Achieving higher spectral efficiency is an efficient approach to address the bandwidth crisis of optical networks, but it faces significant technical challenges. High-spectral-efficiency non-orthogonal frequency-division multiplexing (NOFDM) has been proposed for meeting the requirement of optical networks' capacity upgrade. Compared to orthogonal frequency-division multiplexing, NOFDM can achieve higher spectral efficiency by compressing the subcarrier spacing narrower than the Nyquist orthogonal spacing, but this inevitably induces inter-carrier interference (ICI). ICI cancellation algorithms are crucial in NOFDM for correctly recovering the transmitted signal at the expense of extra processing power. Nowadays, processing power is no longer the obstacle to eliminate ICI due to the rapid development of application-specific integrated circuits for efficient implementation of digital signal processing. In this article, fast multiplexing and demultiplexing for NOFDM are implemented based on inverse fast Fourier transform and fast Fourier transform, respectively. Meanwhile, three representative ICI cancellation algorithms are discussed, and one of them is experimentally implemented. Furthermore, we propose non-orthogonal discrete multitone (NODMT) by integrating the advantages of NOFDM and DMT, which has the potential to achieve improved spectral efficiency for future optical networks.

中文翻译：

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非正交离散多音：提高光网络的频谱效率


实现更高的频谱效率是解决光网络带宽危机的有效方法，但它面临着重大的技术挑战。为了满足光网络容量升级的要求，高频谱效率非正交频分复用(NOFDM)被提出。与正交频分复用相比，NOFDM可以通过将子载波间隔压缩得比奈奎斯特正交间隔更窄来实现更高的频谱效率，但这不可避免地会引起载波间干扰（ICI）。 ICI 消除算法在 NOFDM 中至关重要，它可以以额外的处理能力为代价正确恢复传输的信号。如今，由于用于高效实现数字信号处理的专用集成电路的快速发展，处理能力不再是消除ICI的障碍。本文分别基于快速傅里叶逆变换和快速傅里叶变换实现了NOFDM的快速复用和解复用。同时，讨论了三种具有代表性的ICI消除算法，并对其中一种进行了实验实现。此外，我们通过整合NOFDM和DMT的优点提出了非正交离散多音（NODMT），它有可能提高未来光网络的频谱效率。