C2n Modeling for Free-Space Optical Communications: A Review

Abstract

Atmospheric turbulence influence on optical wave propagation, referred to as optical turbulence, has long been studied for astronomical applications and is now being addressed for free-space optical communication links between ground and satellites. While challenges overlap, models developed for astronomical applications are not fully transferable to optical communications. This paper provides a literature review of optical turbulence models, i.e., models giving vertical profiles of the refractive index structure parameter C2n, highlighting differences between astronomical and optical communication sites. It presents different classifications of available C2n models, based on the atmospheric layer they target and their necessary input parameters. Boundary layer C2n models are also addressed, and recent machine learning approaches for C2n modeling are discussed. Additionally, commonly used metrics for comparing C2n profiles are introduced. Therefore, this work provides important insights into optical turbulence model selection, enabling accurate site characterization and informed optical terminal design.