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Transmission parameters of optical access networks
Ježek, Jaroslav ; Kapoun, Vladimír (referee) ; Havelka, Dušan (advisor)
The essence of this thesis is the cognition of theoretical basis for measuring on optical fibres, elements and optical wireway as well. This work describes the methods of measuring and detection of parameters of these networks. The gained knowledge is followed by its application on two laboratory tasks. The first task is focused on usage of method of embedded loss for measuring of attenuation of fibre and followed by usage of the method OTDR for localization of defect. The second task is focused on measuring of attenuation on passive optical element using only the method of embedded losses. The laboratory tasks were described and respective conclusion and findings were drawed from each other.
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Polarization mode dispersion
Turský, Aleš ; Dostál, Otto (referee) ; Filka, Miloslav (advisor)
The work deals with dispersive effects of single mode fibers. We learn about the chromatic dispersion, the main attention is paid to the Polarization Mode Dispersion. We clarify the root cause origin of the Polarization Mode Dispersion describing parameters and its effect on transmitted data. Further on, the works dedicates to measure methods of the Polarization Mode Dispersion which is the interferometric method or the POTDR method. We explain the ways of the PMD removal at contemporary optic routes and options of PMD compensation by using compensators of various types. There is also mentioned the possibility of profiting from the soliton transmission. The last chapter deals with measuring of a real optic route. It includes measured data and its evaluation due to the ITU-T demands.
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The Optical Link Error-Rate Determination
Joch, Antonín ; Kapoun, Vladimír (referee) ; Kyselák, Martin (advisor)
The master thesis discusses physical causes of light polarization and problems brought by nascence of Polarization Mode Dispersion (PMD). These problems occur especially by high speed systems on optical cable traces. The thesis deals with actuation of transmitted signal by influence of Inter Symbol Interference and it also deals with methods for its measuring and compensation. As a results of measurements are in text presented data provided by EXFO Electro-Optical Engineering Inc. Company. Significant part of the thesis focuses on optical link Bit Error Rate (BER) which is connected with Signal to Noise Ratio (SNR) and signal quality (Q-factor). Further on it is possible to find in text about so called eye diagram which is display mode that shows influence of communication channel on shape of the transmitted signal. To this diagram is related another one called constellation diagram which describes modulation mode and makes it possible to map dispersion of signal points around their nominal values. In connection with so called trajectory it makes vector diagram. Practical part includes depiction of these diagrams in MATLAB development environment.
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Preparation of graphene samples for experiments under UHV conditions
Mareček, David ; Mach, Jindřich (referee) ; Čechal, Jan (advisor)
This bachelor thesis deals with electrical conductivity of a graphene sample and preparation of a graphene field-effect transistor. In the theoretical part of the thesis, we describe electronic properties of graphene, preparation of graphene by CVD and its transfer to SiO_2. Experimental part of this thesis is focused on the preparation of a graphene field-effect transistor with long distance between Source and Drain electrodes. Thesis deals with a design of a chip expander for contact of graphene in UHV conditions. The last part describes measurement of dependency of graphene layer conductivity on the gate voltage with emphasis on the position of Dirac point during adjustments of the sample in UHV conditions.
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Utilization of Nanofibres in the Traditional Ceramics Body
Sedláček, Daniel ; Stančík,, Hynek (referee) ; Sokolář, Radomír (advisor)
This thesis summarizes the current knowledge about ceramic composites with nanofibers. So far, most research focused on the reinforcement of hi-tech ceramics, such as carbides and nitrides, however, this traditional ceramics left behind. Due to the improving the efficiency of production of nanofibers and thus a drop in prices, companies consider their use even in a cheaper ceramic materials. Reinforcement of traditional ceramic shard could theoretically improve many characteristics, but there are absolute minimum of practical researches.
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Ant food preferences (Formica genus) on the seeds with elaiosomes
ENGLICKÝ, Tomáš
The topic of the presented bachelor thesis is the determination of the ants g. Formica preference for specific seeds with elaiosomes. The ant dispersion of the seeds with elaiosomes is called myrmecochory. The theoretical part of this thesis describes the myrmecochory phenomenon in the context of the seed dispersal. The conclusion of the theoretical part evaluates considerable benefit of myrmecochory for ants and plants despite its disadvantages. The practical part of this thesis describes the experiment held with the intention to determine the preferences of the ants. The seeds with elaiosomes from five experimental plants were presented to the ants from two experimental anthills. Obtained data were processed into tables and graphs and subsequently evaluated. The results show that the ants prefer certain types of seeds. The cause for this preference is discussed.
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Long-term monitoring of the movement and location of individuals yellow-bellied toad (\kur{Bombina variegata})
VOLFOVÁ, Tereza
This thesis contains brief knowledge about homing and migration in amphibians. In practical part this thesis is studied fidelity and movement yellow-bellied toad (Bomnina variegata) in observed lokality. It is maped relative quantity during four seasons. Habitat preferences of yellow-bellied toad are researched depend on chosen paramerts (maximal depth, area, vegetation). This thesis also devote a pattern maps, special technice for marking amphibians. This method was used for marking individuals of yellow-bellied toad in field experiment.
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Dispersal and flight activity of aquatic insects: mechanisms and consequences for community assembly.
VEBROVÁ, Lucie
Water insects represent the considerable part of the freshwater communities. One of the most spectacular ability of those organisms is dispersion among various localities. The understanding of the dispersion mechanisms is of the key importance for unhiding the basic ecological and evolutionary processes such as colonization or maintaining high diversity patches. The aim of this thesis is to summarize findings about the dispersion and its main drivers. The experimental part deals with the influence of environmental factors on the flying activity of the water insects.
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Individual marking of small insects and its usage in describing societies and migration of semiaquatic bugs (Heteroptera: Gerromorpha) in lentic and lotic habitats of Novohradské Mountains.
VOJÍŘOVÁ, Eva
Experiments based on the method of mark-recapture can be used for estimation of the abundance of natural populations, for monitoring dispersion of groups or individual specimens within a population using group or individual marking. Semiaquatic bugs (Heteroptera: Gerromorpha) were marked and recaptured many times in the field during research, individual marking was much less used since marking of small insects is difficult. The aim of this work is to develop a method of individual marking of semiaquatic bugs so that it would meet conditions such as durability, legibility and non affecting health of the marked specimen. Semiaquatic bugs of Aquarius paludum, Gerris lacustris, Limnoporus rufoscutellatus (Gerridae) and Velia caprai (Veliidae) species were selected as experimental organisms. Partial aims of this thesis were to try using this method to describe the abundance of the monitored population and to monitor dispersion of the selected species, both at lotic (V. caprai) and lentic habitats (water striders, family Gerridae). A new method of individual marking of semiaquatic bugs was developed on the basis of modifications of the commonly used methods. After a series of tests and in-field research, this method proved to be suitable as it met the essential conditions for marking insects. The abundance of the monitored population was estimated and dispersion of the selected species (V. caprai) in running water was described by using this method. The partial aims of this thesis were met, too. It was confirmed that individuals of the V. caprai species move between the monitored areas along the water course. This inclination to move is greater than tendency to remain in the place of release. The gained data also show conclusively higher rate of movement of V. caprai specimens in the upstream direction, compared to the downstream. The tendency of V. caprai to travel larger distance upstream than downstream, is significant too. No statistically relevant difference in either direction of the water course (up or down) in the surpassed altitude difference was confirmed. The differences in the monitored phenomena between the sexes and generations were compared as well. The differences, however, were not significant. A movement of the adults of the water cricket Velia caprai thus can be characterized as an upstream migration, common in insects of lotic habtitats. A part of the study taking place in still waters showed, that G. lacustris specimens move on the surface of the pond, but not to a larger degree than they remain in place. On the other hand, A. paludum specimens were proved to move away from the place of release rather than remaining in that place. These also overcome greater distance than G. lacustris specimens.
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