Dissertations / Theses on the topic 'Specialty optical fibers'

Orientador: Cristiano Monteiro de Barros Cordeiro
Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin
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Resumo: Nesta tese, fibras ópticas especiais são estudadas para fins de sensoriamento. Primei-ramente, propomos a estrutura denominada fibra capilar com núcleo embutido (embedded-core capillary fibers) para realização de sensoriamento de pressão. Estudos numéricos e analíticos foram realizados e mostraram que altas sensibilidades a variações de pressão poderiam ser al-cançadas com esta estrutura simplificada, que consiste de um capilar dotado de um núcleo, dopado com germânio, em sua parede. Experimentos permitiram medir uma sensibilidade de (1.04 ± 0.01) nm/bar, que é um valor alto quando comparado a outros sensores de pressão ba-seados em fibras microestruturadas. Ademais, estudamos fibras do tipo surface-core, que são fibras cujos núcleos são colocados na superfície externa da fibra. Nesta abordagem, redes de Bragg foram utilizadas para obter sensores de índice de refração ¿ fazendo-se uso da interação entre o campo evanescente do modo guiado no núcleo e o ambiente externo à fibra ¿ e de cur-vatura ¿ ao se explorar o fato de que, nestas fibras, o núcleo se encontra fora do centro geomé-trico da mesma. As sensibilidades a variações de índice de refração e curvatura medidas, 40 nm/RIU em torno de 1.41 e 202 pm/m-1 comparam-se bem a outros sensores baseados em redes de Bragg. Outrossim, fibras capilares poliméricas foram investigadas como sensores de temperatura e pressão. Para a descrição do sensor de temperatura, usou-se um modelo analítico para simular o espectro de transmissão dos capilares e a sua dependência com as variações de temperatura. No que tange à aplicação de sensoriamento de pressão, variações nas espessuras dos capilares devido à ação da pressão foram calculadas e relacionadas à sensibilidade da me-dida de monitoramento. Nestas duas aplicações, realizações experimentais também são repor-tadas. Finalmente, oportunidades adicionais de sensoriamento ao se utilizar fibras ópticas es-peciais são apresentadas, a saber, um sensor de pressão para dois ambientes baseados em fibras de cristal fotônico, um sensor de três parâmetros baseado em redes de Bragg, fibras afinadas e interferência multimodal, um sensor de nível de líquido baseado em redes de Bragg e interfe-rência multimodal e um sensor de temperatura baseado em fibras embedded-core preenchidas com índio. Os resultados aqui reportados demonstram o potencial das fibras ópticas em forne-cerem plataformas de sensoriamento para alcançar medidas de diferentes tipos de parâmetros com alta sensibilidade e resolução adequada
Abstract: In this thesis, specialty optical fibers for sensing applications are investigating. Firstly, we propose the embedded-core capillary fiber structure for acting as a pressure sensor. Analyt-ical and numerical studies were performed and showed that high pressure sensitivity could be achieved with this simplified fiber structure, which consists of a capillary structure with a germanium-doped core placed within the capillary wall. Experiments allowed measuring a sensitivity of (1.04 ± 0.01) nm/bar, which is high when compared to other microstructured optical fiber-based pressure sensors. Moreover, we studied the so-called surface-core optical fibers, which are fibers whose cores are placed at the external boundary of the fiber. In this approach, Bragg gratings were used to obtain refractive index ¿ making use of the interaction between the guided mode evanescent field and the external medium ¿ and directional curva-ture sensors ¿ by exploring the off-center core position. The measured refractive index and the curvature sensitivities, respectively 40 nm/RIU around 1.41 and 202 pm/m-1, compares well to other fiber Bragg grating-based sensors. Additionally, antiresonant polymer capillary fibers were investigated as temperature and pressure sensors. For the temperature sensing descrip-tion, one used an analytical model to simulate the transmission spectra of such fibers and the dependence on temperature variations. Regarding the pressure sensing application, pressure-induced capillary wall thickness variations were analytically accounted and related to the sys-tem pressure sensitivity. In both these applications, experimental data were presented. Finally, additional opportunities using specialty optical fibers were presented, namely, a photonic-crystal fiber-based dual-environment pressure sensor, a three parameters sensor using Bragg gratings, tapered fibers and multimode interference, a liquid-level sensor based on Bragg grat-ings and multimode interference, and a temperature sensor based in an embedded-core fiber filled with indium. The results reported herein demonstrates the potential of optical fibers for providing sensing platforms to attain measurements of different sort of parameters with highly sensitivity and improved resolutions
Doutorado
Física
Doutor em Ciências
152993/2013-4
CNPQ

Although optical fibers and specialty waveguides are the base of majority of today's telecom and light delivery applications, fabrication deformation, nonlinearity and attenuation limit the bandwidth of the data being transmitted or the amount of power carried by these systems. One-way to overcome these limitations without changing the fibers design or fabrication is to engineer the input light in order to excite a certain mode or a group of modes with unique optical properties. Diffractive and micro optics are highly effective for selectively coupling light to specific modes. Using micro optics, mode selective coupling can be achieved through several matching schemes: phase only, phase and amplitude, or phase, amplitude and polarization. The main scope of this work is the design and fabrication of novel optical elements that overcome the limitations of these light delivery systems, as well as the characterization and analysis of their performance both experimentally and using numerical simulation
Ph.D.
Other
Optics and Photonics
Optics

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Nonlinear effects are essential for the construction of photonic devices such as modulators, optical switches and frequency converters. Aiming at the development of devices for optical frequency conversion and the generation of nonclassical states of light in photonic chips, this thesis presents the design and simulation of a frequency converter based on second harmonic generation controlled by static electric field in a silicon nitride ring resonator. The developed simulation appraises conversion efficiencies up to -8.25 dB with the advantage to provide an electrical interface to control the conversion. Optical fiber based devices are also within the scope of the thesis and a new technique is presented for manufacturing optical fibers with enhanced nonlinear response by the presence of metallic gold nanoparticles. The manufactured fibers are based on silica that is doped with aluminum and gold in the core, offering full compatibility and integration with conventional optical fibers. The nanoparticles were created by annealing in an oven or by heating with a CO2 laser beam, which offers unprecedented control over particle size and density in optical fibers. Compared to previously reported fibers with gold nanoparticles, higher concentration of nanoparticles were obtained which was estimated by the plasmonic absorption peak exceeding 800 dB/m and by a consequent increasing in the nonlinear refractive index of at least 50x under continuous wave excitation, achieving values of n2=(6,75±0,55)×10-15 m²/W. The development of these fibers and the design of the on chip frequency converter provide platforms for the development of efficient and integrated devices in fiber based optical systems and in photonic chips.
Efeitos não lineares são essenciais para construção de dispositivos fotônicos como moduladores, chaves ópticas e conversores de frequências. Esta tese apresenta o projeto e a simulação de um conversor de frequências baseado na geração de segundo harmônico controlado por campo elétrico estático em um ressonador em anel de nitreto de silício, visando o desenvolvimento de dispositivos para conversão de frequências ópticas e geração de estados não clássicos da luz em chips fotônicos. A simulação desenvolvida prevê eficiência de conversão de até -8,25 dB com o diferencial de oferecer uma interface elétrica no controle de conversão. Dispositivos baseados em fibras ópticas também são visados nesta tese e uma nova técnica para fabricação de fibras ópticas com resposta não linear aumentada pela presença de nanopartículas metálicas de ouro é apresentada. As fibras fabricadas são baseadas em sílica com dopagem de alumínio e ouro no núcleo, possuindo total compatibilidade de integração com fibras ópticas convencionais. As nanopartículas foram sintetizadas através de tratamentos térmicos em forno ou aquecimento com feixe laser de CO2, obtendo-se um controle sem precedentes das dimensões e densidade de nanopartículas em fibras ópticas. Comparadas às fibras previamente reportadas na literatura, foram obtidas maiores concentrações de nanopartículas estimadas por picos de absorções plasmônicas maiores que 800 dB/m e por um consequente aumento no índice de refração não linear de pelo menos 50x no regime de onda contínua, obtendo-se valores de n2=(6,75±0,55)×10-15 m²/W. O desenvolvimento dessas fibras e o projeto do ressonador em anel para conversão de frequências oferecem plataformas para o desenvolvimento de dispositivos eficientes e integrados para sistemas ópticos baseados em fibras ópticas e em chips fotônicos.

Thanks to their capability of transmitting light with low loss, optical fibers have found a wide range of applications in illumination, imaging, and telecommunication. However, since the light guided in a regular optical fiber is well confined in the core and effectively isolated from the environment, the fiber does not allow the interactions between the light and matters around it, which are critical for many sensing and actuation applications. Specially shaped optical fibers endow the guided light in optical fibers with the capability of interacting with the environment by modifying part of the fiber into a special shape, while still preserving the regular fiber’s benefit of low-loss light delivering. However, the existing specially shaped fibers have the following limitations: 1) limited light coupling efficiency between the regular optical fiber and the specially shaped optical fiber, 2) lack special shape designs that can facilitate the light-matter interactions, 3) inadequate material selections for different applications, 4) the existing fabrication setups for the specially shaped fibers have poor accessibility, repeatability, and controllability. The overall goal of this dissertation is to further the fundamental understanding of specially shaped fibers and to develop novel specially shaped fibers for different applications. In addition, the final part of this dissertation work proposed a microfluidic platform that can potentially improve the light-matter interactions of the specially shaped fibers in fluidic environments. The contributions of this dissertation work are summarized as follows: 1) An enhanced fiber tapering system for highly repeatable adiabatic tapered fiber fabrications. An enhanced fiber tapering system based on a novel heat source and an innovative monitoring method have been developed. The novel heat source is a low-cost ceramic housed electric furnace (CHEF). The innovative monitoring method is based on the frequency-domain optical transmission signal from the fiber that is being tapered. The enhanced fiber tapering system can allow highly repeatable fabrication of adiabatically tapered fibers. 2) A lossy mode resonance (LMR) sensor enabled by SnO2 coating on a novel specially shaped fiber design has been developed. The developed LMR sensor has a D-shape fiber tip with SnO2 coating. It has the capability of relative humidity and moisture sensing. The fiber-tip form factor can allow the sensor to be used like a probe and be inserted into/removed from a tight space. 3) Specially shaped tapered fibers with novel designs have been developed for integrated photonic and microfluidic applications. Two novel specially tapered fibers, the tapered fiber loop and the tapered fiber helix have been developed. The tapered fiber loop developed in this work has two superiority that differentiated itself from previous works: a) the mechanical stability of the tapered fiber loop in this work is significantly better. b) the tapered fiber loops in this work can achieve a diameter as small as 15 ?m while still have a high intrinsic optical quality factor of 32,500. The tapered fiber helix developed in this work has a 3D structure that allows it to efficiently deliver light to locations out of the plane defined by its two regular fiber arms. Applications of the tapered fiber helices in both integrated photonic device characterizations and microparticle manipulations have been demonstrated. 4) Developed an acrylic-tape hybrid microfluidic platform that can allow function reconfiguration and optical fiber integration. A low-cost, versatile microfluidic platform based on reconfigurable acrylic-tape hybrid microfluidic devices has been developed. To the best of the author’s knowledge, this is the first time that the fabrication method of sealing the acrylic channel with a reconfigurable functional tape has been demonstrated. The tape-sealing method is compatible with specially shaped fiber integrations.

At the Dawn of the 21st century, the field of specialty optical fibers experienced a scientific revolution with the introduction of the stack-and-draw technique, a multi-steps and advanced fiber fabrication method, which enabled the creation of well-controlled micro-structured designs. Since then, an extremely wide variety of finely tuned fiber structures have been demonstrated including novel materials and novel designs. As the complexity of the fiber design increased, highly-controlled fabrication processes became critical. To determine the ability of a novel fiber design to deliver light with properties tailored according to a specific application, several mode analysis techniques were reported, addressing the recurring needs for in-depth fiber characterization. The first part of this dissertation details a novel experiment that was demonstrated to achieve modal decomposition with extended capabilities, reaching beyond the limits set by the existing mode analysis techniques. As a result, individual transverse modes carrying between ~0.01% and ~30% of the total light were resolved with unmatched accuracy. Furthermore, this approach was employed to decompose the light guided in Large-Mode Area (LMA) fiber, Photonic Crystal Fiber (PCF) and Leakage Channel Fiber (LCF). The single-mode performances were evaluated and compared. As a result, the suitability of each specialty fiber design to be implemented for power-scaling applications of fiber laser systems was experimentally determined. The second part of this dissertation is dedicated to novel specialty fiber laser systems. First, challenges related to the monolithic integration of novel and complex specialty fiber designs in all-fiber systems were addressed. The poor design and size compatibility between specialty fibers and conventional fiber-based components limits their monolithic integration due to high coupling loss and unstable performances. Here, novel all-fiber Mode-Field Adapter (MFA) devices made of selected segments of Graded Index Multimode Fiber (GIMF) were implemented to mitigate the coupling losses between a LMA PCF and a conventional Single-Mode Fiber (SMF), presenting an initial 18-fold mode-field area mismatch. It was experimentally demonstrated that the overall transmission in the mode-matched fiber chain was increased by more than 11 dB (the MFA was a 250 ?m piece of 50 ?m core diameter GIMF). This approach was further employed to assemble monolithic fiber laser cavities combining an active LMA PCF and fiber Bragg gratings (FBG) in conventional SMF. It was demonstrated that intra-cavity mode-matching results in an efficient (60%) and narrow-linewidth (200 pm) laser emission at the FBG wavelength. In the last section of this dissertation, monolithic Multi-Core Fiber (MCF) laser cavities were reported for the first time. Compared to existing MCF lasers, renown for high-brightness beam delivery after selection of the in-phase supermode, the present new generation of 7-coupled-cores Yb-doped fiber laser uses the gain from several supermodes simultaneously. In order to uncover mode competition mechanisms during amplification and the complex dynamics of multi-supermode lasing, novel diagnostic approaches were demonstrated. After characterizing the laser behavior, the first observations of self-mode-locking in linear MCF laser cavities were discovered.
Ph.D.
Doctorate
Optics and Photonics
Optics and Photonics
Optics and Photonics

Special optical fibres are introduced with the emphasis on rare-earth-doped fibres and fibres with crystal-like properties. Characterisation techniques for these types of fibre are discussed and several applications are described. In particular, optical time-domain reflectometry is used to demonstrate a distributed temperature sensor based on the temperature dependence of the absorption in rare-earth-doped fibres. Further, energy transfer between ytterbium and erbium is characterised and an erbium fibre laser sensitised with ytterbium is demonstrated. Finally, techniques for the creation of crystal-like properties in optical fibres are developed and second-order nonlinear phenomena in these fibres are analysed both experimentally and theoretically.

Malgré d'importantes percées dans le domaine de la biodétection, nous avons toujours besoin de nouveaux capteurs qui faciliteraient la détection précoce de maladies graves comme le cancer. La biopsie tissulaire classique reste la référence dans de nombreux cas. Bien que cette approche ait montré son potentiel, elle reste invasive pour les patients et les techniques de détection sont fastidieuses ou manquent de sensibilité pour détecter la maladie à un stade précoce. La spectroscopie Raman a démontré son intérêt pour la biodétection. Sa capacité à caractériser la nature chimique, la structure et l'orientation d'un analyte, en fait un candidat idéal. Les pics Raman très nets d'une molécule peuvent être considérés comme une véritable empreinte digitale. Malheureusement, le signal Raman diffusé est extrêmement faible. Cette limitation a été surmontée par la spectroscopie Raman exaltée de surface (SERS), car elle augmente considérablement le signal Raman diffusé tout en maintenant la largeur des pics du spectre d'une molécule. Malheureusement, la plupart des substrats SERS actuels sont soit des surfaces métalliques nano-rugueuses en 2D soit des nanoparticules colloïdales, qui manquent de sensibilité et de fiabilité dans les mesures avec une faible répétabilité et reproductibilité des données. Ces dernières années, des fibres optiques spéciales ont été utilisées comme plateformes SERS. Elles comportent des trous qui s'étendent sur toute leur longueur. Ces trous permettent d'incorporer l'analyte à l'intérieur de la fibre. Ainsi, une telle plate-forme représente une alternative prometteuse aux substrats plans puisque l'analyte et la lumière d'excitation peuvent interagir sur une plus grande longueur à l'intérieur des fibres. De plus, les fibres optiques sont très flexibles, compactes, et permettent un guidage de la lumière à faible perte. Par conséquent, ces capteurs à fibres présentent à la fois les capacités de détection exceptionnelles du SERS, les avantages des fibres optiques et une sensibilité et une fiabilité améliorées. Dans ce manuscrit, nous visons à créer une plateforme de biodétection qui pourrait être utilisée dans un cadre clinique. Pour cela, nous proposons d'optimiser les caractéristiques d'une topologie de fibre déjà existante. Cela nous permet d'augmenter sa sensibilité tout en améliorant sa fiabilité et sa facilité d’utilisation. Grâce à ce capteur amélioré, nous avons pu pour la première fois détecter le biomarqueur du cancer de l'ovaire dans les fluides de kystes cliniques, ce qui nous a permis de différencier le stade du cancer. Par la suite, nous proposons une nouvelle topologie de fibre, spécifiquement conçue pour augmenter encore la sensibilité des sondes à fibre basées sur le SERS. Cette amélioration est réalisée en augmentant la surface d'interaction par rapport aux sondes à fibre standard. Pour cela, le diamètre du noyau est considérablement augmenté et la quantité de lumière qui interagit avec l'analyte est contrôlée avec précision. Nous envisageons que de tels capteurs à fibres fonctionnalisés puissent être incorporés à l'intérieur d'une aiguille de biopsie afin de créer un capteur deux-en-un pour la collecte et l’analyse de fluides corporels. Les limitations associées aux aiguilles de biopsie actuelles, qui exigent une collecte et une analyse des échantillons en deux étapes, pourraient ainsi être surmontées
Despite important breakthroughs in biosensing, we are still in need of new sensors that would facilitate the early detection of severe diseases such as cancer. Classical tissue biopsy remains the gold standard in many cases. Although this approach has shown its potential, it remains invasive for the patients and the detection techniques are either tedious or lack the sensitivity to detect the disease at an early stage. Raman spectroscopy has demonstrated its interests for biosensing. Its ability to characterize the chemical nature, structure and the orientation of an analyte makes it an ideal candidate. The sharp Raman peaks of a molecule can be seen as a true fingerprint. Regrettably, Raman scattered signal is extremely weak. This limitation was overcome by surface enhanced Raman spectroscopy (SERS), since it drastically increases the Raman scattered signal while maintaining the sharp peak of the fingerprint spectrum of a molecule. Unfortunately, most of the current SERS substrates are 2D nano-roughened metal surfaces or colloidal nanoparticles, which lack the sensitivity and reliability in measurement with poor repeatability and reproducibility in the data. In the recent years, special optical fibers have been used as SERS platforms. They feature holes that run along their entire length. These holes allow for the analyte to be incorporated inside the fiber. Thus, such platform represents a promising alternative to planar substrates since the analyte and the excitation light can interact for longer length inside the fibers. In addition, optical fibers are very flexible, compact and allow for low-loss light guiding. Therefore, such fiber sensors exhibit the outstanding detection abilities of SERS, the advantages of optical fibers and improved sensitivity and reliability. In this manuscript, we aim to create a biosensing platform that could be routinely used in a clinical setting. For that, we propose to optimize the features of an already reported fiber topology. This allows us to increase its sensitivity while simultaneously improving its reliability and practicability. With this improved sensor, for the first time, we could detect the biomarker for ovarian cancer in clinical cyst fluids, which allowed us to differentiate the stage of the cancer. Subsequently, we propose a novel fiber topology, specifically designed to further increase the sensitivity of SERS-based fiber probes. This is achieved by increasing the surface of interaction compared to standard fiber sensors. For that, the core diameter is significantly increased and the amount of light that interacts with the analyte is precisely controlled. We envision that such functionalized fiber sensors could be incorporated inside a biopsy needle to create a two-in-one sensor for body fluid collection and readout that can eventually overcome the limitations associated with existing biopsy needle platforms, which demands for two-step sample collection and readout

Recently, multimaterial optical fiber whose core and cladding's compositions are different materials attracts more and more attention of researchers in many countries. When using very different compositions of glasses, these fibers can present higher refractive index difference leading to strong nonlinear coefficient. We can extend use of material to metals, and link electrical and optical functions giving hybrid devices. In these thesis, after a presentation of well known fabrication processes and more original ones, we propose to develop the powder-in-tube method to fabricate two original fibers : first one is a solid core ARROW bandgap fiber with Lanthano Alumino Silicate glass as high index rod to realize a low transmission and bend loss fiber. Application can be in the field of high power laser transmission. The second fiber studied includes copper metallic wires. One microsize coaxial cable with improved structure was designed, modelized and realized to demonstrate the interest of such a structure up to 100 GHz and more. These two fibers mixed the powder in tube method with the well-known stack and draw process
Les fibres optiques « multimatériaux », sont définies comme des guides optiques où le cœur et la gaine de la fibre optique sont composés de matériaux de composition ou de nature différentes. Ces fibres attirent l'attention de plus en plus de chercheurs, et ce dans de nombreux pays, car selon les différentes compositions des verres, ces fibres optiques peuvent présenter des propriétés originales. Dans cette thèse , après une présentation des procédés de fabrication bien connus et d'autres plus originaux, nous proposons de développer le procédé « poudre » pour fabriquer deux fibres multimatériaux originales. La première est une fibre à bande interdite photonique composée d'un cœur de silice et d'un cristal photonique bidimensionnel d'inclusions d'un verre de Silice Aluminium Lanthane. Ce verre permet de développer ce type de fibre avec des inclusions dont l'indice de réfraction est plus important que la plupart des fibres à bande interdite rapportées. Les propriétés de ces fibres ont été étudiées ce qui à conduit à la conception et la fabrication d'une fibre optimisée. La deuxième fibre étudiée comprend des fils métalliques de cuivre. Nous avons étendu le procédé de fabrication aux fibres verre / métal. Un câble coaxial de taille micrométrique a été modélisé, optimisé et réalisé pour démontrer l'intérêt d'une telle structure pour guider des signaux micro-ondes à 100 GHz. Les procédés développés pour la fabrication des ces deux fibres associent le procédé « poudre » et le procédé « stack-and-draw »

Doctor of Philiosophy
This thesis presents my work in the area of optical fibre sensing, and optical fibre design and characterisation along with the interferometric and signal processing techniques that were developed along the way.

This thesis presents my work in the area of optical fibre sensing, and optical fibre design and characterisation along with the interferometric and signal processing techniques that were developed along the way.

Dans le cadre du projet Cigéo, stockage géologique des déchets radioactifs à vie longue, la surveillance des infrastructures contribuera à confirmer la récupérabilité des déchets, prévue sur des durées pluridécennales. Les structures sont apparentés à des tunnels horizontaux, sous 500 m de couverture. Leur convergence (réduction progressive de leur section) doit être mesurée par des systèmes peu intrusifs, sensibles, compatibles avec un environnement sévère. Une méthode inverse, utilisant un modèle par éléments finis, a été développée pour déterminer la convergence à partir de mesures réparties de déformations acquises par rétrodiffusion Rayleigh et Brillouin dans des câbles à fibre optique. Elle a été validée sur un démonstrateur d’alvéole, au laboratoire en surface et en souterrain. Sur une échelle de 10 mm représentative de l’application, la convergence est déterminée à 1 mm près par les fibres optiques, proche des capteurs de référence. La sensibilité à la mise en œuvre, au chargement, au bruit de mesure, a été étudiée. La tenue des fibres optiques à l’impact couplé des radiations et de la température a été étudiée pour des fibres optique en revêtement primaire: une dose totale de 1 MGy dégrade moins la mesure de déformation à 100 °C qu’à température ambiante. La fibre optique la plus résistance a été placée dans un câble de mesure de déformations, soumis à des radiations gamma et des sollicitations thermiques. Les coefficients de sensibilité thermique et mécanique des rétrodiffusions Brillouin et Rayleigh restent stables après 500 kGy, ainsi que ses caractéristiques mécaniques du câble. L’étude a aussi permis de quantifier les processus de plasticité, jusqu’à 10000 με
In the framework of Cigéo, the future underground repository for long-lived radioactive waste, the monitoring of the structures must be guaranteed for almost a century to ensure its reversibilit. The horizontal repository cells will be loaded by 500 m of rock which will reduce their section over time. This reduction, called convergence, must be monitored by sensors with resistance to harsh environment, low intrusiveness, proper sensitivity. We propose the use of distributed optical fiber strain sensing cables, whose strain measurements are used to calculate convergence via an inverse-analysis finite-element method, using Brillouin and Rayleigh backscatterings. The method is described, assessing the influence of structural parameters and measurements noise on its sensitivity. We validate it in a laboratory test, in controlled conditions and underground, reproducing convergences up to the representative value of 10 mm on a mock-up of the high-level waste repository cell. We compare two fixation methods and loading schemes, using other sensors as reference. Results show how distributed optical fiber sensors can achieve the required 1 mm of resolution, close to standard methods. The fibers have been firstly analysed under the coupled effect of temperature and radiation up to a total γ-rays dose of 1 MGy. Temperatures around 100°C preserve the fiber functioning better than being at room temperature. A specific cable for strain sensing, with a radiation resistant fiber inside, is then developed and tested, reporting that temperature and strain sensitivities and the mechanical behaviour remain stable up to 500 kGy. We evaluate also the role of the protective layers of the tested cable and its plastic behaviour up to 10000 με

L'objectif de ce travail de recherche est l'étude, la réalisation et la caractérisation d'un amplificateur de puissance à base de verres spéciaux devant être inséré dans un dispositif laser impulsionnel à cohérence élevée opérant a la longueur d'onde de 1550 nm en configuration MOPA (Master Oscillator Power Amplifier). Il aura pour fonction d'amplifier le signal provenant d'un laser source afin de pouvoir le propager sur des distances élevées sans pour autant dégrader ses caractéristiques spectrales ou sa cohérence. Le dispositif ainsi obtenu sera utilisé comme source laser pour des systèmes LIDAR compact pouvant soit être embarqués à bord d'avions ou de voitures; soit être utilisés dans des stations météorologiques ou des aéroports. Un tel projet représente une innovation majeure dans le domaine des capteurs laser fonctionnant en espace libre. Il s'agit en effet de réaliser des dispositifs compacts qui n'existent pour l'instant pas aussi bien de façon commerciale que des les laboratoires de recherche
The objective of the present research is the study, fabrication and characterization of a power amplifier based on special glasses to be implemented as an embedded module inside a pulsed laser device with high coherence working at 1550 nm wavelength. The optical amplifier represents the second module of a laser in configuration MOPA (Master Oscillator Power Amplifier). The device must amplify the signal proceeding from a seed laser and allow the propagation of the signal at high distances while maintaining the spectral characteristics of the high coherent source. The device obtained with this approach will be employed as a source for a monitoring LIDAR system, which will be installed in train monitoring portals. The results can be extended to other applications as well, such as aeroplanes, meteorological stations or airports. The current research work is intended to contribute to the fabrication of compact devices that seems not be still available even in laboratories
Lo scopo della presente ricerca `e lo studio, la realizzazione e la caratter-izzazione di un amplificatore di potenza a base di vetri speciali da utiliz-zare come modulo da implementare all’interno di un dispositivo laser adimpulsi ad elevata coerenza operante alla lunghezza d’onda di 1550 nm.L’amplificatore ottico rappresenta il secondo modulo di un laser in configu-razione MOPA (Master Oscillator Power Amplifier): esso ha la funzione diamplificare il segnale proveniente da un laser “seed” e permette di propa-gare il suo segnale ad elevate distanze, mantenendo tuttavia le caratteris-tiche spettrali di elevata coerenza della sorgente. Il dispositivo cos`ı ottenutosar`a utilizzato come sorgente per un sistema LIDAR di rilevazione a bordodi aerei, autoveicoli e stazioni meteorologiche o aeroporti. Questi sistemisembrano non essere ancora disponibili neanche a livello dei laboratori diricerca

In this thesis some novel designs of photonic crystal fibers and rectangular waveguides have been reported for the applications: i) in which the nonlinearity need to be eliminated (such as high power fiber lasers and amplifiers); ii) in which the nonlinearity need to be enhanced (such as supercontinuum and slow light generation). Large mode area photonic crystal fiber designs for high power fiber lasers and amplifiers have been achieved by tailoring the size of the air holes and introducing down doped fused silica rods in the selective air holes in the cladding region of the structures. The proposed designs offer effective single-mode operation even with large core size. Effective single-mode operation provides good beam quality at the output of fiber lasers. In the case of LMA waveguide design the trenches of lower refractive index in cladding region have been introduced in such a way that all the propagating modes become leaky. The basic principle behind the cladding profiles is to introduce the high leakage loss to the higher order modes while nominal leakage loss to the fundamental mode, which makes the design effectively single-moded. Supercontiuum generation (the creation of broadband spectral components when an intense laser pulse passes through a highly nonlinear medium) is an area of exciting research that has been attracting scientific interest over last several decades. The midinfrared spectral domain ranging from 2 – 15 μm is mainly important because of not only it contains two important windows (3 – 5 μm and 8 – 13 μm) in which the earth’s atmosphere is relatively transparent but also the strong characteristic vibration transitions of most of the molecules in this domain. Mid-infrared molecular ‘fingerprint region’ is applicable in various important applications in different diverse fields such as medical, industry, security and astronomy. In this thesis a sincere attempt has been done to design and analyze the dispersion engineered photonic crystal fibers and rib waveguide geometries for ultra broadband mid-infrared supercontinuum sources. Ever increased supercontinuum spectrum spanning 2 – 15 μm in As2Se3 based chalcogenide photonic crystal fiber and rib waveguide has been achieved using femtosecond laser Abstract viii source of relatively low peak power. Such ultra broadband supercontinuum spectrum has also been achieved using equiangular spiral photonic crystal fiber geometry. Slow light with tunable features is investigated in doped and undoped tellurite fibers and As2Se3 based photonic crystal fiber geometries for telecommunication and computing applications. The maximum time delay up to 137 ns can be obtained using 1 meter long photonic crystal fiber pump with 100 mW. All the PCF and waveguide designs which are applicable for supercontinuum and slow light generation have been designed such that the propagating mode is strongly confined in small core of the structure, which makes the designs highly nonlinear.

This thesis work aims to design and modeling of specialty optical fibers for supercontinuum generation. Some novel photonic crystal fiber designs have been explored for the study of supercontinuum generation using highly nonlinear materials such as silica, tellurite, chalcogenide, and organic liquids in shorter fiber length with low input peak power and also focused on the coherence property to enhance the bandwidth of the supercontinuum broadband in the visible, near and mid-infrared wavelength regions. Supercontinuum generation arises due to broadening of the high-intensity ultra-short pulses in a nonlinear optically active medium due to self-phase modulation, cross-phase modulation, solitons, high order dispersion, stimulated Raman scattering, self-steepening, and some optical losses. The various potential applications of supercontinuum sources include cancer detection, medical imaging, gas sensing, optical coherence tomography, wavelength-division multiplexing, spectroscopy, and metrology. In this thesis, some sincere efforts have been made to numerically design the dispersion engineered photonic crystal fiber designs for supercontinuum generation in the visible, near, and mid-infrared wavelength regions. The computational analysis of the proposed fiber designs is based on the finite element method. We have tried to optimize the dispersion characteristics to reduce the effect of dispersion at the pump wavelength by tweaking the respective geometrical parameters of the core and cladding and also by changing the material composition in the core region. We have numerically analyzed the influence of input peak power, pulse width, peak power, and coherence on the supercontinuum broadening. The proposed silica-based photonic crystal fibers can generate the broad supercontinuum spectrum of bandwidth 0.67 µm to 2.4 µm in the visible and the near-infrared wavelength region at low input power in shorter fiber length. Some newly reported chalcogenide glasses V have been numerically investigated for the ultra-broadband supercontinuum generation in the infrared wavelength region. We have attained the supercontinuum spanning, 1 µm to 14 µm and 2 µm to 11 µm in photonic crystal fibers composed of Ga-Sb-S and GAP-Se chalcogenides respectively. In a tellurite based photonic crystal fiber, we achieved a broadband supercontinuum ranging, 1 µm to 5.5 µm. We have also proposed a photonic crystal fiber based on liquid infiltration to increase the nonlinearity in silica fibers and able to produce highly coherent supercontinuum broadband of spanning, 1 µm to 2.6 µm in the near-infrared wavelength region by using a few centimeters fiber length with low peak power.

This thesis work aims to design and modeling of specialty optical fibers for supercontinuum generation. Some novel photonic crystal fiber designs have been explored for the study of supercontinuum generation using highly nonlinear materials such as silica, tellurite, chalcogenide, and organic liquids in shorter fiber length with low input peak power and also focused on the coherence property to enhance the bandwidth of the supercontinuum broadband in the visible, near and mid-infrared wavelength regions. Supercontinuum generation arises due to broadening of the high-intensity ultra-short pulses in a nonlinear optically active medium due to self-phase modulation, cross-phase modulation, solitons, high order dispersion, stimulated Raman scattering, self-steepening, and some optical losses. The various potential applications of supercontinuum sources include cancer detection, medical imaging, gas sensing, optical coherence tomography, wavelength-division multiplexing, spectroscopy, and metrology. In this thesis, some sincere efforts have been made to numerically design the dispersion engineered photonic crystal fiber designs for supercontinuum generation in the visible, near, and mid-infrared wavelength regions. The computational analysis of the proposed fiber designs is based on the finite element method. We have tried to optimize the dispersion characteristics to reduce the effect of dispersion at the pump wavelength by tweaking the respective geometrical parameters of the core and cladding and also by changing the material composition in the core region. We have numerically analyzed the influence of input peak power, pulse width, peak power, and coherence on the supercontinuum broadening. The proposed silica-based photonic crystal fibers can generate the broad supercontinuum spectrum of bandwidth 0.67 µm to 2.4 µm in the visible and the near-infrared wavelength region at low input power in shorter fiber length. Some newly reported chalcogenide glasses V have been numerically investigated for the ultra-broadband supercontinuum generation in the infrared wavelength region. We have attained the supercontinuum spanning, 1 µm to 14 µm and 2 µm to 11 µm in photonic crystal fibers composed of Ga-Sb-S and GAP-Se chalcogenides respectively. In a tellurite based photonic crystal fiber, we achieved a broadband supercontinuum ranging, 1 µm to 5.5 µm. We have also proposed a photonic crystal fiber based on liquid infiltration to increase the nonlinearity in silica fibers and able to produce highly coherent supercontinuum broadband of spanning, 1 µm to 2.6 µm in the near-infrared wavelength region by using a few centimeters fiber length with low peak power.

碩士
國立交通大學
顯示科技研究所
102
The transmission bandwidth is increasing rapidly in different short-reach networks, such as in data-center networks or transmission among different consumer electronic products. Due to issues of high transmission loss, electromagnetic interference, and limited bandwidth-distance product of the present copper-based electrical cables, they may not provide the bandwidth required for future high-capacity applications. Hence, optical fiber particularly for short-reach applications is desired. In this thesis, we proposed two solutions for optical fiber used in the short-reach networks. The first solution, we developed a 80μm large-core multimode fiber which contains GGP(Glass–Glass–Polymer) and Double Clading technology. Hence, its mechanical strength, properties of low bending loss and coupling properties have enhanced. Another solution, we proposed a square core single mode fiber. It has lower bending loss properties than standard single mode fiber and longer transmission distance compare with multimode fiber. Hopefully it can improve data capacity. We experimentally demonstrated two types of fiber which can achieve error-free in 10 Gb/s data rate and short-distance transmission.