Characterization of noise regimes in Mid-IR free-space optical communication based on quantum cascade lasers

TL;DR

This paper experimentally characterizes noise regimes in Mid-IR free-space optical communication using quantum cascade lasers, revealing two distinct noise regions and potential for error-free links up to 8 km in adverse conditions.

Contribution

It provides the first detailed experimental analysis of noise regimes in Mid-IR FSO systems based on QCLs, linking laboratory results with atmospheric models.

Findings

Two distinct noise regimes identified in Mid-IR FSO links.

Error-free communication possible up to 8 km in low visibility conditions.

Experimental results align with atmospheric loss predictions.

Abstract

The recent development of Quantum Cascade Lasers (QCLs) represents one of the biggest opportunities for the deployment of a new class of Free Space Optical (FSO) communication systems working in the mid-infrared (Mid-IR) wavelength range. As compared to more common FSO systems exploiting the telecom range, the larger wavelength employed in Mid-IR systems delivers exceptional benefits in case of adverse atmospheric conditions, as the reduced scattering rate strongly suppresses detrimental effects on the FSO link length given by the presence of rain, dust, fog and haze. In this work, we use a novel FSO testbed operating at \SI{4.7}{\micro m}, to provide a detailed experimental analysis of noise regimes that could occur in realistic FSO Mid-IR systems based on QCLs. Our analysis reveals the existence of two distinct noise regions, corresponding to different realistic channel attenuation conditions, which are precisely controlled in our setup. To relate our results with real outdoor configurations, we combine experimental data with predictions of an atmospheric channel loss model, finding that error-free communication could be attained for effective distances up to 8~km in low visibility conditions of 1 km. Our analysis of noise regimes may have a key relevance for the development of novel, long-range FSO communication systems based on Mid-IR QCL sources