A combination of scattering and scintillation effects is considered to compare the resilience of mid-IR and near-IR free space communication links. Beam-wander r_w(t) under different scintillation conditions for mid-IR and near- IR beams are recorded simultaneously in real-time by a unique broad-band camera. The correlation coefficients show that both beams undergo the same pathway and experience the same scattering and scintillation effect which allows to identify and distill wavelength dependent effects. Using the frequency dependence in the observed beam wander allows for classification of our simulated atmospheric turbulence. Under these lab conditions, perceived refractive index structure parameter C_n^2 is extracted for each wavelength and a long-term radius is estimated for a long-distance link. In addition, the transmissivity and broadening of beams are calculated using discrete ordinate method to account for the scattering by fog. Considering both scattering and scintillation effects, the experimental and analytical results show that mid-IR (4.328 μm) beam has higher resilience in low visibility conditions compared to a near-IR (1.550 μm) beam.

Date Published: 4 March 2019
PDF: 6 pages
Proc. SPIE 10910, Free-Space Laser Communications XXXI, 1091024 (4 March 2019); doi: 10.1117/12.2513941

Published in SPIE Proceedings Vol. 10910:
Free-Space Laser Communications XXXI
Hamid Hemmati; Don M. Boroson, Editor(s)