Optical Communications for High-Altitude Platforms

TLDR

This paper reviews technologies, theoretical studies, and experimental field trials for optical communications to and from high‑altitude platforms. The authors discuss pointing, acquisition, and tracking of laser terminals, low‑divergence beam transmission at multi‑Gbps, atmospheric and background light effects, flight qualification constraints, and mitigation techniques such as forward‑error correction, adaptive optics, and diversity reception. These measures can raise data rates or link distances while maintaining low bit‑error ratios and outage probabilities, though free‑space optical rates remain below terrestrial fiber capabilities.

Abstract

This paper contains a review of technologies, theoretical studies, and experimental field trials for optical communications from and to high-altitude platforms (HAPs). We discuss the pointing, acquisition, and tracking of laser terminals and describe how laser beams with low divergence can be used to transmit data at multi-Gigabits per second. Investigating the influence of the atmosphere, background light, and flight qualification requirements on system design, we explain why the data rates in free-space optical communications are still significantly below those possible in today's terrestrial fiber-based systems. Techniques like forward-error correction, adaptive optics, and diversity reception are discussed. Such measures help to increase the data rate or link distance while keeping the bit error ratio and outage probability of the optical HAP communication system low.