Analyzing beam profile, intensity fluctuations, and beam wander with changing weather conditions on a free-space 1550 nm optical link path

Free-space optics holds the potential for data communications at high bandwidth and security while minimizing size, weight, and power. However, the effects of atmospheric turbulence on an optical beam limits and degrades communication performance and bit-error-rate. Although degradation of beam quality occurs due to many factors, typically unwanted aberrations due to fluctuations in the refractive index along beam path causing scattering, absorption, and beam wander is the main cause. Randomly distributed cells called eddies are formed in the propagation medium giving rise to turbulence as well. In our first study we characterized the beam on a 3-meter link in a laboratory environment. In this paper, we report experimental results with similar test conditions on a 50-meter FSO path and compare to the shorter path length results. We also correlate scintillation data to beam wander and spread. A phosphor-coated silicon CCD is used to record and study the beam’s intensity profile.