Atmospheric Aerial Optical Links: Assessing Channel Constraints for Stable Long-Range Communications—A Historical Perspective

New-generation communications aim for ubiquitous and pervasive communications with high data rates. Electromagnetic spectrum saturation and increasing data volumes can employ the use of free-space optical communication to ease capacity loads in modern networks. In this writing, we review the impact of the atmospheric channel on the optical signal dynamics for long-range data links between high-speed and maneuverability suborbital platforms in full atmosphere. This work presents the main propagation constraints, such as path loss, turbulence, and aero-optics, which are environment-dependent and geometry-dependent for this worst-case scenario. To carry out our study, we recall experimental results collected in the literature since the early times, showing system constraints and performance limits. This provides a historical timeline perspective. Theoretical models and channel management techniques that appeared through time are briefly summarized, and their impact on link budget and stability on reference link geometries is addressed through analytical simulation. In conclusion, this paper shows that an integrated approach to this kind of link is successful mainly with a convergence of mitigation techniques and tailored engineering, which cannot neglect the knowledge of the operating environment and strongly relies on accurate physics modeling, which remains an area of active open research.