In this paper, we study optical simultaneous wireless information and power transfer (SWIPT) systems, where a photovoltaic optical receiver (RX) is illuminated by ambient light and an intensity-modulated free space optical (FSO) signal. To facilitate simultaneous information reception and energy harvesting (EH) at the RX, the received optical signal is first converted to an electrical signal, and then, its alternating current (AC) and direct current (DC) components are separated and utilized for information decoding and EH, respectively. By accurately analysing the equivalent electrical circuit of the photovoltaic RX, we model the current flow through the photovoltaic p-n junction in both the low and high input power regimes using a two-diode model of the p-n junction and we derive a closed-form non-linear EH model that characterizes the harvested power at the RX. Furthermore, taking into account the non-linear behaviour of the photovoltaic RX on information reception, we derive the optimal distribution of the transmit information signal that maximizes the achievable information rate. The proposed EH model is validated by circuit simulation results. Furthermore, we compare with two baseline models based on maximum power point (MPP) tracking at the RX and a single-diode p-n junction model, respectively, and demonstrate that in contrast to the proposed EH model, they are not able to fully capture the non-linearity of photovoltaic optical RXs. Finally, our numerical results highlight that the proposed optimal distribution of the transmit signal yields significantly higher achievable information rates compared to uniformly distributed transmit signals, which are optimal for linear optical information RXs.

翻译：本文研究光学同步无线信息和功率传输(SWIPT)系统，其中光伏光学接收器(RX)同时受到环境光照和强度调制的自由空间光(FSO)信号照射。为在接收端实现信息接收与能量收集(EH)的协同工作，接收到的光信号首先转换为电信号，随后其交流(AC)和直流(DC)分量被分离并分别用于信息解码和能量收集。通过精确分析光伏接收器的等效电路，我们采用p-n结双二极管模型对低输入功率和高输入功率两种场景下的光伏p-n结电流进行建模，并推导出表征接收端收集功率的闭式非线性能量收集模型。进一步考虑光伏接收器非线性特性对信息接收的影响，我们推导出使可达信息速率最大化的发射信息信号最优分布。所提能量收集模型通过电路仿真结果进行了验证。此外，我们与两种基线模型(分别基于接收端最大功率点(MPP)跟踪和p-n结单二极管模型)进行对比，结果表明与所提模型不同，它们无法完全捕捉光伏光学接收器的非线性特性。最后，数值结果指出，与均匀分布发射信号(线性光学信息接收器的最优信号)相比，所提出的发射信号最优分布能显著提升可达信息速率。