National Repository of Grey Literature 51 records found  previous11 - 20nextend  jump to record: Search took 0.00 seconds. 
Reliability, security and transfer parameters of optical cables
Kučera, Zdeněk ; Křepelka, Václav (referee) ; Filka, Miloslav (advisor)
Communication via fiber optic cable is the latest advancement of the transmission media currently used for data transmission. Despite initial problems, using of this medium in recent years has greatly expanded due to their indisputable advantages. Optical cable is a great combination of reliability and security of data transfer. Its constantly improving transmission parameters contribute to the high speeds in the long-distance transmission of data. In the theoretical part of this work some kinds of optical cables are mentioned, also the most important parameters and the most widely used methods of measurement of these cables. The comparison and evaluation of the measured values of attenuation and the real length of optical paths was done by several types of measuring instruments in the practical part.
Optical transmission applications in industries
Worbis, Vít ; Křepelka, Václav (referee) ; Filka, Miloslav (advisor)
The aim of the semestral work term use of optical transmission in the industry is to find the right equipment for communication in industrial applications, which would lead to better control and management of these applications. My show almost seamless connection between the device, which is controlled by another device such as a computer. The first chapter shows how inside the core optical fiber and reflected beams are then carried around the skylight. The second section lists the differences between the copper and fiber cabling, there is described why metallic line slowly destroyed and replaced him fully optics. In the third chapter, I focused on the optical fiber, what are its characteristics, from which parts are made and what is distributed. In the fourth part shows the optical transmitters for multimode and singlemode optical fibers, which are differences between them, which are produced and with what characteristics, etc. In the fifth chapter is applied to a network of possible involvement in the industrial zone, is designed only as they could theoretically be industrial zone controlled by the machine. In the sixth part of the thesis I have tried to design a laboratory task that consists of those optical converters. It is only a small sample, as used in the industry far more extensive involvement.
Measuring unit for analysis of fibre grid properties
Urban, František ; Křepelka, Václav (referee) ; Filka, Miloslav (advisor)
Thesis focuses on measurement of the properties of the Bragg faber gratings.The method of measurement is based on the spectral scanning by use of the thermal tuning of the laser diode. The optical fiber set for greating evaluation is designed. The thesis contains the design of the electronic control board for laser diodes and photodetectors.
Spectral characteristics measurement of single fibre optical transmission
Balon, Radek ; Křepelka, Václav (referee) ; Filka, Miloslav (advisor)
The main object of the bachelor´s thesis is show familiarize with optical networks and measuring when the fibres are connected to operating network. The whole thesis was separated into several parts. The first part was deals with optic fiber and properties, kinds of optic fibers, methods of propagation light inside fiber and important parameters, which has undesirable effects, such as optic loss and dispesive influences. Next part was concentrated on transfer technologies, which where used for data transmission in operating networks. We talked about differences between technologies and describe the monitoring system, which was used for measuring parameters in operating network. The last part was focused on own measuring. We was measured the parameters in operating network CESNET2 and influence of the signal after connect optic monitoring probe. Measuring was implemented on optical network of Masaryk University in Brno (ÚVT MU).
The quality of assembly in data transmission
Šalplachta, Milan ; Křepelka, Václav (referee) ; Filka, Miloslav (advisor)
The content of this work is theoretical and practical an analysis of transmission characteristics of structured cabling and related effect of assembling, which directly affects the characteristics of channel. Individual treshold limits of channel parametres, as technological methods of montages are outgoing from corresponding european specifications.
Critical Parameters for Wireless Networks WiFi and WiMAX
Grenar, Milan ; Křepelka, Václav (referee) ; Baroňák, Ivan (referee) ; Filka, Miloslav (advisor)
My thesis will be aimed at problems of wireless networks WiFi and WiMAX. A modelling of network will be put into effect onto which the measurement will be implemented and the impacts of network load on the data transfer Quality of Service (QoS) will be examined with aiming at VoIP. On this network model a power failure will be simulated and the impacts of this failure after restoring the power supply will be monitored. The aim of this thesis is to check the rate of network throughput while preserving a providing service quality and to suggest an economica1ly acceptable solution of the problems relating to feeding tension outage of the access point (AP) for a practical usage in these networks.
Quality of Services in Optical Access Networks
Šifta, Radim ; Křepelka, Václav (referee) ; Vlček, Čestmír (referee) ; Filka, Miloslav (advisor)
The thesis focuses on the optical access networks and deals with the issue of transmission parameters of the physical layer, their negative impact on the quality of the services parameters and the possibilities of reducing their effect using the polarization multiplexing. The first and second chapter describe the theoretical background necessary for understanding the subsequent parts. The third chapter contains the practical part of the thesis. At first the optical routes in the Czech Republic in terms of polarization mode dispersion, which is together with insertion loss the main limiting parameter of high-speed optical networks, are evaluated. In the following part the measuring of the temperature changes effects on the polarization mode dispersion of the passive components and the effect of temperature changes to the polarization multiplexed signal are evaluated. To double the bandwidth and reduce the influence of polarization mode dispersion on the quality of services, the two simulation models of optical access networks using polarization multiplexing were carried out. These theoretical outputs were verified by the practical measurements in the laboratory and subsequently on the real optical route. Finally, a draft of the broadband optical access network based on wavelength and polarization multiplexing was designed based on obtained knowledge.
Quality of Service in Converged Systems with Elements Controlled by Neural Network
Polívka, Michal ; Sýkora, Jiří (referee) ; Křepelka, Václav (referee) ; Škorpil, Vladislav (advisor)
The Quality of Service (QoS) is in converged systems an important parameter. The dissertation thesis deals with research of QoS implementation into a newly developed network element. There was designed and implemented new protocol, based on the IP. The dissertation thesis deals with proposal of a new network element – the switch controlled by a neural network. During the research have been measured switches cross a performance classes. On the base of the measurement was designed the new four-port switch with switch fabric build on crossbar switch with an external control. The switch was designed with maximum QoS support. The switch fabric is controlled by the feedforward backpropagation neural network. The designed switch was modeled in the MATLAB and Simulink. The simulations prove that developed solution is functional.
Parameters of FTTx Networks
Münster, Petr ; Křepelka, Václav (referee) ; Vlček, Čestmír (referee) ; Filka, Miloslav (advisor)
This thesis examines parameters of FTTx networks and possibilities for increases in limit values of some selected parameters. The first and second chapters describe the necessary theory for understanding the outcomes presented in the rest part of the work. In the practical part of this thesis, analysis of the condition of the optical fibers in the Czech Republic is provided. Based on the results, the impact of the polarization mode dispersion on optical access networks was assessed. The next part of this thesis is focused on the active optical networks design, depending on the cost of implementation and operating costs. The main limiting parameters of the current passive optical networks are bandwidth and insertion loss of the optical distribution network. To increase the bandwidth a system based on optical time-division multiplexing with a bandwidth of 1.28 Tbit/s has been designed and created. By using polarization division multiplexing technique the system is also more tolerant to dispersions. In the last part of this thesis, a remote amplification system was verified by measurement and simulation. Based on the obtained results, a NG-PON2 network with a functional remote amplification system with a gain of more than 10 dB has been designed in the OptiSystem software.
Localization in Wireless Energy-Constrained Networks
Morávek, Patrik ; Vozňák, Miroslav (referee) ; Křepelka, Václav (referee) ; Komosný, Dan (advisor)
Tato disertační práce se věnuje lokalizaci v bezdrátových sítích se zaměřením na odhad vzdálenosti. Lokalizace je v bezdrátových sítích s mobilními ale i statickými uzly důležitým procesem, neboť znalost pozice uzlů může být během provozu sítě dále s výhodou využita. V práci je prezentována nová metoda odhadu vzdálenosti na základě měření síly přijatého signálu. Navržená metoda je postavena tak, aby s co nejnižšími energetickými náklady dosáhla požadovaného stupně přesnosti i ve značně odlišných rádiových podmínkách. Před návrhem vlastní metody byla provedena experimentální analýza spotřeby anergie a šíření signálu s jeho využitím pro lokalizační účely. Na základě provedené analýzy byla navržena nová metoda (Adaptabilní energeticky nenáročná metoda odhadu vzdálenosti), která byla následně ověřena v simulátoru a experimentální síti za reálných podmínek.

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