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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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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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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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