Re-configurable Intelligent Surface-based VLC Receivers Using Tunable Liquid-crystals: The Concept

TL;DR

This paper introduces a novel use of liquid crystal-based re-configurable intelligent surfaces to enhance VLC signal detection and extend transmission range, demonstrating significant improvements through experimental analysis.

Contribution

It proposes the first application of LC-based RIS in VLC systems, showing how tunable liquid crystals can amplify signals and increase transmission distances.

Findings

VLC transmission range improved by 0.20 to 1.08 meters with LC and dye.

Maximum range extension of 6.56 meters with specific dye concentrations.

LC-based RIS effectively enhances VLC signal detection and range.

Abstract

Visible light communication (VLC) enables access to huge unlicensed bandwidth, a higher security level, and no radio frequency interference. With these advantages, VLC emerges as a complementary solution to radio frequency communications. VLC systems have primarily been designed for indoor scenarios with typical transmission distances between 2 and 5 m. Different designs would be required for larger distances. This paper proposes for the first time the use of a liquid crystal (LC)-based re-configurable intelligent surface (RIS) on improving the VLC signal detection and transmission range. An LC-based RIS presents multiple advantages, including the tunability of its photo-refractive parameters. Another advantage is its light amplification capabilities when under the influence of an externally applied field. In this paper, we analyze an LC-based RIS structure to amplify the detected light and improve the VLC signal detection and transmission range. Results show that mixing LC with 4 to 8 wt\% concentration of a dye such as the terthiophene (3T-2MB) improves the VLC transmission range of about 0.20 to 1.08 m. This improvement can reach 6.56 m if we combine 8 wt\% concentration of 3T-2MB and 0.1 wt\% concentration of trinitrofluorenone.