[pt] A magnetostricção é a propriedade dos materiais ferromagnéticos de se deformarem pela presença de um campo magnético externo. Trata-se de uma propriedade inerente ao material, que não muda com o tempo. Materiais que apresentam deformações da ordem de 10-3 são conhecidos como materiais de magnetostricção gigante (GMM). Esta dissertação de mestrado estuda a aplicação destes materiais em sensores de deslocamento onde não há contacto entre o elemento cursor (um ímã) e o elemento sensor (GMM). O princípio de funcionamento consiste em aplicar um gradiente de campo magnético ao GMM que está fixo. O gradiente de campo magnético é gerado por um ímã preso ao componente ou estrutura na qual se quer medir o deslocamento. As variações no campo magnético no material GMM originados pelo deslocamento do ímã (estrutura), provocam uma deformação no GMM, que é detectada com extensômetros do tipo Strain Gauge ou Redes de Bragg. Neste trabalho apresenta-se a caracterização da deformação de GMM em relação a um campo constante aplicado, e análises do seu comportamento para diferentes geometrias. Efeitos de pressão, polarização com um segundo ímã, e diferentes gradientes de campo magnético são também estudados. É observado um comportamento local para a deformação quando a medida é realizada em diferentes regiões do GMM. Os resultados obtidos permitiram a medição de deslocamentos de alguns micra estando o elemento sensor a até 10 mm de distância do elemento cursor. / [en] Magnetostriction is a property of ferromagnetic materials to deform in the presence of a magnetic field. Magnetostriction is an inherent property of magnetic materials, which is unchangeable with time. Materials exhibiting strains in the order of 10-3 are known as giant magnetostrictive materials (GMM).In this dissertation we study the application of these materials in displacement sensors where there is not contact between the cursor element (magnet) and sensor element (GMM). Its principle of operation consists of applying a magnetic field gradient to a GMM located at a fixed position. The magnetic field gradient is produced by a magnet attached to the component or structure in which the displacement will be measured.The variation on the magnetic field in the GMM position originated from the displacement of the magnet, results in a strain in the GMM that can be detected with a Strain Gauge or Bragg Grating extensometers. In this work is presented the characterization of the strain on GMM cuboids against a constant magnetic field and the analysis of its behavior for different geometries. Effects of pressure, polarization with a second magnet, and different gradients of magnetic field are also studied. It is observed a local behavior for strains when it is measured in different regions of GMM cuboid. The results obtained allow us to measure displacements of about few micra when the sensor is at a distance of 10 mm from the cursor element.

Fibre Bragg gratings (FBGs) are key components for a vast number of applications in optical communication systems, microwave photonics systems, and optical sensors, etc. The main topic of this thesis is fibre Bragg grating fabrication and applications in direct microwave optical filtering, high speed switching and switchable dual-wavelength fibre lasers. First, a brief overview is given about the photosensitivity in optical fibre, basic FBG fabrication techniques, the popular coupled-mode theory for describing fundamental characteristics of FBGs and the Transfer Matrix method for the numerical simulations of complex-structured FBGs. An advanced FBG fabrication system based on the technique of multiple printing in fibre (with a continuous-wave source) has been used to write complex FBGs incorporating phase shifts, apodization and chirp.      A single double-peaked superimposed grating working in reflection can be employed as a direct optical filter for millimetre-wave signals. Bit error rate measurements confirmed that the filter exhibited nearly on-off behaviour in the passband with a 3-dB bandwidth of 2 GHz for a central frequency of 20 GHz, as expected from the optical spectrum reflection. The presented technique can be used in radio-over-fibre systems or simultaneous up-conversion of ultra-wide band signals and filtering. This thesis focused mostly on the research of two 4-cm long Hamming-apodized gratings written in side-hole fibres with internal electrodes. The temperature dependence measurements showed that the birefringence of the component increased with the temperature. Dynamic measurement has shown nanosecond full off-on and on-off switching. During the electrical pulse action, the grating wavelength was blue-shifted for the x-polarization and red-shifted for the y-polarization due to the mechanical stress. Both peaks subsequently experienced a red-shift due to the relaxation of mechanical stress and the increasing core temperature transferred from the metal in many microseconds. All the wavelength shifts of the two polarizations depend quadratically on the electrical pulse voltage and linearly on the pulse duration. Numerical simulations gave accurate description of the experimental results and were useful to understand the physics behind the birefringence switching. Finally, two switchable dual-wavelength erbium-doped fibre lasers based on FBG feedback were proposed. In one method, an overlapping cavity for the two lasing wavelengths and hybrid gain medium in the fibre laser were introduced. Dual-wavelength switching was achieved by controlling the Raman pump power. The other method employed an injection technique and the dual-wavelength switching was controlled by the power of the injection laser. The switching time was measured to be ~50 ms. Detailed characteristics of the dual-wavelength switching in the two fibre lasers were experimentally studied and corresponding principles were physically explained. / QC 20100922

The nuclear industry shows an increasing interest in the fiber optic technology for both data communication and sensing applications in nuclear plants. The optical fibers offer several advantages and the sensors based on this technology do not need any electrical power at the sensing point, they have a quick response and they can be easily multiplexed: in the case of a temperature sensor, several thermocouples can be substituted by a single fiber, resulting in a decrease of the waste material. The fission reactors are a very harsh environment: it is characterized by the highest dose of gamma-rays, of the order of magnitude of GGy, besides a high flux of neutrons and high operating temperature (300°C for the current reactors, known as generation III). This work has been carried out in collaboration with AREVA, a French industrial conglomerate active in the energy domain, with the aim of realizing a temperature sensor resistant to the environment of nuclear reactor of generation IV, in particular a Sodium-cooled Fast Reactor. The currently used technology, the thermocouples, presents a drift of the measurement due to irradiation, that needs a calibration, and a long response time on the order of seconds. In order to remove the drift, to reduce the response time and to increase the precision, a Fiber Bragg Grating temperature sensor was chosen, in regard to all the advantages of the optical fibers. To understand the behavior of such system in a harsh environment, as the nuclear reactor core, we used an experimental approach based on complementary techniques such as radiation-induced attenuation, photoluminescence, electron paramagnetic resonance and Raman spectroscopies

Multimode devices play an increasingly important role in both communication and sensing systems. Mode division multiplexing (MDM) in multimode fiber (MMF) is becoming a promising method to further increase the capacity of optical transmission link with a controllable mode coupler. Similarly, optic sensors based on core-cladding-mode interference can be widely used in measurement of refractive index (RI), temperature and strain. Fiber Bragg gratings (FBGs) in single mode operation have been extensively studied as in-line optical components for both communication and sensing applications. In recent years, research has been extended to FBGs in few-mode operation as mode couplers in MDM applications. Experimentally, mode conversion from fundamental linear polarization (LP) mode LP01 to higher order LP11 mode in two-mode FBG (TMFBG) has been observed. Index asymmetry and electric field distortion induced by ultraviolet (UV) side illumination in fabrication of FBG make the two modes no longer orthogonal. However, its spectrum analysis mainly depends on experimental data and software simulation using the complex finite element method (FEM). Here a simpler theoretical model based on coupled mode theory (CMT) and Runge-Kutta method (RKM) is proposed. An analytical expression of the mode coupling coefficient is derived and the modeling results match very well with experimental data. Abrupt fiber tapers allow power transfer between core and cladding modes and show promise as RI sensing components when two abrupt tapers are cascaded into an in-line Mach-Zehnder interferometer (MZI). The main advantage of the MZI taper sensor is its low manufacturing cost. However, the optical spectrum analyzer (OSA) used as the receiver and demodulation device in the conventional setup is still expensive. Three simplified schemes of fiber taper MZI RI sensor systems are designed and demonstrated experimentally. The transmitter and the demodulation devices for the three schemes are a single wavelength laser and a photodetector (PD), two modulated lasers and a PD together with data acquisition and processing module, and a broadband source (BBS) and a PD together with matched MZI, respectively. In all those implementations OSA is not required, which significantly lowers the cost and leads to easy integration. Although extra modulation/demodulation devices are required, the second implementation has the best performance. Automatic operation is realized by LabVIEW programming. High sensitivity (2371 mV/RI unit (RIU)) and high stability are achieved experimentally. Those new schemes have great potential to be applied to other interferometric optic sensor systems. / Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2014-05-09 11:44:44.837

In this thesis, miniaturized wavelength interrogators based on planar lightwave circuits (PLCs) are investigated and developed for the optical fiber sensing applications in the aircraft structural health monitoring (SHM) and optofluidic analysis. Two interrogation systems based on an arrayed waveguide grating (AWG) and an Echelle diffractive grating (EDG) are developed and used to convert the optical sensing signals into strain, temperature, vibration, damage, and humidity information for the aircraft SHM. A fiber Bragg grating (FBG) sensing system using developed interrogators is then demonstrated in a field test for aircraft SHM applications. For optofluidic analysis, a PLCs based optofluidic device consisting of two on-chip lens sets is built to enhance the optical manipulation capability of particles. Then, a solution to a multi-functional Lab-on-a-Chip platform for optofluidic analysis is proposed, which integrates the developed particle maneuvering device, grating-structured sensors, and miniaturized interrogators.

Die vorliegende Arbeit beschreibt die Entwicklung eines Drucksensorkatheters auf Basis von Faser-Bragg-Gittern. Dazu werden der medizinische Hintergrund aus technischer Sicht strukturiert dargelegt und bereits verfügbare Messmethoden für Manometrieuntersuchungen erörtert. Der Stand der Technik bei Faser-Bragg-Gitter basierten Sensoren und deren Auswertegeräten wird im Zusammenhang mit den aus dem medizinischen Hintergrund und dem Vergleich mit den anderen Messmethoden erwachsenden Anforderungen dargestellt. Die Entwicklung eines zweistufigen für die Herstellung mittels Koextrusion geeigneten Mantels für die optischen Fasern wird beschrieben. Mehrere Funktionsmuster für einen Drucksensorkatheter werden experimentell charakterisiert und die Ergebnisse hinsichtlich der Medizineignung bewertet.

Ces trois années de thèse balayent la conception, la fabrication et la caractérisation de lasers III V sur silicium à 1.31 µm pour les data-communications. Le design des sources englobe notamment l’optimisation du couplage entre l’empilement III V et le silicium, effectué grâce à un taper adiabatique, ainsi que l’étude de la cavité laser inscrite, comme le taper, dans le silicium. Trois types de cavités à base de réseaux ont été étudiées: les cavités à contre-réaction distribuée (DFB pour distributed feedback), celles à réseaux de Bragg distribuées (DBR pour distributed Bragg reflector) et enfin celles à réseaux de Bragg échantillonnées (SGDBR pour sampled-grating DBR). Deux solutions ont été abordées concernant les lasers DFB: le réseau, inscrit dans le guide silicium sous la zone de gain, est soit gravé au-dessus du guide Si, soit sur les côtés. La seconde possibilité, appelée ‘DFB lasers couplés latéralement’, simplifie la fabrication et élargit les possibilités de design.Les lasers DFB fabriqués sont très prometteurs en terme de puissance (avec jusque 20 mW dans le guide) ainsi que pour leur pureté spectrale (avec une différence de plus de 50 dB entre le mode principal et le mode suivant). Une accordabilité spectrale de plus de 27 nm a été obtenue en continu avec les lasers SGDBR tout en conservant une très bonne pureté spectrale et une puissance de plus de 7 mW dans le guide. / This 3 years work covers the design, the process and the characterization of III-V on silicon lasers at 1.31 µm for datacommunication applications. In particular, the design part includes the optimization of the coupling between III V and Si using adiabatic tapers as well as the laser cavity, which is formed within the Si. Three types of lasers were studied, all of them based on cavities which consist of gratings: distributed feedback (DFB) lasers, distributed Bragg reflector (DBR) lasers and finally sampled-grating DBR (SGDBR) lasers. Regarding the DFB lasers, two solutions have been chosen: the grating is either etched on top or on the edges of the Si waveguide to form so called vertically or laterally coupled DFB lasers. The latter type, quite uncommon among hybrid III V on Si technologies, simplifies the process fabrication and broadens the designs possibilities.Not only the lasers demonstrated show high output powers (~20 mW in the waveguides) but also very good spectral purities (with a side mode suppression ratio higher than 50 dB), especially for the DFB ones. The SGDBR devices turn out to be continuously tunable over a wavelength range higher than 27 nm with a good spectral purity as well and an output power higher than 7 mW in the waveguide with great opportunities of improvement.

Thanks to its compatibility with the current CMOS technology and its potential of seamless integration with electronics, silicon photonics has been attracting an ever-increasing interest in recent years from both the academia and industry. By applying silicon photonic technology in microwave photonics, on-chip integration of microwave photonic systems could be implemented with improved performance including a much smaller size, better stability and lower power consumption. This thesis focuses on developing silicon-based photonic integrated circuits for microwave photonic applications. Two types of silicon-based on-chip devices, waveguide Bragg gratings and optical micro-cavity resonators, are designed, developed, and characterized, and the use of the developed devices in microwave photonic applications is studied. After an introduction to silicon photonics and microwave photonics in Chapter 1 and an overview of microwave photonic signal generation and processing in Chpater2, in Chapter 3 a silicon-based on-chip phase-shifted waveguide Bragg grating (PS-WBG) is designed, fabricated and characterized, and its use for the implementation of a photonic temporal differentiator is experimentally demonstrated. To have a waveguide grating that is wavelength tunable, in Chapter 4 a tunable waveguide grating is proposed by incorporating a PN junction across the waveguide grating, to use the free-carrier plasma dispersion effect in silicon to achieve wavelength tuning. The use of a pair of wavelength-tunable waveguide gratings to form a wavelength-tunable Fabry-Perot resonator for microwave photonic signal processing is studied. Thanks to its electrical tunability, a high-speed electro-optic modulator, a tunable fractional-order photonic temporal differentiator and a tunable optical delay line are experimentally demonstrated. To increase the bandwidth of a waveguide grating, in Chapter 5 a linearly chirped waveguide Bragg grating (LC-WBG) is designed, fabricated and evaluated. By incorporating two LC-WBGs in two arms of a Mach-Zehnder interferometer (MZI) structure, an on-chip optical spectral shaper is produced, which is used in a photonic microwave waveform generation system based on spectral-shaping and wavelength-to-time (SS-WTT) mapping for linearly chirped microwave waveform (LCMW) generation. To enable the LC-WBG to be electrically tuned, in Chapter 6 a lateral PN junction is introduced in the grating and thus an electrically tunable LC-WBG is realized. By incorporating two tunable LC-WBGs in a Michelson interferometer structure, an electrically tunable optical spectral shaper is made. By applying the fabricated spectral shaper in an SS-WTT mapping system, a continuously tunable LCMW is experimentally generated. Compared with a waveguide Bragg grating device, an on-chip optical micro-cavity resonator usually has a much smaller dimension, which is of help to increase the integration density and reduce the power consumption. Different on-chip optical micro-cavity resonators are studied in this thesis. In Chapter 7, an on-chip symmetric MZI incorporating multiple cascaded microring resonators is proposed. By controlling the radii of the rings, the MZI could be designed to have a spectral response with a linearly-varying free spectral range (FSR), which could be used in photonic generation of an LCMW, and to have a multi-channel spectral response with identical channel spacing, which could be used in the implementation of an independently tunable multi-channel fractional-order temporal differentiator. To further reduce the footprint of an optical micro-cavity resonator, in Chapter 8 an ultra-compact microdisk resonator (MDR) with a single-mode operation and an ultra-high Q-factor is proposed, fabricated and evaluated, and its use for the implementation of a microwave photonic filter and an optical delay line is experimentally demonstrated. To enable the MDR to be electrically tunable, in Chapter 9 an electrically tunable MDR is realized by incorporating a lateral PN junction in the disk. The use of the fabricated MDR in microwave photonic applications such as a high-speed electro-optic modulator, a tunable photonic temporal differentiator and a tunable optical delay line is experimentally demonstrated.

In this thesis, miniaturized wavelength interrogators based on planar lightwave circuits (PLCs) are investigated and developed for the optical fiber sensing applications in the aircraft structural health monitoring (SHM) and optofluidic analysis. Two interrogation systems based on an arrayed waveguide grating (AWG) and an Echelle diffractive grating (EDG) are developed and used to convert the optical sensing signals into strain, temperature, vibration, damage, and humidity information for the aircraft SHM. A fiber Bragg grating (FBG) sensing system using developed interrogators is then demonstrated in a field test for aircraft SHM applications. For optofluidic analysis, a PLCs based optofluidic device consisting of two on-chip lens sets is built to enhance the optical manipulation capability of particles. Then, a solution to a multi-functional Lab-on-a-Chip platform for optofluidic analysis is proposed, which integrates the developed particle maneuvering device, grating-structured sensors, and miniaturized interrogators.

L'industrie nucléaire montre un intérêt croissant pour les technologies basées sur les fibres optiques pour la transmission des données et comme capteurs. Les fibres optiques offrent plusieurs avantages et les capteurs utilisant cette technologie n'ont pas besoin d'alimentation électrique au point de détection, ils ont une réponse rapide et peuvent être facilement multiplexés : dans le cas d'un capteur de température plusieurs thermocouples peuvent être substituées par une seule fibre, diminuant les déchets. Les réacteurs à fission nucléaire constituent un des environnements les plus agressifs : la dose de rayonnement gamma est de l'ordre du GGy avec une forte fluence de neutrons et une température de fonctionnement supérieure à 300°C pour les réacteurs actuels, connus comme de génération III. Ce travail a été réalisé en collaboration avec la société AREVA, industriel français actif dans le domaine de l'énergie, dans le but de réaliser un capteur de température résistant à l'environnement d'un réacteur nucléaire de génération IV, réacteur à neutrons rapides refroidi au sodium liquide. La technologie actuellement utilisée, les thermocouples, présente une dérive de la mesure due au rayonnement et un temps de réponse d'une seconde. Afin de supprimer la dérive, de réduire le temps de réponse et d'augmenter la précision, un capteur de température à réseau de Bragg a été choisi. Pour comprendre le comportement d'un tel système dans un environnement difficile, nous avons utilisé une approche expérimentale basée sur des techniques complémentaires comme l'atténuation induite par le rayonnement, photoluminescence, résonance paramagnétique électronique et spectroscopie Raman / The nuclear industry shows an increasing interest in the fiber optic technology for both data communication and sensing applications in nuclear plants. The optical fibers offer several advantages and the sensors based on this technology do not need any electrical power at the sensing point, they have a quick response and they can be easily multiplexed: in the case of a temperature sensor, several thermocouples can be substituted by a single fiber, resulting in a decrease of the waste material. The fission reactors are a very harsh environment: it is characterized by the highest dose of gamma-rays, of the order of magnitude of GGy, besides a high flux of neutrons and high operating temperature (300°C for the current reactors, known as generation III). This work has been carried out in collaboration with AREVA, a French industrial conglomerate active in the energy domain, with the aim of realizing a temperature sensor resistant to the environment of nuclear reactor of generation IV, in particular a Sodium-cooled Fast Reactor. The currently used technology, the thermocouples, presents a drift of the measurement due to irradiation, that needs a calibration, and a long response time on the order of seconds. In order to remove the drift, to reduce the response time and to increase the precision, a Fiber Bragg Grating temperature sensor was chosen, in regard to all the advantages of the optical fibers. To understand the behavior of such system in a harsh environment, as the nuclear reactor core, we used an experimental approach based on complementary techniques such as radiation-induced attenuation, photoluminescence, electron paramagnetic resonance and Raman spectroscopies