Abstract
Propagation through turbulent media produces complex amplitude fluctuations and temporal spreading of narrow optical pulses. Light-absorbing aerosols present in the atmospheric transmission path will perturb the refractive index structure parameter (Cn2) through atmospheric heating. The consequent enhancement in broadening and attenuation of ultrashort (femtosecond) optical pulses has been calculated by combining multi-satellite observations, radiosonde profiles and computational radiative transfer. It is shown that narrower optical pulses are more vulnerable to aerosol-induced impairments while broader pulses are more resilient, notwithstanding three to four orders of enhanced optical scintillation.
Highlights
Data carrying potential of optical communication links has increased significantly in the past two decades
Despite possessing the potential to replace existing radio frequency (RF) systems, Free-Space Optical (FSO) links are susceptible to atmospheric turbulence effects such as optical scintillation, pulse broadening, beam wandering etc. and signal loss resulting from the light absorption and scattering produced by atmospheric aerosols [1,2,3]
It readily emerges that as the initial pulse width decreases below 90 fs, the third-order dispersion effects start contributing and below 40 fs become too high that pulses with lesser width cannot be used for practical FSO communication systems
Summary
Data carrying potential of optical communication links has increased significantly in the past two decades. FSO communication systems exploit different beam shapes and ultrashort pulses due to their potential ability to resist detrimental influence of atmospheric channel effects such as convective turbulence and atmospheric extinction. Aerosol black carbon (BC, called as soot), originating from the incomplete combustion of carbonaceous fuels and injected into the atmosphere, significantly contribute to the absorption of solar radiation owing to its broad-band absorption in the visible and near-infrared spectra [8] These highly absorbing aerosols are known to produce substantial heating of the lower atmosphere, where they are abundant [8,9]. It is reported that increased loading of BC aerosols in the atmospheric channel results in significant signal deterioration during stable atmospheric conditions [18] by significantly degrading the bit error rate (BER) performance of FSO communication links [19] and the horizontal propagation of optical signals experience varied extinction due to the presence of humid aerosols [20]. We study the problem of propagation of ultrashort optical pulses through turbulent atmosphere and its additional broadening and energy redistribution due to the radiative effects of aerosol particles through thermodynamic observations and radiative transfer theory
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