光纤传输场景中可能具有减少信号-噪声相互作用的优势，这表明可能存在一种更好的将数据加载到非线性傅里叶域的方法。
