Underwater wireless optical communication (UWOC) is useful for transmitting data short distances in the ocean. In most cases, such devices are placed on underwater vehicles to make it easier to establish a communication link. However, the vehicle often works in dark water. Thus it needs a light emitting diode (LED) as an illuminant for its camera to observe the surroundings, but this is noise to the UWOC system. Although such noise could be eliminated by inserting an optical filter in the UWOC receiver, the effectiveness depends on the incident angle of light into the filter. Because the illumination distribution of LED is quite complicated, there are some special requirements for UWOC systems to eliminate such noise. First, we simulate the incident angle distribution of LED illumination noise into the receivers of a bidirectional UWOC system with the Monte Carlo method. Then we analyze its influence to design an UWOC system. The results show that the wavelength of UWOC should be shorter than that of the LED illuminant to make them work simultaneously. Under the condition that the noise can be eliminated effectively, the spectrum width of the communication signal and the optical filter should be wider to enlarge the receiving field. According to the theoretical conclusion, we experimentally demonstrate a half-duplex UWOC system with an LED illuminant in dark water, where the attenuation coefficient is about 0.20 m − 1. In the system, each terminal has a white LED illuminant with 6.01 W optical power, a blue LED illuminant with 7.72 W optical power, and a UWOC transmitter based on a purple LED with about 1.25 W optical power. The UWOC realized a 27.78 Mbps rate and 19 m distance when the illuminants were open. The proposed UWOC system and its design criteria are useful for UWOC applications.

中文翻译：

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发光二极管照明噪声存在下半双工水下无线光通信实验演示

水下无线光通信（UWOC）可用于在海洋中短距离传输数据。在大多数情况下，此类设备被放置在水下航行器上，以便更容易建立通信链路。然而，车辆经常在黑暗的水中工作。因此，它需要一个发光二极管（LED）作为相机的光源来观察周围环境，但这对 UWOC 系统来说是噪音。尽管可以通过在 UWOC 接收器中插入光学滤波器来消除此类噪声，但其有效性取决于光进入滤波器的入射角度。由于LED的照度分布相当复杂，因此UWOC系统对消除此类噪声有一些特殊要求。第一的，我们使用蒙特卡罗方法模拟 LED 照明噪声进入双向 UWOC 系统接收器的入射角分布。然后我们分析其影响来设计UWOC系统。结果表明，UWOC的波长应比LED光源的波长短，才能使它们同时工作。在能够有效消除噪声的情况下，通信信号和光滤波器的频谱宽度应更宽，以扩大接收场。根据理论结论，我们在暗水中实验演示了一种采用LED光源的半双工UWOC系统，其衰减系数约为0.20 m − 1。系统中每个终端配备一个光功率为6.01 W的白光LED光源，光功率为 7.72 W 的蓝色 LED 光源，以及基于紫色 LED 的 UWOC 发射器，光功率约为 1.25 W。当光源打开时，UWOC 实现了 27.78 Mbps 的速率和 19 m 的距离。所提出的 UWOC 系统及其设计标准对于 UWOC 应用非常有用。