A novel sensor using a polymer coated long-period grating (LPG) has been proposed for monitoring levels of organic contaminants in air or water systems. The sensor operates by detecting refractive index changes in the polymer coating as analytes partition in. Polymer coatings used must be able to reversibly and reproducibly absorb contaminants of interest from the sample and have a refractive index just below that of the fiber cladding. The synthesis and characterization of several chemically selective polysiloxanes is described. Pre-polymer materials are made through the catalyzed condensation of silane monomers. Different functional groups are incorporated either through polymerizing functionalized monomers, or by post-functionalizing the polymer through a platinum-catalyzed hydrosilylation reaction. The pre-polymer materials are crosslinked into elastomeric films using titanium(IV) tetraisopropoxide. The polymer refractive index is controlled through altering the ratios of functional groups within the polymer or changing the loading levels of titanium. Four polymers were made, having different functional groups and optimized refractive indices for use on the proposed sensor. The partition coefficients for the polymers with a variety of solvents are calculated and compared. Each polymer was found to have a slightly different chemical selectivity pattern, demonstrating that a set of polymers could be used to generate a sensor array. Partition coefficient data was calculated from the gas phase by considering the change in polymer refractive index as the solvents partitioned into the polymer. The Lorentz-Lorenz equation was used to model the relationship between the change in refractive index and the solvent concentration within the polymer. Finally, polymers were applied to LPGs and used to successfully detect various solvents from the gas phase. This was accomplished by monitoring the entire LPG spectrum, and also by considering loss at a single wavelength using fiber-loop ring-down spectroscopy. / Thesis (Ph.D, Chemistry) -- Queen's University, 2008-09-26 15:28:35.603

Distributed sensing is highly desirable in a wide range of civil, industrial and military applications. The current technologies for distributed sensing are mainly based on the detection of optical signals resulted from different elastic or non-elastic light-matter interactions including Rayleigh, Raman and Brillouin scattering. However, they can measure temperature or strain only to date. Therefore, there is a need for technologies that can further expand measurement parameters even to chemical and biological stimuli to fulfill different application needs. This dissertation presents a fully-distributed fiber-optic sensing technique based on a traveling long-period grating (T-LPG) in a single-mode fiber. The T-LPG is generated by pulsed acoustic waves that propagate along the fiber. When there are changes in the fiber surrounding medium or in the fiber surface coating, induced by various physical, chemical or biological stimuli, the optical transmission spectrum of the T-LPG may shift. Therefore, by measuring the T-LPG resonance wavelength at different locations along the fiber, distributed measurement can be realized for a number of parameters beyond temperature and strain. Based on this platform, fully-distributed temperature measurement in a 2.5m fiber was demonstrated. Then by coating the fiber with functional coatings, fully-distributed biological and chemical sensing was also demonstrated. In the biological sensing experiment, immunoglobulin G (IgG) was immobilized onto the fiber surface, and the experimental results show that only specific antigen-antibody binding can introduce a measurable shift in the transmission optical spectrum of the T-LPG when it passes through the pretreated fiber segment. In the hydrogen sensing experiment, the fiber was coated with a platinum (Pt) catalyst layer, which is heated by the thermal energy released from Pt-assisted combustion of H2 and O2, and the resulted temperature change gives rise to a measurable T-LPG wavelength shift when the T-LPG passes through. Hydrogen concentration from 1% to 3.8% was detected in the experiment. This technique may also permit measurement of other quantities by changing the functional coating on the fiber; therefore it is expected to be capable of other fully-distributed sensing applications. / Ph. D.

Thesis (Ph. D.)--Miami University, Dept. of Chemistry and Biochemistry, 2006. / Title from first page of PDF document. Includes bibliographical references.

Femtosecond laser direct writing in transparent materials such as glass and optical fibers has been used as a versatile tool in order to fabricate various 3-D photonic structures such as active and passive waveguides, couplers, gratings and diffractive optical elements (DOEs). This capability of patterning and refractive index modification in the bulk of transparent materials depends on the nonlinear absorption phenomenon. This practical technique has the potential to be used for cost effective and simplified manufacturing in various applications. This thesis examines three advanced manufacturing techniques that use ultrashort pulse filamentary propagation induced by nonlinear absorption in the transparent materials. First, a new gradient index lens fabrication method using femtosecond laser direct writing is introduced. Light that passes through the lens with refractive index change resulting from localized energy deposition is focused using a beam profiler. Second, wide welding area of glass samples are used to fabricate microfluidic devices with long channels by adopting customized fixture. The fixture making artificial pressure helps the two glass samples have wide optical contact area and the highly intensive pulse filamentation strongly joins glass slides. As an example of a more specific application, microfluidic samples with long grooves sealed by femtosecond laser welding were successfully fabricated as part of this project. Finally, a screw-shaped, long period grating sensor was fabricated by rotating the optical fiber. This technique enables the fiber core to have asymmetric refractive index change, resulting in higher sensitivity compared to conventional long period grating sensors. Also, a new long-period grating sensor with reverse bending effect has been demonstrated by producing complex pitches of refractive index change. / Graduate

No description available.

This dissertation presents a fibre-optic sensing approach to provide continuous measurements of CO2 concentration at discrete points under typical conditions of geological CO2 storage. Carbon capture and storage is considered to have potential for a large-scale reduction in CO2 emissions in a relatively short period of time while other solutions to replace fossil fuels are being investigated. One significant drawback of carbon capture and storage is the possibility of long-term CO2 leakage. Therefore, the development of reliable technology for monitoring, verification, and accounting of geological CO2 storage is critical to fulfill safety regulations and achieve public acceptance. The major limitations of current technology include relatively low resolutions, high costs, and the lack of continuous monitoring for long periods of time. To address these limitations, two types of fibre-optic sensors are investigated, namely long period gratings and Mach-Zehnder interferometers. The sensing principle for CO2 detection is based on the sensitivity of these sensors to the refractive index of the medium that surrounds the fibre. Fibre-optic sensors are attractive for downhole applications due to the possibility of fabricating inexpensive high resolution devices that are able to operate in harsh environments over long periods of time. This dissertation focuses on increasing the refractive index sensitivity of long period gratings and Mach-Zehnder interferometers by applying coatings that have a high refractive index. The dip-coating method is used to coat long period gratings with polystyrene, and the sensitivity at low refractive indices is increased by tuning coating thickness. The results show that long period gratings coated with polystyrene are able to detect CO2 in gaseous and aqueous media. This work reports the first measurement of CO2 dissolution in water at high pressure with a fibre-optic sensor. Additionally, atomic layer deposition is investigated to coat long period gratings and Mach-Zehnder interferometers with hafnium oxide. The study of this coating technique aims to address the main limitation of the dip-coating method: the challenge to achieve precise control over coating thickness. The results show that atomic layer deposition is suitable to maximize the sensitivity of long period gratings and Mach-Zehnder interferometers at a target refractive index. / Graduate / 0548 / 0752 / 0799 / luismelo@uvic.ca

Besides attenuation, dispersion is the major limiting factor in high data rate fiber optical transmission systems. Dispersion compensation techniques have to be deployed in order to increase the data bandwidth or the reach of fiber optical links. Typically fixed value dispersion compensators are used. However at channel bit rates of 40 GBit/s and beyond adjustable residual dispersion compensator modules (DCM) are needed to guarantee an error free transmission under changing environmental conditions. In this thesis dispersion techniques were investigated which exploit the special propagation properties of higher order modes in custom-designed optical fibers. After a short introduction of state-of-the-art dispersion techniques and their parameters (chapter 2) the modeling and calculation of propagation properties of a particular mode in an optical fiber with an arbitrary, rotation-symmetric refractive index profile is shown (chapter 3). A converter from the fundamental mode and back is needed in order to exploit the propagation properties of a higher order mode (HOM). In this work long-period gratings (LPG) were considered as mode converters (chapter 4) as they can excite selective and nearly lossless a higher order mode. The modeling und calculation of these gratings, based on the fiber calculation of chapter 3, is presented in the first part of chapter 4. Afterwards the manufacturing methods developed during this work are introduced. The spectral properties of realized long-period gratings are discussed and the influence of such factors as strain and temperature on tuning the mode conversion is shown. A dispersion compensator type utilizing only the waveguide dispersion of a certain mode in a custom few mode fiber (FMF) is the subject of chapter 5. The working principle, the fiber design process and first measurements of a realized HOM-DCM with almost completely coupling FMF-LPG are presented. Subsequently the principle of a novel dispersion compensator with an arbitrary dispersion function for a higher or the fundamental mode is explained. In chapter 6 another type of dispersion compensator is investigated consisting of equally distributed long-period gratings along an optical fiber. The fiber pieces between the gratings create a certain time delay between the fundamental mode and the considered higher order mode. It is shown in simulations and in an experiment, that by tuning the mode conversion of each grating and the optical phase relation between the two signal paths in each fiber piece this finite impulse filter structure is so adjusted to function as a tunable residual dispersion compensator.

There is currently a great interest in the field of porous organosilica materials because of the high surface areas (> 1000 m²/g) and narrow pore size distributions which are beneficial for applications such as chromatography, chiral catalysis, sensing or selective adsorption. Periodic mesoporous organosilicas (PMOs) represent an interesting class of hybrid silica materials because of the wide variety of bridging organic groups which can be incorporated within the precursors [(OR)3Si-R-Si(OR)3] giving rise to materials with exceptional properties. We have synthesized and characterized various aromatic PMOs composed of supporting structural monomers (phenylene- or biphenylenebridged) and functional stilbene monomers (cis and trans) (1, 2). The effect of the different synthetic procedures and varying amounts of functional stilbene monomer on the properties of the materials was examined. The functional transstilbene component was determined to be well distributed in a phenylene-bridged PMO using P123 as a pore template from TEM techniques with Os staining. The trans-stilbene linkers were completely transformed to aryl aldehydes through ozonolysis with dimethylsulfide workup. Further transformation of the carbonyl functionality to an aryl imine showed a moderate level of success. Enantiomeric forms of a novel, chiral PMO precursor (CM) were synthesized and incorporated into biphenylene-bridged PMOs. Under basic pH conditions templated with C18TMACl, although very low levels of CM are incorporated, enantiomeric forms of chiral, porous materials are obtained as was verified by distinct mirror-image circular dichroism spectra. Powder XRD patterns suggest that a tightly packed asymmetric biphenylene arrangement may be necessary for the optical activity. Preliminary results using these materials as a chiral chromatographic phase are promising. Finally, a thin film morphology of an ethane-bridged PMO incorporating a thiol ligand, (3-mercaptopropyl)trimethoxysilane, was prepared on a fibre optic cable and used as a component in a heavy-metal sensing application. / Thesis (Ph.D, Chemistry) -- Queen's University, 2011-03-11 17:24:48.997

Besides attenuation, dispersion is the major limiting factor in high data rate fiber optical transmission systems. Dispersion compensation techniques have to be deployed in order to increase the data bandwidth or the reach of fiber optical links. Typically fixed value dispersion compensators are used. However at channel bit rates of 40 GBit/s and beyond adjustable residual dispersion compensator modules (DCM) are needed to guarantee an error free transmission under changing environmental conditions. In this thesis dispersion techniques were investigated which exploit the special propagation properties of higher order modes in custom-designed optical fibers. After a short introduction of state-of-the-art dispersion techniques and their parameters (chapter 2) the modeling and calculation of propagation properties of a particular mode in an optical fiber with an arbitrary, rotation-symmetric refractive index profile is shown (chapter 3). A converter from the fundamental mode and back is needed in order to exploit the propagation properties of a higher order mode (HOM). In this work long-period gratings (LPG) were considered as mode converters (chapter 4) as they can excite selective and nearly lossless a higher order mode. The modeling und calculation of these gratings, based on the fiber calculation of chapter 3, is presented in the first part of chapter 4. Afterwards the manufacturing methods developed during this work are introduced. The spectral properties of realized long-period gratings are discussed and the influence of such factors as strain and temperature on tuning the mode conversion is shown. A dispersion compensator type utilizing only the waveguide dispersion of a certain mode in a custom few mode fiber (FMF) is the subject of chapter 5. The working principle, the fiber design process and first measurements of a realized HOM-DCM with almost completely coupling FMF-LPG are presented. Subsequently the principle of a novel dispersion compensator with an arbitrary dispersion function for a higher or the fundamental mode is explained. In chapter 6 another type of dispersion compensator is investigated consisting of equally distributed long-period gratings along an optical fiber. The fiber pieces between the gratings create a certain time delay between the fundamental mode and the considered higher order mode. It is shown in simulations and in an experiment, that by tuning the mode conversion of each grating and the optical phase relation between the two signal paths in each fiber piece this finite impulse filter structure is so adjusted to function as a tunable residual dispersion compensator.

Orientador: Cristiano Monteiro de Barros Cordeiro / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-23T00:40:04Z (GMT). No. of bitstreams: 1 Osorio_JonasHenrique_M.pdf: 14712524 bytes, checksum: c56cb1bceeba83a10c67851ebb536f59 (MD5) Previous issue date: 2013 / Resumo: Nesta dissertação apresenta-se o desenvolvimento de sensores baseados em fibras ópticas para os quais se projeta a aplicação como sensores biológicos. A primeira montagem abordada é baseada na utilização de microfibras birrefringentes as quais são obtidas a partir do processo de afinamento de fibras ópticas convencionais lateralmente polidas. Tal configuração provém um sensor de índice de refração de altíssima sensibilidade ¿ (3.0 ± 0.2) x 104 nanometros por unidade de índice de refração ¿ mas de baixa robustez. A fim de se obter um sensor mais robusto, estuda se um sensor baseado em redes de período longo mecanicamente induzidas. Tal sensor é menos sensível que o primeiro ¿ (700 ± 30) nanometros por unidade de índice de refração ¿ mas permite a realização de medidas de monitoramento de pequenas variações de índice de refração ¿ como se mostra numa medida da evaporação de etanol quando dissolvido em água. Como variações de temperatura podem interferir nas medidas baseadas em variações de índices de refração, apresenta-se, também, uma configuração para sensoriamento baseada na associação de fibras birrefringentes, a qual permite o monitoramento de dois parâmetros físicos quaisquer (que são definidos de acordo com a escolha das fibras que compõem a configuração) e de forma independente. Uma medida de sensoriamento de temperatura para ambientes desconectados é apresentada para demonstrar a versatilidade do sensor. Finalmente, apresenta-se o início do desenvolvimento de configurações ópticas construídas a partir de um material biocompatível ¿ a seda ¿, o que amplia as possibilidades de aplicação dos sensores ópticos no sentido do desenvolvimento de biosensores / Abstract: In this dissertation, the development of fiber optic-based sensing platforms which can be projected to act as biological sensors is presented. Firstly, a setup which employs birefringent microfibers obtained from tapering down side-polished standard telecom optical fibers is exposed. This configuration provides a highly sensitive refractive index sensor ¿ (3.0 ± 0.2) x 104 nanometers per refractive index unit ¿ but with poor robustness. In order to obtain a more robust setup, a configuration which employs two in-series mechanically induced long-period gratings was studied. Although this setup presented lower sensitivity than the sensor obtained from birefringent microfibers ¿ (700 ± 30) nanometers per refractive index unit ¿, it allowed the performance of measurements for monitoring small refractive index variations. As temperature fluctuations can influence refractive index measurements, a setup in which two birefringent optical fibers are spliced in an in-series configuration for temperature sensing is also presented. By using this setup, it is also possible to independently sense two different physical parameters (which are defined according to the choice of the birefringent fibers to be used). Finally, it is presented the development of optical configurations by employing a biocompatible material: silk. The use of silk-based configurations is very promising since it broadens the optical biosensors applications possibilities / Mestrado / Física / Mestre em Física