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Quantification of turbulence by the Equivalent Temperature Gradient
Kovaľová, Alžbeta ; Látal,, Jan (referee) ; Hudcová, Lucie (advisor)
The diploma thesis is focused on the optical beam propagating in the atmosphere in a wireless communication optical link. The first part of the work explains the atmospheric transmission media with turbulence and its effects on reliability of the optical system. The second part introduces methods for turbulence determination based on a statistical approach to turbulence quantification are introduced. In the third part, method of equivalent temperature gradient is described with the advantage of immediate turbulence evaluation. The output of this thesis is the model of turbulent environment formed by the optical elements. Analysis of turbulent properties and non-reciprocal nature of turbulent channel is processed by a 2D simulator based on the mentioned model and method of equivalent temperature gradient.
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Interferometric measurement of optical signal in turbulence
Kovaľová, Soňa ; Křivák,, Petr (referee) ; Hudcová, Lucie (advisor)
The aim of this thesis is to quantify the impact of atmospheric turbulence on optical signal used in free space optic communication systems. The first part is associated with atmosphere as transmission medium. Following part deals with interferometry and components of interferometers. Various methods of analysis of trasmission environment for optical beam are introduced theoretically and experimentally. Mathematical apparatus based on Kolmogorov’s cascade theory, Rytov’s variance was used to find value of structural parameter of refraction as a main measure of turbulence intensity. Experimentally obtained data were subjected to statistical analysis. The visualization of interference pattern fluctuations under turbulent conditions is shown in the last section. Interferometric method was realized with Michelson interferometer.
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Communication protocols for Free-Space Optical links
Šedo, Ondrej ; Kincl, Zdeněk (referee) ; Kolka, Zdeněk (advisor)
This master’s thesis is focused on behaviour of the TCP/IP protocol on free-space optical link which is affected by the effect of atmospheric turbulence. This causes fluctuation of the received optical power and therefor bit error rate changes. In the simulation model short-time bit error rate is calculated from random generated received optical signal and then used in time-domain analysis of the OMNeT++ network simulator. A buffer in transmitter is designed based on simulation results. It pauses the data transmitting in cases of FSO link outage. This method is then implemented into FPGA device.
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Complex turbulent model for various cells dimensions
Maluš, Miroslav ; Kyselák,, Martin (referee) ; Hudcová, Lucie (advisor)
This diploma thesis is about creating a program to model turbulent cells of different sizes on the chosen transmission path. The initial part of the work is devoted to the formation of atmospheric turbulence and the mathematical description of the extent of turbulence and its effect on optical waves. The methods of the turbulence generation and their physical description of formation are described below. The practical part is devoted to the created program in the MATLAB.
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The distribution of relative variance of optical intensity in laser beam
Barcík, Peter ; Coufalíková,, Aneta (referee) ; Hudcová, Lucie (advisor)
This master´s thesis provides basic properties and measurement of optical beams. In the first chapter is shown division of light on ray, wave and beam optics. Atmospheric optics and properties associated with propagation of light through the earth's atmosphere is presented in the second chapter. In the third part are shown basic techniques for Gaussian beam shaping. The last chapter deals with measurement of optical beam after propagating through a turbulent medium. In this section is shown distribution of relative variance of optical intensity in Gaussian and Top-Hat beam. There is also measured spatial coherence of laser beam in the turbulent atmospheric transmission media. Finally effect of the beam wander is investigated.
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Influence of atmospheric turbulences on laser beam intensity profile
Císař, David ; Wilfert, Otakar (referee) ; Hudcová, Lucie (advisor)
Free space optical communications provide a reliable alternative to microwave and cable system applications. This technology is utilized for an optical links between ground stations, and moreover for links between High Altitude Platforms (HAPs). The main goal of the project is to gather knowledge about degradation of an optical beam in the atmosphere. The optical beam is being exposed to many factors such as intensity fluctuation based on turbulence, attenuation due to absorption and scattering. Furthermore, an emergence and influence of the atmospheric turbulences on the intensity profile of the laser beam are discussed. At the end, the methods of atmospheric turbulence measurement are given.
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Influence of atmospheric turbulences on the optical beam
Bárta, Miroslav ; Wilfert, Otakar (referee) ; Hudcová, Lucie (advisor)
The aim of this thesis is to study a free space optics and its application in communication technologies. It describes possible interrupting impacts on the beamed optical signal, which are signal noise, attenuation of the atmosphere and atmospheric turbulence. The basis of the thesis is to describe the impact of the atmospheric turbulences on the optical beam. Fluctuation of optical intensity in the optical beam has been measured and index of refraction structure parameter calculated. With its assistance, turbulence rate has been determined.
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Prediction of the atmospheric turbulence
Sloboda, Šimon ; Barcík, Peter (referee) ; Hudcová, Lucie (advisor)
The aim of this work is to examine theoretical knowledge of the refractive index structure parameter and models for its calculation and prediction. Based on data downloaded from meteorological services, the accuracy of refractive index structure parameter prediction using Sadot-Kopeika model was evaluated at ten different locations on Earth. A program was created for the calculation and prediction of the refractive index structure parameter, which uses downloaded meteorological data.
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