Wireless power transfer (WPT) is a promising solution to provide convenientand perpetual energy supplies to electronics. Traditional WPT technologies facethe challenge of providing Watt-level power over meter-level distance forInternet of Things (IoT) and mobile devices, such as sensors, controllers,smart-phones, laptops, etc.. Distributed laser charging (DLC), a new WPTalternative, has the potential to solve these problems and enable WPT with thesimilar experience as WiFi communications. In this paper, we present amulti-module DLC system model, in order to illustrate its physical fundamentalsand mathematical formula. This analytical modeling enables the evaluation ofpower conversion or transmission for each individual module, considering theimpacts of laser wavelength, transmission attenuation and photovoltaic-cell(PV-cell) temperature. Based on the linear approximation ofelectricity-to-laser and laser-to-electricity power conversion validated bymeasurement and simulation, we derive the maximum power transmission efficiencyin closed-form. Thus, we demonstrate the variation of the maximum powertransmission efficiency depending on the supply power at the transmitter, laserwavelength, transmission distance, and PV-cell temperature. Similar to themaximization of information transmission capacity in wireless informationtransfer (WIT), the maximization of the power transmission efficiency isequally important in WPT. Therefore, this work not only provides the insight ofDLC in theory, but also offers the guideline of DLC system design in practice.
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