Retro-Reflective Beam Communications with Spatially Separated Laser Resonator

TL;DR

This paper introduces a novel echo-interference-free resonant beam communication system using a spatially separated laser resonator with retro-reflective beam formation, enhancing high-speed optical wireless communication capabilities for 6G.

Contribution

It proposes a new RBCom system design based on second harmonic generation that eliminates echo interference and improves beamforming and alignment without complex controllers.

Findings

Achieves longer transmission distances beyond 10 Gbit/s.

Reduces beam diameter compared to existing OWC technologies.

Provides an analytical model for beam radius, power, and capacity.

Abstract

Optical wireless communications (OWC) utilizing infrared or visible light as the carrier attracts great attention in 6G research. Resonant beam communications (RBCom) is an OWC technology which simultaneously satisfies the needs of non-mechanical mobility and high signal-to-noise ratio~(SNR). It has the self-alignment feature and therefore avoids positioning and pointing operations. However, RBCom undergoes echo interference. Here we propose an echo-interference-free RBCom system design based on second harmonic generation. The transmitter and the receiver constitute a spatially separated laser resonator, in which the retro-reflective resonant beam is formed and tracks the receiver automatically. This structure provides the channel with adaptive capability in beamforming and alignment, which is similar to the concept of intelligent reflecting surface (IRS) enhanced communications, but without hardware and software controllers. Besides, we establish an analytical model to evaluate the beam radius, the beam power, and the channel capacity. The results show that our system achieves longer distance and smaller beam diameter for the transmission beyond 10 Gbit/s, compared with the existing OWC technologies.