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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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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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Seismic activity measurement using fiber optic sensors
Vaněk, Stanislav ; Horváth, Tomáš (referee) ; Vojtěch, Josef (advisor)
The aim of master's thesis is to get familiarized with the problems of measurement and analysis of seismic waves. Theoretical part deals with the description of seismic waves, especially their types, sources and properties. Attention was afterwards focused on the measurement systems of these waves, emphasis was placed on their principles and advantages. The practical part discusses methods of noise reduction and highlighting of significant events in measured data. At the end, individual methods are implemented into user-friendly graphical interface.
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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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Longitudinal Photonic Structures in Optical Fibres
Urban, František ; Róka,, Rastislav (referee) ; Slavíček, Karel (referee) ; Smékal, Zdeněk (advisor)
The focus of the thesis is to analyse the specific ways and the means of preparation of the longitudinal quasi-periodical optical structures of the Bragg grating type made in the fibre waveguides with a scope of forming the fibre diffractive elements for sensorics. Apodized Bragg gratings and their design and preparation based on the overlying of two or more nonidentical uniform structures became the target of the work. The first part presents the Bragg grating theory and the outline of the grating types and features. Further the thesis discusses the important aspects of grating applications in sensors. The ways of sensorial grating optimization and grating evaluation optimization are shown. Chapter 4. shows the impact and properties of the grating apodization. The next part of the thesis spreads and generalises the usage of the Moaré method of apodized gratings preparation. The principles of the generalized method are introduced and its math description based on the multiple nonequal subgratings overlays formulated. The math formulation respects the specifics of the gratings writing by the side exposition of the fibre with the interference pattern of the UV radiation passing through the phase mask, where all the subgratings use the common mask and the fibre stretches and shifts are applied. These principles are applied in optimised designs of nine application specific grating structures using two and three subgratings. Chapter 6. presents the necessary steps for the exposition system to adopt the needs of the generalised Moaré method and shows the results of the experimental works in the preparation of the designed apodized two and three subgrating based structures. The optimized grating structures with high side lobe suppression, structures with sharp central reflectance drop and the structures with flat reflectance maximum are presented.
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The Point-by-Point fiber diffraction structures
Valášek, Martin ; Čučka, Milan (referee) ; Urban, František (advisor)
The diploma thesis described the basic principles and characters of the long period fiber gratings (LPFGs). Our concern was to describe basic mathematical description of these gratings needed to their modelation and simulation. Consequently some exact models leading to changes in the shape of the spectrum LPFGs were suggested, these methods were the chirping, apodization and changes in the average refractive index navg. In the Matlab environment, programes for counting the important parametres LPFGs were created and meanwhile each model leading to the change in the shape of the spectrum was simulated.
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Design of the method to increasing of accuracy of the tunable optical filter optical spectra measurement
Jelínek, Michal ; Holík, Milan (referee) ; Mikel, Břetislav (advisor)
The thesis deals with the method for the improvement of the measurement accuracy in the optical frequency spectra measurements based on tunable optical filters. The thesis starts with the selection of the proper optical filter that is suitable for accurate light spectrum measurement. The selected filter was then used for the design and realization of the measurement system for the inspection of the fibre Bragg gratings. The system incorporates a reference block for the compensation of environmental influences, an interferometric verification subsystem and a PC - based control software implemented in LabView. The preliminary experimental verification of the measurement principle and the measurement system functionality were carried out on a testing rig with a specially prepared concrete console in the UJV Řež. Advanced tests were conducted on nuclear power plant’s containment shape deformation measurement in Temelin.
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Longitudinal index structures in optical fibers
Polreich, Štěpán ; Čučka, Milan (referee) ; Urban, František (advisor)
This thesis describes basic concepts, principles and properties of optical fibers. Considerable part is devoted to fiber gratings that are created by a change in the refractive index in the optical fiber core. In this work is described description, principle, method od production and distribution of gratings on Bragg gratings, gratings with long period and chirped gratings. In this thesis are also presented different types of lasers and their advantages over other lasers. A large part deals with the description of the femtosecond laser, with which the structures will be later made into the material. In addition, the laser modes are differentiated, this is a mode of micro-machining and modification or a change in refractive index of the material. The last part deals with change the refractive index in planar technology, the creation of a groove for fastening the fiber and attempts to write the gratings into the optical fiber. Created fiber sensor are tested for temperature and tensile changes. Finally, the practical use of sensors made by femtosecond laser and the advantages over UV laser and phase mask techniques are presented.
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