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In response to the development of a next-generation networking (NGN), generalized multi-protocol label switching (GMPLS) technology is required for automatically switched optical network (ASON). Reconfigurable optical add-drop multiplexer (ROADM) is an indispensable device for the ASON, and the dense wavelength division multiplexed (DWDM) signals can be transmitted through the network under the management of the network administrator to configure dynamic customer needs and the desired quality of service (QoS). The ROADM can also increase the efficiency of utilizing the existing capacity of the optical fiber lines and can reduce or waive to set up additional optical fiber lines. This thesis studies a ROADM based on the arrayed waveguide grating (AWG) and the fiber Bragg grating (FBG) to overcome the issue that the current ROADM cannot process input signal channels that is greater than the wavelength channels of the AWG. All kinds of ROADM have been proposed and realized through different optical devices. Among these, hybrid optical circulator and FBG based ROADM is more attractive because of its low crosstalk and polarization insensitivity. However, in the previous study, the structure needs an optical circulator and a fiber Bragg grating per wavelength. If there are 10 wavelengths to be used, you need 10 groups of the optical circulator and the fiber Bragg grating corresponding to each wavelength. This situation not only increases the number of components, but also increases the insertion loss of the system. In this master thesis, we focus on to reduce number of circulators and gratings while obtaining the best results. At the same time we think about whether this structure is the best, and thus try to change the asymmetrical architecture to compare. The final results show that the asymmetrical structure is better, but it does not realize optical cross-connect (OXC). Therefore for the choice, we must choose the best results or the exchangeability of the symmetrical structure.

This thesis mainly focuses on sensor nodes design. A small two-axis and three-axis accelerometer using optic fiber with FBG written in the core as sensing element were originally designed due to the advantages of FBG mentioned above. The proposed design has a concentrated mass sitting in the middle of a rigid frame, and a glass fiber with a FBG written in the fiber core as a stiff spring is connected between each side of the frame and the mass. The two accelerometers can decouple the ground motion along different axes, resulting in virtually zero cross-sensitivity, which exceeds currently available seismometers. The accelerometer or seismometer has a working bandwidth below the structure’s natural frequency and linearly responds to ground movement. COMSOL Multiphysics by using Finite Element Method (FEM) was used to analyze and simulate the two devices.

Steel is widely used as building material for large-scale structures, such as oil and gas pipelines, due to its high strength-to-weight ratio. However, corrosion attack has been long recognized as one of the major reasons of steel pipeline degradation and brings great threat to safety in normal operation of structure. To mitigate the corrosion attacks, coatings are generally applied to protect steel pipelines against corrosion and improve durability of the associated structures for longer service life. Although have higher corrosion resistance, coated pipelines will still get corroded in a long run, as coatings may subject to damages such as cracks. Cracks on coatings could lower the effectiveness of protection for associated structures. Timely updates of up-to-date corrosion rate, corrosion location, and coating conditions to the pipeline risk management model and prompt repairs on these damaged coatings would significantly improve the reliability of protected structures against deterioration and failure. In this study, a corrosion risk analysis system is developed to detect and locate the corrosion induced coating cracks on coated steel using embedded fiber Bragg grating (FBG) sensors. The coatings investigated include high velocity oxygen fuel (HVOF) thermal sprayed Al-Bronze coating, wire arc sprayed Al-Zn coating, and soft coating. Theoretical models of corrosion risk assessment system were carried out followed by systematic laboratory experiments, which shows that the developed system can quantitatively detect corrosion rate, corrosion propagations, and accurately locate the cracks initialized in the coating in real time. This real-time corrosion information can be integrated into pipeline risk management model to optimize the corrosion related risk analysis for resource allocation. To place the sensing units of the system in the most needed locations along the huge pipeline systems for an effective corrosion risk assessment, an example case study is conducted in this study to show how to locate the most critical sensor placement locations along the pipeline using worst case oil and gas discharge analysis. Further applications of the developed system can be integrated with pipeline management system for better maintenance resource allocations. / USDOT-PHMSA

This thesis is concerned with sensitivity alterations of Fiber Bragg Grating (FBG), sensors through additive coatings produced by a combined Laser-Assisted Maskless Micro-deposition (LAMM) and electroless plating process. The coatings can also protect the brittle FBG used in harsh environments. The thesis encompasses design, fabrication procedures, modeling and comparison of experimental and modeling results to gain insight into the advantages and short-comings of the approach. Starting with the opto-mechanical modeling, a program is written in MAPLE to analyze the effect of different on-fiber metallic materials and coating thicknesses on the sensitivity of FBGs to temperature and axial force. On the basis of the proper material and thickness, the sensitivity of FBG at different thermal and loading strains are predicted. The optimal theoretical data suggests that if the thickness of the Ni layer is 30–50 μm, maximum temperature sensitivity is achieved. Some experiments are proposed to test the feasibility of the coated FBG sensors. LAMM is used to coat bare FBGs with a 1-2 μm thick conductive silver layer followed by the electroless nickel plating process to increase layer thickness to a desired level ranging from 1 to 80 μm. Our analytical and experimental results suggest that the temperature sensitivity of the coated FBG with 1 μm Ag and 33 μm Ni is increased almost twice compared to a bare FBG with sensitivity of 0.011±0.001 nm/°C. On the contrary, the force sensitivity is decreased; however, this sensitivity reduction is less than values reported in the literature.

This thesis is concerned with sensitivity alterations of Fiber Bragg Grating (FBG), sensors through additive coatings produced by a combined Laser-Assisted Maskless Micro-deposition (LAMM) and electroless plating process. The coatings can also protect the brittle FBG used in harsh environments. The thesis encompasses design, fabrication procedures, modeling and comparison of experimental and modeling results to gain insight into the advantages and short-comings of the approach. Starting with the opto-mechanical modeling, a program is written in MAPLE to analyze the effect of different on-fiber metallic materials and coating thicknesses on the sensitivity of FBGs to temperature and axial force. On the basis of the proper material and thickness, the sensitivity of FBG at different thermal and loading strains are predicted. The optimal theoretical data suggests that if the thickness of the Ni layer is 30–50 μm, maximum temperature sensitivity is achieved. Some experiments are proposed to test the feasibility of the coated FBG sensors. LAMM is used to coat bare FBGs with a 1-2 μm thick conductive silver layer followed by the electroless nickel plating process to increase layer thickness to a desired level ranging from 1 to 80 μm. Our analytical and experimental results suggest that the temperature sensitivity of the coated FBG with 1 μm Ag and 33 μm Ni is increased almost twice compared to a bare FBG with sensitivity of 0.011±0.001 nm/°C. On the contrary, the force sensitivity is decreased; however, this sensitivity reduction is less than values reported in the literature.

The use of inflatable structures in aerospace applications is becoming increasingly widespread. In order to monitor the inflation status and overall health of these inflatables, an accurate means of shape sensing is required. To this end, we investigated two existing methods for measuring simple curvature, or curvature in one-dimension. The first method utilizes a pair of strain sensing Fiber Bragg Gratings (FBGs) separated by a known distance; dividing the difference in strain by the separation distance yields an experimental value for the one-dimensional curvature at a point. The second method makes use of conductive ink-based flex sensors, which give a variable resistance based on curvature. We used the latter was in a design for a Curvature-Based Inflation Controller (CBIC). While the controller successfully inflated a test body, its overall utility is limited by the simplicity of its sensors. To improve the shape sensing capabilities of the controller, we investigated the use of FBGs in a multidimensional array. We fabricated a curvature-sensing FBG pair on an inflatable membrane and tested its accuracy as the membrane was shaped into a known radius of curvature. This work reports on the assembly of three such curvature-sensing FBG pairs into a two-dimensional Curvature-Sensing Rosette (CSR). The goal is to use this rosette to measure the curvature of a surface in multiple directions at a single point. A 3-D printed surface with saddle geometry was used to calibrate the curvature-sensing rosette. Presented will be methods of extracting values for the tensor of curvature for the surface at a point using the curvature-sensing rosette, along with experimental verification. This essentially defines the local geometry about the rosette, measured in real time. By employing an array of such rosettes across the surface of an inflatable structure, the local curvature of the inflatable could be known at every point. Combining these curvature measurements can yield an accurate depiction of the global geometry. Thus, the inflation status of the inflatable space structure could be monitored in real time.

This dissertation presents contact force sensors that are based on an emerging fibre-optic sensing technology, the in-fibre Bragg grating (FBG), for contact force measurements between cartilage surfaces in the human hip. There are two main motivations for force measurement in hips (and other joints). First, there is clinical evidence that suggests excessive force magnitude and duration can cause painful degeneration of joints. Second, insights from ex vivo force measurements during simulated physiologic loading are the basis of the rationale for corrective surgeries meant to halt degeneration and restore proper joint function by restoring natural joint mechanics. The current standard tools for force measurements in joints are force/stress sensitive films. There are problems associated with inserting these films into joints that affect the force/stress measurements. To insert the films, the joint must be dissected of surrounding soft tissues and, ultimately, the joint must be taken apart (disarticulated). Following disarticulation, films are fixed to cartilage surfaces, and the joint is re-assembled so that physiologic loads can be applied. The negative consequence of dissection and disarticulation is that the natural mechanics of the intact joint are permanently lost and, therefore, film measurements do not indicate the actual joint mechanics. Moreover, covering cartilage surfaces with rigid films alters the natural contact mechanics of the joint. The force sensors presented in this dissertation are designed for local force measurement over the region of the optical fibre containing the FBG and address limitations of force/stress sensitive films. The FBG force sensors are extremely small (major diameters ranging from 0.165 mm to 0.24 mm) and can be inserted into joint spaces without dissection of soft tissues and disarticulation thereby allowing the joint to remain intact. Theoretical and experimental results indicate that FBG sensor measurements are less affected by the mechanical properties of cartilage than are film sensors. The sensors presented in this dissertation also address limitations with previous FBG based force sensors and are the first application of FBGs in intact human hips. The sensors are smaller, and therefore less invasive, and insensitive to orientation, axial strain and temperature, unlike other FBG sensors presented in the literature. / Graduate

[EN] In this thesis we propose the design and characterization of advanced optical de- vices used in coherent direct sequence optical en/decoding, also called temporal phase en/decoding, based on SSFBGs (Super-Structured Fiber Bragg Grating). The aim of this thesis is to enhance the overall performance of the proposed devi- ces used in optical en/decoding and their characteristics, such as: insertion losses and reflectivity, spectral bandwidth, spectral efficiency and chromatic dispersion present in the optical fiber used in the Telecommunication network. To achieve this goal, modifications in the design and fabrication process were pro- posed. Additionally, encoder and decoder integrated devices based on (Silicon On Insu- lator technology), were presented. The design of the integrated devices is based on unit cells, which are composed of directional couplers, delay lines and thermo- optical heaters. The use of thermo-optical structures enables the code to be tuned. The characteristics of the devices, along with the most important related parame- ters were defined accurately for both technologies. Furthermore, a mathematical model was developed for the encoding and decoding process ,and the results of simulations are shown. The experimental encoding and decoding process was carried out using SSFBGS devices, and hybrid experiments were also performed using integrated devices with SSFBGs, demonstrating that all the technologies are completely compatible. Finally, a characterization methodology based on optical single side band was deve- loped in order to achieve complete frequency characterization (modulus and phase) of the optical devices proposed, leading to the recovery of the impulse response. / [ES] En este trabajo se propone el diseño y caracterización de dispositivos ópticos avanzados para aplicaciones de codificación óptica en secuencia directa coherente, también denominada codificación temporal en fase, basados en SSFBGs (Super- Structured Fiber Bragg Grating). El objetivo de la tesis es mejorar el comportamiento general de los dispositivos propuestos para la codificación óptica y el de sus características, como lo son: pér- didas de inserción y reflectividad, ancho de banda de los dispositivos, eficiencia espectral y finalmente el comportamiento frente a la dispersión cromática presente en la fibra óptica utilizada en la red de telecomunicaciones. Para alcanzar dicho objetivo se proponen modificaciones en el proceso de diseño y fabricación de los dispositivos basados en fibra. Adicionalmente, se presenta la implementación de estos dispositivos codificadores y decodificadores en tecnología integrada basada en silicio (SOI, Silicon on Insu- lator), cuyo diseño está basado en celdas unitarias compuestas por acopladores direccionales, líneas de retardo y desfasadores termo-ópticos, que permite la sin- tonización de los códigos. Para ambas tecnologías se definen con precisión los dispositivos necesarios y sus parámetros más importantes, se desarrolla el modelo teórico matemático y se mues- tran los resultados de simulación del proceso de codificación y decodificación. Diferentes montajes experimentales son llevados a cabo para verificar el proceso de codificación y decodificación para los dispositivos en fibra; así como la verificación conjunta de dispositivos integrados y SSFBGs, presentando la total compatibili- dad entre las tecnologías. Para finalizar, se desarrolla una metodología basada en la modulación en banda lateral única, para la caracterización frecuencial completa (módulo y fase) de los dispositivos bajo estudio, permitiendo la recuperaicón de su respuesta impulsiva. / [CAT] En aquest treball es proposa el disseny i caracterització de dispositius òptics ava- nçats basats en SSFBGs (Super-Structured Fiber Bragg Grating) per a aplicacions de codificació òptica en seq üència directa coherent, també anomenada codificació temporal en fase. L'objectiu de la tesi és millorar el comportament general dels dispositius propo- sats per a la codificació òptica i les seves característiques com pèrdues d'inserció i reflectivitat, amplada de banda dels dispositius, eficiència espectral i finalment el comportament davant la dispersió cromàtica present en la fibra òptica utilitzada en la xarxa de telecomunicacions. Per assolir aquest objectiu es proposen modificacions en el procés de disseny i fa- bricació dels dispositius basats en fibra. Addicionalment, es presenta la implementació d'aquests dispositius codificadors i descodificadors en tecnologia integrada basada en silici (SOI, Silicon on Insulator). El disseny està basat en celáles unitàries compostes per acobladors direccionals, lí- nies de retard i desfasadors termo-òptics, que permeten la sintonització dels codis. Per a ambdues tecnologies es defineixen amb precisió els dispositius necessaris i els seus paràmetres més importants. També es desenvolupa el model teòric matemàtic i es mostren els resultats de simulació del procés de codificació i descodificació. Així mateix, per a verificar el procés de codificació i descodificació dels disposi- tius en fibra, a més de la verificació conjunta de dispositius integrats i SSFBGs, s'utilitzen diferents muntatges experimentals. Així doncs es presenta la total com- patibilitat entre les tecnologies. Per finalitzar, es desenvolupa una metodologia basada en la modulació en banda lateral única per a la caracterització freqüencial completa (mòdul i fase) dels dis- positius baix estudi. D'aquesta manera es permet la recuperació de la seva resposta a l'impuls. / Baños López, R. (2015). Diseño y caracterización de dispositivos codificadores y decodificadores para sistemas OCDMA Coherentes [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/52022 / TESIS

Sensors have become essential elements in human life for safe and comfortable existence in the ever demanding world. Various technologies over decades have contributed in their own way fulfilling innumerable sensing requirements. The discovery of optical sensor technologies has revolutionized the sensing field due to their inherent advantages. Among the large number of fiber optic sensor technologies, FBG based sensors have become widely known and popular within and outside the photonics community and has seen a prominent rise in their utilization. This thesis explores the use of FBG sensors for a wide range of applications scanning across a variety of engineering and medical applications, in the areas of civil engineering, biomechanical engineering, aerospace engineering, geoengineering, etc. It also deals with newer methods of packaging FBG sensors for the measurement of specific engineering parameters like strain, temperature, pressure, displacement and vibration. In the field of civil engineering, FBG sensors are employed for strain sensing on a prism and furthermore tested on a full size brick wallet. During this study, emphasis is made on substituting traditional sensors by specially packaged FBG sensors with the intent of either enhancing the sensing system’s performance or in merging/uniting the inherent advantages of FBG sensors. In the area of biomechanics, a novel sensor methodology using FBG sensors, for measuring surface strains generated on the skin of the calf muscle during various leg exercises is proposed. This methodology is used to address one of the most critical and life threatening issues in long distance air travel, namely the Deep Vein Thrombosis. Further, a FBG sensor based plantar sensing plate, is designed and developed, to measure plantar strain distribution in foot and also to analyze the postural stability. In the field of aerospace engineering, FBG sensors are used for addressing two of the most vital issues; Structural Health Monitoring (SHM) and direct measurement of pressure and temperature on the surface of an aircraft under hypersonic wind flow. Carbon Fiber Composite coupon level testing is carried out to obtain a generic strain calibration factor for the FBG sensor. Further, FBG sensors are exploited for the direct measurement of absolute temperature and pressure on the leeward surface of blunt cone at hypersonic wind speeds. In the domain of geoengineering, the feasibility studies have been undertaken to use a FBG as a seismic sensor and as a bore-well characterizing sensor. A novel FBG seismic sensor package is developed using a single FBG sensor to pick up the seismic waves propagating through the ground generated from earthquakes and ground tremors. Further, FBG sensors are used for measurement of temperature profiles in a bore-well to delineate and characterize the behavior of fractures during seasonal climatic changes. To summarize, the present thesis demonstrates a comprehensive experimental study which bring out the utility of FBG sensors in a variety of challenging applications.