Analysis of the applicability of singlemode optical fibers for measurement of deformation with distributed systems BOTDR

Distributed optical fiber sensors allow monitoring physical effects across the whole cable. The paper presents results obtained from the performed tests and shows that single mode fibers can provide analyses of the deformation changes, when distributed optical systems BOTDR used. We used standard optical fiber G.652.D with primary and secondary protected layers and specialized cable SMC-V4 designed for this purpose. The aim was to compare the deformation sensitivity and determine which fiber types are the best to use. We deformed the fiber in the longitudinal and transverse directions and mechanically stressed in orthogonal directions to find how to localize optical fibers. They could be deployed in real use. For achieving optimal results of mechanical changes and acting forces, sensor fibers have to be located carefully

Non-destructive fiber-optic sensor system for the measurement of speed in road traffic

Fiber-optic sensors offer an attractive option to existing sensors for the measurement of the vehicle speed in road traffic. This article describes the measuring scheme of two interferometric sensor units including input-output components for the measurement of the vehicle speed. The interferometric sensors operate on a principle of Mach-Zehnder interferometer. The sensors are constructed to detect a vibration caused by vehicles moving on roads. The sensor system processes the vibrational response, and the vehicle speed is calculated in a time domain. DFB laser was used with a wavelength of 1550 nm and output power of 1--5~mW. The solution provides very high sensitivity. The performance of the proposed system was verified by a series of experimental measurements of the speed. The vehicle speed was monitored by GPS. The highest relative difference of the evaluated speed against GPS data was 7.7 %, the smallest was 1.36 %. When recalculated on kph, the absolute error ranged in the tolerance ± 3 kph, which denotes segmental measuring systems in CZE

Encapsulation of FBG sensor into the PDMS and its effect on spectral and temperature characteristics

Fiber Bragg Grating (FBG) is the most distributed type of fiber-optic sensors. FBGs are primarily sensitive to the effects of temperature and deformation. By employing different transformation techniques, it is possible to use FBG to monitor any physical quantity. To use them as parts of sensor applications, it is essential to encapsulate FBGs to achieve their maximum protection against external effects and damage. Another reason to encapsulate is increasing of sensitivity to the measured quantity. Polydimethylsiloxane (PDMS) encapsulation appears to be an interesting alternative due to convenient temperature and flexibility of the elastomer. This article describes an experimental proposal of FBG PDMS encapsulation process, also providing an analysis of the FBG spectral characteristics and temperature sensitivity, both influenced by high temperature and the process of polydimethylsiloxane curing itself. As for the PDMS type, Sylgard 184 was employed. Encapsulation consisted of several steps: allocation of FBG to PDMS in its liquid state, curing PDMS at the temperature of 80°C ± 5 %, and a 50-minute relaxation necessary to stabilize a Bragg wavelength. A broadband light source and an optical spectrum analyzer were both used to monitor the parameters during the processes of curing and relaxation. Presented results imply that such a method of encapsulation does not have any influence on the structure or functionality of the FBG. At the same time, a fourfold increase of temperature sensitivity was monitored when compared to a bare FBG

Perimeter system based on a combination of a Mach-Zehnder interferometer and the Bragg gratings

Fiber optic interferometers and Bragg gratings belong to the group of very precise and sensitive devicesthat allow measuring very small deformation, temperature or vibration changes. The described methodology presentsthe useof a Mach-Zehnder interferometer and Bragg gratings together as a sensor system for detecting and monitoring movement within thedefined perimeter of 2.5×1m. Analyses of the dynamic changes in interferometric patterns were a basis for this method. Also the signal maximum amplitude was measured and compared with the noise background. Perimeter disruptions can be detected by Bragg gratings due to its large deformation sensitivity in transversal or perpendicular directions. The result is then evaluated in the spectral domain. In terms of detected persons it showed very good results. The combination of these sensors was chosen for monitoring both the static and dynamic phenomena. Author's aim is to take advantage of both devices' positive properties. Thus, the system has the abilityto identify people due to frequency analysis in case of interferometers as well as dynamic weighting thanks to Bragg gratings

The Error Rate Measurement in PON Network

Import 26/06/2013Celá práce se zabývá problematikou pasivních optických sítí, konkrétně technologií GEPON. Hlavním cílem práce je proměření chybovosti pomocí testu RFC 2544 a EtherSAM na vytvořených topologiích. Teoretická část se zabývá popisem technologie GEPON, dále pak teoretickým rozborem metod měření útlumu v optických sítích a jejich vlivem na danou síť. Praktická část obsahuje popis daných testů, jejich způsoby testování a prezentaci výsledků. Dále pak v praktické části jsou popsány vytvořené topologie, nalezen jejich maximální možný dosah fungování a taktéž následné vyhodnocení všech naměřených výsledků, spolu se zhodnocením dané topologie z pohledu porovnání výsledků obou testovaných metod.The entire work is focused on passive optical networks, specifically the GEPON technology. The main aim of this work is to measure the error rate test RFC 2544 and EtherSAM on created topologies. The theoretical part deals with the description of the GEPON technology, theoretical analysis of attenuation measurement methods in optical networks and their impact on the network. The practical part includes a description of the tests, their ways of testing and presentation of the results. The practical part describes the created topology, found their maximum range of operation and also the subsequent evaluation of all the results obtained, together with the appreciation of the topology as seen from the comparison of the results of both test methods.440 - Katedra telekomunikační technikyvýborn

Aplikace izotermální a izoperibolické kalorimetrie k posouzení vlivu zinku na hydrataci cementu smíseného se struskou.

This work deals with the influence of zinc on cement hydration. The amount of zinc in cement has increased over recent years. This is mainly due to the utilization of solid waste and tires, which are widely used as a fuel in a rotary kiln. Zinc can also be introduced to cement through such secondary raw materials as slag, due to increased recycling of galvanized materials. The aim of this work was to determine the effect of zinc on the hydration of Portland cement, blended with ground blast furnace slag (GBFS). This effect was studied by isothermal and isoperibolic calorimetry. Both calorimetry methods are suitable for measurements during the first days of hydration. Isoperibolic calorimetry monitors the hydration process in real-life conditions, while isothermal calorimetry does so at a defined chosen temperature. Zinc was added to the cement in the form of two soluble salts, namely Zn(NO3)(2), ZnCl2, and a poorly soluble compound, ZnO. The concentration of added zinc was chosen to be 0.05, 0.1, 0.5, and 1mass percent. The amount of GBFS replacement was 15% of cement dosage. The newly formed hydration products were identified by X-ray diffraction method (XRD).Práce se zabývá sledováním vlivu zinku na průběh hydratace a změnu fázového složení cementu smíseného se struskou. Pro kvantifikaci vlivu zinku a příslušných aniontů byly délky indukčních period proloženy expenenciální křivkou

Použití Izotermické a Izoperibolické kaloriemtrie pro studium vlivu zinku na hydrataci cementů smísených s popílkem

Increasing utilization of secondary raw materials and alternative fuels results in increasing contents of metals in cements. Zinc is one of these elements. It comes to cement with secondary raw materials such as slag or fly ash or by the utilization of used tires as an alternative fuel. Zinc ions significantly prolong the hydration process in cement. This work deals with the influence of zinc ions in the form of very poorly soluble ZnO salt and easily soluble ZnCl2 and Zn(NO3)(2) on the hydration of cement blended with fly ash. Zinc was dosed in the range of 0.05%, 0.1%, 0.5% and 1% of cement weight. The effect of zinc on hydration was monitored by isothermal and isoperibolic calorimetry. A 15% addition of fly ash to cement mainly causes further retardation of hydration reactions due to the reactions of fly ash particles with Ca2+ ions from cement. The strongest effect on the hydration retardation from all investigated compounds showed in ZnO as it dissolves very slowly. On the contrary, for the dosage of 1% of zinc in the form of ZnCl2 significant acceleration of hydration occurred. In this work, a synergistic effect on the prolongation of hydration with a combination of cement, zinc and fly ash was demonstrated. The lengths of induction periods were assessed from detected calorimetric curves and from these lengths the curves were gained by fitting with the exponential function. Final products were next analyzed using X-ray diffraction.Zvyšující se míra využití druhotných surovin a alternativních paliv vede ke zvýšení obsahu kovů v cementech. Zinek je jedním z těchto prvků. Zinek následně přechází do cementu a druhotných surovinami, jako je struska nebo popílek. Zinek také přechází díky využití použitých pneumatik jako alternativního paliva. Ionty zinku významně prodlužují proces hydratace v cementu. Tato práce se zabývá vlivem iontů zinku ve formě velmi špatně rozpustné soli ZnO a snadno rozpustných ZnCl2 a Zn (NO3)2 na hydrataci cementu smíchaného s popílkem. Zinek byl dávkován v rozmezí 0,05%, 0,1%, 0,5% a 1% hmotnosti cementu. Vliv zinku na hydrataci byl sledován izotermickou a izoperibolickou kalorimetrií. 15% přidání popílku do cementu způsobí hlavně další zpomalení hydratačních reakcí v důsledku reakcí částic popílku s ionty Ca2+ z cementu. Nejsilnější účinek na zpomalení hydratace ze všech zkoumaných sloučenin se ukázal v ZnO, protože se rozpouští velmi pomalu. Naopak u dávky 1% zinku ve formě ZnCl2 došlo k významnému zrychlení hydratace. V této práci byl prokázán synergický účinek na prodloužení hydratace kombinací cementu, zinku a popílku. Délky indukčních period byly hodnoceny z detekovaných kalorimetrických křivek a z těchto délek byly křivky získány příslušné exponenciální funkei. Konečné produkty byly dále analyzovány pomocí rentgenové difrakce