Chinese Optics Letters, Vol. 17, Issue 10, 100012 (2019)
High-speed underwater wireless optical communications: from a perspective of advanced modulation formats [Invited]
Chao Fei1,2, Xiaojian Hong1,2, Ji Du1,2, Guowu Zhang1,2, Yuan Wang1,2, Xiaoman Shen1,2, Yuefeng Lu1,2, Yang Guo1,2, and Sailing He1,2,*
- 1Centre for Optical and Electromagnetic Research, National Engineering Research Center for Optical Instruments, Zhejiang University, Hangzhou 310058, China
- 2Ningbo Research Institute, Zhejiang University, Ningbo 315100, China
In this paper, recent advances in underwater wireless optical communication (UWOC) are reviewed for both LED- and LD-based systems, mainly from a perspective of advanced modulation formats. Volterra series-based nonlinear equalizers, which can effectively counteract the nonlinear impairments induced by the UWOC system components, are discussed and experimentally demonstrated. Both the effectiveness and robustness of the proposed Volterra nonlinear equalizer in UWOC systems under different water turbidities are validated. To further approach the Shannon capacity limit of the UWOC system, the probabilistic constellation shaping technique is introduced, which can overcome the inherent gap between a conventional regular quadrature amplitude modulation (QAM) format and the Shannon capacity of the channel. The experimental results have shown a significant system capacity improvement compared to the cases using a regular QAM.