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Longitudinal structures in optical fibres with the use in sensorics
Falešník, Vlastimil ; Čučka, Milan (referee) ; Urban, František (advisor)
This semestral work describes key concepts, principles and basic characteristics of optical fibers. Furthermore, the principles of phase mask and subsequent records of perpendicular or tilted structures in fiber are being discussed. The work also introduces the use of such structures in sensorics as well as its connection to Bragg grating. Considerable part of this thesis is dedicated to analysis and production of longitudinal structures in fibers.
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Apodization of the fibre Bragg gratings by use of phase mask UV exposition
Burian, Tomáš ; Hejátková, Edita (referee) ; Urban, František (advisor)
This thesis describes the problem of fiber gratings, focusing primarily on the use of Bragg's grids in the sensor. It describes the types of fiber mesh production, especially the method of writing with a phase mask. The next part deals with the possibilities of using apodization in fiber optic systems. It deals with the various functions that can be used to describe apodization. The following part describes the moire principle, especially the method of overlapping two phase masks with a different period.
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Dispersion measurements of optical transmissions.
Motúz, Rastislav ; Urban, František (referee) ; Filka, Miloslav (advisor)
This thesis firstly theoretically describes phenomena which appear in optical fiber transmission. The theoretical part of the thesis deals with linear and non-linear phenomena, and later on proceeds to dispersions with a more significant effect on the optical transmission quality. It puts polarization to the centre of the phenomenon called Polarization mode dispersion (PMD), which is the main object of our interest. It leads to a deep PMD description from the point of view of polarization states, limit values, compensation methods, and methods of measurement. The practical part of this thesis deals with a draft of PMD measurement via Fixed Analyzer method. For the purposes of this measurement, we used the optical spectral analyzer MS9740A. In order to compare measured values, the proposed idea then proceeds to the reference measurement by using a modular platform EXFO FTB--200 in combination with CD/PMD module EXFO FTB-5700. Results of measurements have been evaluated for the limit values defined by the standard. In the last chapter of this thesis, the reference measurements are compared to the Fixed Analyzer method. All the advantages and disadvantages of individual measurement methods are identified at the end of this chapter too.
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Structures in optical fiber
Polreich, Štěpán ; Čučka, Milan (referee) ; Urban, František (advisor)
This thesis describes the basic concepts, principles and basic characteristics od optical fibers. There are some particular types of structures of optical fibers and their use in practice. The work is also presented technology of these structures. For each of the structures is also described in which field are used, if is area of sensor technology or telecommunication technology. Considerable part is dedicated to special structures that are used especially in sensor technology thanks to its high sensitivity. The thesis describes the design of structures which have been machined by using a femtosecond laser and then states in which area thus treated fibers are used.
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Manufacturing of Relief Diffractive Structures for Optical Elements Using Electron Beam Lithograph
Daněk, Lukáš ; Urban, František (referee) ; Klapetek,, Petr (referee) ; Kolařík, Vladimír (advisor)
This thesis describes several techniques for the optimization of the manufacturing of relief diffractive structures used as optical elements by Electron beam lithograph BS600 in the Electron beam laboratory of the Institute of Scientific Instruments of the Academy of Sciences of the Czech Republic. The Electron beam lithograph BS600 was originally developed and constructed in the Institute of Scientific Instruments of the Academy of Sciences of the Czech Republic for Tesla in 1983, but is still developing, which was published. The Electron been lithograph BS600 is specific in these days because of its accelerating potential and is unique in the world because of the possibility to shape the beam. The optimization of manufacturing of relief diffractive structures, used as optical elements, was mostly reached by analysis, bringing optimal solution for the required effect. Moreover, an algorithm was developed for driving the electron beam position, shape, size and the time of each elementary exposition. The analysis showed that is convenient to use mathematical description of separate lines of diffractive structures. A separate subject was carried out for the calibration of the exposition field of the Electron beam lithograph BS600.
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Bragg gratings in optical fibers
Urban, František ; Křepelka, Václav (referee) ; Filka, Miloslav (advisor)
Thesis focuses on the principles and properties of the tilted Bragg fiber gratings. Two models of the principal cladding mode behaviour are proposed and ther respective results compared with experimental data. The experimental setup for the preparation of the tilted gratings is described. The thesis shows the evaluation of the gratings parameters for the set of prepared gratings. Application of the tilted gratings in the sensors is discussed
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Modelling and Optimization of Complex Fiber Diffractive Structures
Helán, Radek ; Lazar,, Josef (referee) ; Tománek, Pavel (referee) ; Urban, František (advisor)
The thesis discusses the fiber Bragg gratings simulations, analysis and design. In the present time, there are several methods to simulate fiber gratings response based on the stated parameters that define their dimensions and material features. However, this work deals with a different issue, that is the synthesis of the input parameters for demanded spectral responses. The main aim of the work is to achieve a synthesis method that would help to discover parameters describing advanced grating structure, based on the required spectral reflectivity. The basic demand for the parameter synthesis is an achievement of the real values in terms of the consequent production of the suggested structure. The described synthesis method considers advanced fiber grating structure as a structure of several uniform grating sections. The input parameters are estimated in steps, using the well-known direct methods in order to obtain grating responses and feedback to establish the parameters changes. The principle methods involve establishment of initial input parameter values and necessary subsequent algorithm leading to optimize the required spectral response. The initial values are calculated by a simplified model based on the coupled theory equations that are handled for the periodic disturbances in cylindrical waveguide. The following optimization uses the multiple thin film stack and transfer matrix methods. The properties of grating structure spectral reflectivity are step by step calculated while using these direct methods. Input parameters are established in the next several steps. Establishment of input parameters is done subsequently, based on the demanded and calculated output spectral reflectivity properties. Optimizing process is limited by possibilities of the grating manufacture technology. It is possible to assemble arbitrary fiber grating structure taking in term the demanded spectral response. Nevertheless, the calculated input parameters are real for the following manufacture. This method could be used to design optical band stop filter, high-pass and low-pass filters or filters for special applications.
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Apodized fiber Bragg grating analysis
Mišurec, Jan ; Holík, Milan (referee) ; Urban, František (advisor)
This work deals with the behavior of the apodized fiber Bragg gratings. The used individual apodized Bragg fiber gratings and mathematical functions for each apodized profiles are described. The work shows the selected apodization waveforms profiles and their step function approximations needed for further simulations.
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Polarization sensitivity of the fibre optics grating sensors
Babieska, Lukáš ; Šifta, Radim (referee) ; Urban, František (advisor)
This diploma thesis deals with the effect of full-length fixation of optical fiber gratings on their polarization dependence. In addition, the effect of primary protection and parameters of optical fiber gratings on their intrinsic polarization dependence was also investigated. The theoretical part of the thesis briefly describes the historical development of optical fiber gratings, the types of optical fiber gratings used and also describes in detail the principles of polarization dependence of optical fiber gratings and the mechanisms of polarization dependence of optical fiber gratings. In the practical part of the thesis, suitable measurement methods for measuring the polarization dependence of optical fiber gratings are proposed. Furthermore, these methods are optimized and used for subsequent measurements of the effect of fixation on the polarization dependence of optical fiber gratings. Many different methods of fixation of the optical fiber gratings were then used to measure the effect of fixation, and the degree of polarization dependence of the optical fiber gratings was evaluated for each of the different fixation methods. The practical part of the thesis is concluded with a detailed summary of the results obtained.
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Processing of signals from fiber optic sensors
Sikora, Vojtěch ; Urban, František (referee) ; Čučka, Milan (advisor)
First two chapters of this paper deals with the division of optical fiber sensors, digital signal processing and includes price comparison of four experimental sensors. In chapter three analysis, description and evaluation of measurment has been demonstrated on Mach - Zehnder interferometer. Last chapter is about application for signal analysis from vibration sensors. Description contains snippets from source code and graphical user interface. This paper includes three fields - fiber optics, digital signal processing and creation of application - and thanks to them it provides solid basis for study of optic fiber sensors.
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