Cheng Chen, Li Xueyang, Xiang Qian, Li Jun, Jin Yongchao, Wei Zixian, Fu H Y, Yang Yanfu
Opt Express. 2022 Jul 18;30(15):28014-28023. doi: 10.1364/OE.462259.
Low-cost underwater wireless optical communication (UOWC) systems are attractive for high-speed connections among unmanned vehicles or devices in various underwater applications. Here we demonstrate a high-speed and low-cost UOWC system using a low-resolution digital to analog converter (DAC), a single-pixel mini-sized light-emitting diode (mini-LED), and digital pre-compensation (DPC). The enabled DPC scheme comprises digital pre-distortion (DPD), digital pre-emphasis (DPE), and digital resolution enhancer (DRE), which pre-compensate for mini-LED nonlinearity, the bandwidth limitation of the mini-LED and avalanche photodiode detector, and DAC resolution limitation, respectively. The simulation results show that the in-band signal-to-quantization noise ratio can be increased by 6.8 dB using DRE based on a 4-bit DAC. To further improve the system capacity, we tune the level of DPE in order to optimize the trade-off between the residual inter-symbol interference and signal-to-noise ratio. With the combination of optimized DPE and DRE, we obtain a 21.1% higher data rate compared with full DPE only and demonstrate the transmission of 6.9 Gb/s PAM-8 signal over a 2-m distance underwater based on a single-pixel mini-LED and 4-bit DAC. This paper reports a cost-effective UOWC system first using a low-resolution DAC and DPC, which offers a promising path toward low-cost underwater optical wireless networks.
低成本水下无线光通信（UOWC）系统对于各种水下应用中无人车辆或设备之间的高速连接具有吸引力。在此，我们展示了一种高速且低成本的UOWC系统，该系统使用低分辨率数模转换器（DAC）、单像素微型发光二极管（mini-LED）和数字预补偿（DPC）。启用的DPC方案包括数字预失真（DPD）、数字预加重（DPE）和数字分辨率增强器（DRE），它们分别对mini-LED的非线性、mini-LED和雪崩光电二极管探测器的带宽限制以及DAC分辨率限制进行预补偿。仿真结果表明，基于4位DAC使用DRE可使带内信号与量化噪声比提高6.8 dB。为了进一步提高系统容量，我们调整DPE的电平，以优化残余符号间干扰与信噪比之间的权衡。通过优化的DPE和DRE相结合，与仅使用全DPE相比，我们获得了高21.1%的数据速率，并基于单像素mini-LED和4位DAC在水下2米距离上演示了6.9 Gb/s PAM-8信号的传输。本文首次报道了一种使用低分辨率DAC和DPC的经济高效的UOWC系统，为低成本水下光无线网络提供了一条有前景的途径。
