Underwater wireless optical communication (UWOC) has attracted increasing interest in various underwater activities because of its order-of-magnitude higher bandwidth compared to acoustic and radio-frequency technologies. Testbeds and pre-aligned UWOC links were constructed for physical layer evaluation, which verified that UWOC systems can operate at tens of gigabits per second or close to a hundred meters of distance. This holds promise for realizing a globally connected Internet of Underwater Things (IoUT). However, due to the fundamental complexity of the ocean water environment, there are considerable practical challenges in establishing reliable UWOC links. Thus, in addition to providing an exhaustive overview of recent advances in UWOC, this article addresses various underwater challenges and offers insights into the solutions. In particular, oceanic turbulence, which induces scintillation and misalignment in underwater links, is one of the key factors in degrading UWOC performance. Novel solutions are proposed to ease the requirements on pointing, acquisition, and tracking (PAT) for establishing robustness in UWOC links. The solutions include light-scattering-based non-line-of-sight (NLOS) communication modality as well as PAT-relieving scintillating-fiber-based photoreceiver and large-photovoltaic cells as the optical signal detectors. Naturally, the dual-function photovoltaic–photodetector device readily offers a means of energy harvesting for powering up the future IoUT sensors.

中文翻译：

---

水下无线光通信实际考虑及解决方案综述

水下无线光通信 (UWOC) 与声学和射频技术相比，其带宽数量级更高，因此对各种水下活动越来越感兴趣。为物理层评估构建了测试台和预对齐的 UWOC 链路，这验证了 UWOC 系统可以以每秒数十吉比特或接近百米的距离运行。这有望实现全球连接的水下物联网 (IoUT)。然而，由于海洋水环境的基本复杂性，在建立可靠的 UWOC 链接方面存在相当大的实际挑战。因此，除了详尽概述 UWOC 的最新进展外，本文还解决了各种水下挑战并提供了对解决方案的见解。特别是，海洋湍流会导致水下链路中的闪烁和错位，是降低 UWOC 性能的关键因素之一。提出了新的解决方案，以减轻对指向、捕获和跟踪 (PAT) 的要求，以便在 UWOC 链路中建立稳健性。这些解决方案包括基于光散射的非视距 (NLOS) 通信模式以及基于 PAT 的闪烁光纤光接收器和作为光信号检测器的大型光伏电池。自然地，双功能光伏-光电探测器器件很容易提供一种能量收集手段，为未来的 IoUT 传感器供电。提出了新的解决方案，以减轻对指向、捕获和跟踪 (PAT) 的要求，以便在 UWOC 链路中建立稳健性。这些解决方案包括基于光散射的非视距 (NLOS) 通信模式以及基于 PAT 的闪烁光纤光接收器和作为光信号检测器的大型光伏电池。自然地，双功能光伏-光电探测器器件很容易提供一种能量收集手段，为未来的 IoUT 传感器供电。提出了新的解决方案，以减轻对指向、捕获和跟踪 (PAT) 的要求，以便在 UWOC 链路中建立稳健性。这些解决方案包括基于光散射的非视距 (NLOS) 通信模式以及基于 PAT 的闪烁光纤光接收器和作为光信号检测器的大型光伏电池。自然地，双功能光伏-光电探测器器件很容易提供一种能量收集手段，为未来的 IoUT 传感器供电。