逼近香农极限的新型光调制技术

[摘要] 光传输技术经历了多代的技术演进发展，频谱效率得到了显著改善，业界开始探讨香农通信理论在光纤传输系统上的最基本线性和非线性信号通道容限是多少，从而使下一代的新技术超越当前100G相干系统的传输性能，进一步提升谱效率和总容量，以接近香农的理论极限。新技术包括了更复杂的调制码型和信道编解码方式、预滤波和其相结合的多符号同时检测算法、光正交频分复用（OFDM）和奈奎斯特波分复用（Nyquist WDM）的多载波技术以及抵抗非线性的补偿方案。新技术进一步优化后，很可能应用在超100G的光传输系统中，从而满足不断增长的带宽需求。

[关键词] 频谱效率；香农极限；高斯噪声；光信噪比；调制；非线性补偿

[Abstract] Optical transmission technologies have gone through several generations of development. Spectral efficiency has significantly improved, and industry has begun to seek the answer to a basic question: What are the fundamental linear and nonlinear signal channel limitations of Shannon theory when there is no compensation in optical fiber transmission systems? Next-generation technologies should exceed the 100G transmission capability of coherent systems in order to approach the Shannon limit. Spectral efficiency first needs to be improved before overall transmission capability can be improved. The means to improve spectral efficiency include more complex modulation formats and channel encoding/decoding algorithms, pre-filtering with multisymbol detection, optical OFDM and Nyquist WDM multicarrier technologies, and nonlinearity compensation. With further optimization, these technologies will most likely be incorporated into beyond-100G optical transport systems to meet bandwidth demand.

[Keywords] spectral efficiency; Shannon limit; Gaussian noise; optical signal noise ratio; modulation; nonlinearity compensation