Comparative analysis of atmospheric turbulence-induced laser power fluctuations in a monolithic and tiled optical receiver system
Date of Award
M.S. in Electro-Optics and Photonics
Department of Electro-Optics and Photonics
This research project compares the performance of a Monolithic Optical Receiver and a Multi Aperture Receiver, in order to reduce optical power fluctuations induced by a Gaussian beam traveling through atmospheric turbulence. In this this work a mathematical model to describe the effects of focal spot wander and aperture averaging is provided, in order to explain the reduction of scintillation by increasing the area of an optical receiver. In particular, the Churnside model is used due to its simplicity to describe the effect of aperture averaging as a function of the collection diameter for receiving optical systems. In other hand, the steps for the alignment of Multi Aperture Receiver systems are shown. In this section, interferometric tests are used to align each aperture of this optical receiver system, and thereby achieve a correct multimode fiber optic coupling of the Gaussian beam received after propagating through atmospheric turbulence. At the same time, a finder scope is attached, which aims to align the multi aperture receiver system with the optical axis of the Gaussian beam propagated through an atmospheric channel. iv This work proposes a set of five experiments which use the normalized variance of the received power as a figure of merit, to compare the fluctuations of power received with both optical collectors in different conditions of atmospheric turbulence. The atmospheric channel used in practice is described in detail, and consists of a 7km optical path in the city of Dayton Ohio, which is subjected to tests in different conditions of atmospheric turbulence, that changes depending on the time of day in which measurements are done. In the case of the Multi Aperture Receiver system, it has been possible to define an effective diameter to compare the increase in sub-apertures with the increase in the total diameter of a monolithic system. With this, it has been possible to introduce a new concept called "sub-apertures averaging", referring to the classical theory of aperture averaging, applied to Multi Aperture Receiver systems. Finally, in this work a method is proposed to find the transverse wind speed in atmospheric channels, using the cross-correlation function between the power time series measured in two of the sub-apertures of the Multi Aperture Receiver system.
Optics, Atmosphere, Atmospheric Sciences, Free Space Optical Communications
Copyright © 2021, author.
Valero, Marcos E., "Comparative analysis of atmospheric turbulence-induced laser power fluctuations in a monolithic and tiled optical receiver system" (2021). Graduate Theses and Dissertations. 7069.