A comprehensive comparison between Terahertz and optical wireless communications

This paper presents a comprehensive quantitative comparison between Terahertz (THz) communication and optical wireless communication (OWC) technologies, with a focus on indoor and outdoor deployment scenarios. For indoor environments, we compare THz and vertical-cavity surface-emitting laser (VCSEL)-based OWC systems by incorporating misalignment effects using a multi-ray THz channel model with antenna patterns and a Gaussian beam model for VCSELs. Unified beamwidth assumptions enable consistent evaluation. We further develop power consumption models capturing THz phase noise, VCSEL nonlinearities, and photodetector bandwidth-area tradeoffs, facilitating a detailed energy efficiency analysis under multi-transmitter coverage. For outdoor scenarios, we survey existing stochastic channel models that characterize path loss, pointing errors, and small-scale fading for both THz and free space optics (FSO) links. These models are applied to unmanned aerial vehicle (UAV)-based use cases to evaluate communication robustness under dynamic conditions. Our findings highlight critical performance tradeoffs and deployment challenges, offering insights into the relative advantages of THz and OWC technologies in diverse environments.