An atmospheric turbulence, scattering, and weather monitoring system for three kilometers, partially over water path for monitoring the statistics of turbulence

Abstract

So-called "free-space" laser communication systems working near the surface of the Earth must operate in the presence of atmospheric turbulence. The effects of the atmospheric turbulence on the laser beam which are relevant to optical communications are a broadening of the laser footprint, random jitter of the laser beam, and high spatial frequency intensity fluctuations referred to as scintillation. The overall goal of our program is to improve performance and extend the range of optical communications systems by exploring the use of adaptive optics and channel coding. To better model the performance of a real system operating in the real world, we have developed an outdoor turbulence-measurement and monitoring system. In this paper we describe an atmospheric turbulence monitoring system for three kilometers, partially over water path. The laser transmitter operates at 808 nm with a source power of 2mW. The receiver consists of relay optics, a Hartmann wave front sensor (WFS), and a CCD camera. The WFS is used to monitor atmospheric turbulence-induced phase aberrations, and the camera is used for both conventional imaging studies and measurements of anisoplanatic effects. In this paper we describe this system and present some preliminary results obtained from the measurements. Show more