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Trifurcated optical fiber displacement sensors (OFDSs) are increasingly used in industrial and aerospace applications. The critical element of the sensor is the fiber bundle. However, there is no straightforward method to calculate it from the working specifications of the sensor, the number of fibers needed, their size, and arrangement. This work presents a simple yet accurate method to design trifurcated OFDSs. The proposed method allows to derive the geometrical arrangement and size of the fibers from three simple equations, thus reducing significantly the difficulty and complexity of the OFDS design. Those three equations depend on the working point, working range, required sensitivity, and maximum size of the bundle. In this way, the proposed method will save valuable time for researchers and engineers who wish to design, fabricate, and use this type of OFDSs. The procedure is explained in detail with two examples. The results predicted by the model are compared with the experimental results of a bundle with identical fiber arrangement and dimensions. The results show good agreement with a deviation of less than 1% in the working range of the sensor.

Here, it is proposed an alternative to magnify the sensitivity of a single optical fiber interferometric sensor up to two orders of magnitude. The method consists of fabricating the sensing interferometer with a specific length whose spectrum is added to that of a virtual interferometer whose length is linked to the sensing interferometer. In this manner, the spectrum of the sensing and virtual interferometers are made to coincide in a maximum or a minimum. The pattern resulting from said sum has a well-defined envelope that is easy to monitor and correlate with the measurand. Thus, the sensor sensitivity can be magnified as desirable. To demonstrate the method, a microscopic Fabry-Perot interferometer was fabricated and tested as temperature sensor. A temperature sensitivity amplification of 124 times was demonstrated experimentally. The method here proposed may pave the way to practical implementation of the Vernier effect with a single interferometer or resonator.

90 p., Los sensores basados en fibra óptica han alcanzado una madurez en entornos industriales gracias a su mayor versatilidad y rendimiento frente a los sensores tradicionales, por lo que se han convertido en una alternativa viable y prometedora. Estos sensores tienen aplicaciones en sectores tan diversos como la salud, telecomunicaciones, seguridad, espaciales, aeronáuticas, entre otras, por lo tanto, los sensores de fibra óptica se han vuelto prácticamente indispensables para todas las ramas de la industria. De hecho, no hay área industrial que pueda prescindir de la medición, las pruebas, la supervisión o la automatización.En esta tesis se presenta como un compendio de artículos publicados. Su estructura consta de una primera sección de síntesis que incluye una introducción al tema de la investigación, la descripción del marco teórico y las herramientas metodológicas utilizadas para tal fin, la definición de la hipótesis y los objetivos que se persiguen. Así mismo un resumen y discusión de los resultados. En la segunda sección se presentan las conclusiones de la investigación realizada durante la tesis, así como las futuras líneas deinvestigación. Por último, en la tercera sección, se mencionan las contribuciones durante la tesis que incluyen una patente europea, trabajos presentados en congresos internacionales, tres artículos publicadosen revistas especializadas. Esto es lo que ha permitido presentar esta tesis como un compendio de artículos. La investigación descrita en esta tesis se divide en dos líneas, en ambas se explican en detalle el diseño, fabricación y prueba de cada sensor. En la primera, se explica el desarrollo de un sensor de índice de refracción con un gran rango de medición e independencia a la temperatura basado en un interferómetro Fabry Perot. Dicha investigación y sus resultados han dado lugar a una patente europea y a un artículo científico que se incluyen en el Artículo 1. En la segunda parte se describen dos sensores basados en fibras multi-núc

This paper employs the solution-doping technique for the fabrication of polymer optical fibers (POFs) doped with two perylene derivatives, Lumogen Yellow 083 and Lumogen Red 305, in different combinations. With the solution-doping technique is very easy to control the amount of dopant penetration into the core of non-doped uncladded fibers, allowing the fabrication of active POFs with a novel ring-doped structure. In addition to manufacturing the fibers, these have also been optically characterized. Specifically, the influence of the combination of dopants, pumping power and wavelength, as well as the light propagation distance, have been measured and analyzed. Furthermore, time-resolved emission characteristics have also been measured to determine the fluorescence lifetimes and to extract information about the energy transfer between the dopants. Finally, the aim of this work has been to investigate the performance of the aforementioned POFs for fluorescent lighting applications, with a special focus on tunable light sources, and also for sensing applications.

Graphene, a two-dimensional hexagonal honeycomb carbon structure, is widely used in membrane technologies thanks to its unique optical, electrical, mechanical, thermal, chemical and photoelectric properties. The light weight, mechanical strength, anti-bacterial effect, and pollution-adsorption properties of graphene membranes are valuable in water treatment studies. Incorporation of nanoparticles like carbon nanotubes (CNTs) and metal oxide into the graphene filtering nanocomposite membrane structure can provide an improved photocatalysis process in a water treatment system. With the rapid development of graphene nanocomposites and graphene nanocomposite membrane-based acoustically supported filtering systems, including CNTs and visible-light active metal oxide photocatalyst, it is necessary to develop the researches of sustainable and environmentally friendly applications that can lead to new and groundbreaking water treatment systems. In this review, characteristic properties of graphene and graphene nanocomposites are examined, various methods for the synthesis and dispersion processes of graphene, CNTs, metal oxide and polymer nanocomposites and membrane fabrication and characterization techniques are discussed in details with using literature reports and our laboratory experimental results. Recent membrane developments in water treatment applications and graphene-based membranes are reviewed, and the current challenges and future prospects of membrane technology are discussed.

En este trabajo de fin de máster, se han analizado y obtenido franjas de interferencia producidas por un interferómetro estelar de Fizeau, utilizando como fuente estelar un LED de banda ancha conectado a una fibra óptica de plástico y siete filtros astronómicos de diferente longitud de onda y anchura espectral. Se han desarrollado las bases teóricas y aproximaciones necesarias para la discusión de los resultados experimentales, siendo la coherencia temporal y espacial de la luz fundamentales para su compresión. Las distribuciones de intensidad detectadas con diferentes líneas base y longitud de onda han sido descritas satisfactoriamente bajo la aproximación de luz “quasi-monocromatica”. Las variaciones con la línea base y la longitud de onda de la visibilidad, utilizando la aproximación “equal-time”, han permitido determinar el tamaño de la fuente estelar con un error menor que un 25 %.

[EN] In this paper, we report on a multicore fiber-based (MCF) temperature sensor that operates in a wide thermal range and that is robustly packaged to withstand harsh environments. To develop the sensor, the fundamentals concerning the effect of temperature on such fibers have been analyzed in detail to predict the most temperature sensitive MCF geometry. Thanks to it, the device, which operates in reflection mode and consists of a short segment of strongly coupled MCF fusion spliced to a standard single mode fiber, shows higher sensitivity than other devices with identical configuration. Regarding its packaging, it consists of an inner ceramic and two outer metallic tubes to provide rigidity and protection against impacts or dirt. The device was calibrated for a thermal range from -25 degrees C to 900 degrees C and a K-type thermocouple was used as reference. Our results suggest that the manufactured optical thermometer is as accurate as the electronic one, reaching a sensitivity up to 29.426 pm/degrees C with the advantage of being passive, compact and easy to fabricate and interrogate. Therefore, we believe this device is appealing for industrial applications that require highly sensitive temperature sensing in very demanding environments, and that the analysis included in this work could be analogously applied to develop sensitivity-optimized devices for other parameters of interest.

[EN] Sensors based on Bragg gratings inscribed in conventional single mode fibers are expensive due to the need of a sophisticated, but low-speed, interrogation system. As an alternative to overcome this issue, in this work, it is proposed and demonstrated the use of coupled-core optical fiber Bragg gratings. It was found that the relative reflectivity from such gratings changed when the coupled-core fiber was subjected to point or periodic bending. This feature makes the interrogation of such gratings simple, fast, and cost-effective. The reflectivity changes of the gratings are attributed to the properties of the supermodes supported by the coupled-core fiber. As potential applications of the referred gratings, intensity-modulated vector bending and vibration sensing are demonstrated. We believe that the results reported here can pave the way to the development of many inexpensive sensors. Besides, coupled-core fiber Bragg gratings may expand the use of grating technology in other areas.

[EN] Optical fiber-based Localized Surface Plasmon Resonance (OF-LSPR) biosensors have emerged as an ultra-sensitive miniaturized tool for a great variety of applications. Their fabrication by the chemical immobilization of gold nanoparticles (AuNPs) on the optic fiber end face is a simple and versatile method. However, it can render poor reproducibility given the number of parameters that influence the binding of the AuNPs. In order to develop a method to obtain OF-LSPR sensors with high reproducibility, we studied the effect that factors such as temperature, AuNPs concentration, fiber core size and time of immersion had on the number and aggregation of AuNPs on the surface of the fibers and their resonance signal. Our method consisted in controlling the deposition of a determined AuNPs density on the tip of the fiber by measuring its LSPR signal (or plasmonic signal, Sp) in real-time. Sensors created thus were used to measure changes in the refractive index of their surroundings and the results showed that, as the number of AuNPs on the probes increased, the changes in the Sp maximum values were ever lower but the wavelength shifts were higher. These results highlighted the relevance of controlling the relationship between the sensor composition and its performance.

In this paper, we report the temperature effects on the luminescence of polymer optical fibers doped with Lumogen dyes (red and orange). Specifically, we have analyzed the intensity and the average wavelength of the spectra emitted by both fibers when they are heated from 30 degrees C to 90 degrees C. An almost full self-recovery of the signal in the fiber doped with Lumogen red has been observed when the fiber is subjected to thermal cycles with oscillating temperature variations between 30 degrees C and 90 degrees C. The emitted spectra are red/blue shifted when the fiber sample is heated/cooled with a final temperature sensitivity around 0.07 nm/degrees C when a stationary situation is reached.

An optical gauge based on coupled multi-core fiber is proposed and experimentally demonstrated. By using direct laser writing to selectively break the fiber index profile symmetry, asymmetric mode coupling between cores is introduced. This allows to fabricate optical gauges with the ability to detect and differentiate different types of deformation in structures using just a single sensor. The fabricated optical gauges are compared with calibrated commercial gauges and fiber Bragg gratings as strain, vibration and curvature gauge. The tests indicate superior performance of this novel optical gauge over the commercially available sensors and offer the highest sensitivities. The proposed technology could be key to the fabrication of new fiber-based sensing devices with more capabilities and better features than previously achieved.

In this work, we report on a twin-core fiber sensor system that provides improved spectral efficiency, allows for multiplexing and gives low level of crosstalk. Pieces of the referred strongly coupled multicore fiber are used as sensors in a laser cavity incorporating a pulsed semiconductor optical amplifier (SOA). Each sensor has its unique cavity length and can be addressed individually by electrically matching the periodic gating of the SOA to the sensor's cavity roundtrip time. The interrogator acts as a laser and provides a narrow spectrum with high signal-to-noise ratio. Furthermore, it allows distinguishing the response of individual sensors even in the case of overlapping spectra. Potentially, the number of interrogated sensors can be increased significantly, which is an appealing feature for multipoint sensing.

We derive a general solution based on geometric optics that describes the light propagation properties in multimode optical fibers with inverted refractive index profiles. Using this general solution, we classify rays according to their propagation properties and calculate the analytical expressions of the ray trajectories inside these fibers under different launching conditions. In addition, we discuss the most suitable propagation conditions that maximize the confinement of light power in the vicinity of the core-cladding interface for sensing purposes.

[EN]In general, a sensor is used to monitor a single parameter only, and in many cases, a reference sensor is necessary to compensate the effect of temperature. Here, we demonstrate that a single supermode interferometer is capable of monitoring two parameters simultaneously. Said interferometer was fabricated with a segment of strongly coupled multicore fiber fusion spliced at the end of a standard single mode fiber. The free end of the multicore fiber was flat, thus, it behaved as a low reflectivity mirror whose reflection depended on the external refractive index. The reflection spectrum of our supermode interferometer consisted of well-defined periodic maxima and minima whose values and position varied when the interferometer was exposed to refractive index and temperature changes. In the Fourier domain, the changes of the interference pattern can be decoded easily. We demonstrate that the supermode interferometer here proposed can be useful to measure the thermo-optic coefficient of a sample. An important advantage of the device reported here is that the length of the multicore fiber is not determinant on the performance of the sensor. In addition, the device can be reused multiple times.

In this paper we report on the theoretical analysis and fabrication of a dual-core microstructured polymer optical fiber (mPOF) and demonstrate how the coupling characteristics of a dual-core mPOF may be a key factor to assess the quality of the fabrication process. The coupling characteristics of this fiber have been tested and, for comparison purposes, simulations regarding the effects of inaccuracies during the manufacturing process were carried out to evaluate the fabrication quality. Results indicate that theoretical, simulation and experimental data are in good agreement, which highlights the uniformity of the microstructure along the fiber and the quality of its fabrication process. In fact, the manufactured mPOF reached a coupling efficiency up to 95.26%, which makes this mPOF appealing for applications in which highly efficient power couplers are required.

We report on recent advances in the use of inexpensive polymer optical fibres (POFs) for sensing applications in avionics. The sensors analysed in this manuscript take advantage of the unique properties of polymers, such as high flexibility, elasticity, and sensitivity, and they range from strain, elongation, and vibration interrogators to level and temperature meters, leading to cost-effective techniques for structural health monitoring in aircraft structures. We also highlight recent power-supply methods using Power-over-POF in order to feed sensors remotely, and we discuss the constraints imposed by connectors on the performance of POF networks in aircrafts.

169 p., Hoy en día, gracias al uso de fibras ópticas, el desarrollo de sensores bioquímicos económicos y de altas prestaciones capaces de realizar medidas en tiempo real es posible, modificando esta tecnología por la tradicional basada en equipamientos caros, grandes y complejos. Por esta razón, en esta tesis hemos desarrollado un sensor mediante nanopartículas de oro inmovilizadas en la cara de una fibra óptica. El sensor que proponemos combina las ventajas de las fibras ópticas con el efecto plasmón de las nanopartículas, que proporcionan gran sensibilidad a cambios en el medio externo. Sin embargo, la mayor novedad que esta tesis proporciona es el uso de la nano-espectroscopia. Esta técnica se basa en hacer coincidir las frecuencias de resonancia de las nanopartículas con el elemento bioquímico que se quiera detectar, consiguiendo altos niveles de selectividad y sensibilidad, en contraposición con los métodos convencionales que se basan en medir cambios en longitud de onda de la frecuencia de resonancia de las nanopartículas. Para demostrar la validez de la nano-espectroscopia en la punta de una fibra óptica, se han realizado medidas para detectar iones de cobre (II) y Citocromo c, consiguiendo unos límites de detección varios órdenes de magnitud por debajo de los sensores basados en nano-espectroscopia mediante microscopios. Además, esta tesis contribuye también a un mayor entendimientodel proceso de inmovilización de las nanopartículas en la fibra óptica gracias a la amplia caracterizaciónque se ha realizado.

We propose and demonstrate a compact and simple vector bending sensor capable of distinguishing any direction and amplitude with high accuracy. The sensor consists of a short segment of asymmetric multicore fiber (MCF) fusion spliced to a standard single mode fiber. The reflection spectrum of such a structure shifts and shrinks in specific manners depending on the direction in which the MCF is bent. By monitoring simultaneously wavelength shift and light power variations, the amplitude and bend direction of the MCF can be unmistakably measured in any orientation, from 0 degrees to 360 degrees. The bending sensor proposed here is highly sensitive even for small bending angles (below 1 degrees).

Fibre bundle-based reflective optical sensors are good candidates for parameter monitorisation in aero engines. Tip clearance is one of those parameters of great concern that is necessary to monitor. Within this optical technology, the evolution experienced by a custom-designed optical sensor is presented from its first configuration up to the fifth one. The performance of the last configuration is compared with those of other two optical sensors that are also based on a fibre bundle design. The comparison has been carried out in an experimental program in a transonic wind tunnel for aero engines. The proven high resolution and sensitivity of the last configuration of the optical sensor opens up the possibility to detect blade defects, cracks, etc. that could otherwise be hard to track.

We report on a compact, highly sensitive all-fiber accelerometer suitable for low frequency and low amplitude vibration sensing. The sensing elements in the device are two short segments of strongly coupled asymmetric multicore fiber (MCF) fusion spliced at 180 degrees with respect to each other. Such segments of MCF are sandwiched between standard single mode fibers. The reflection spectrum of the device exhibits a narrow spectrum whose height and position in wavelength changes when it is subjected to vibrations. The interrogation of the accelerometer was carried out by a spectrometer and a photodetector to measure simultaneously wavelength shift and light power variations. The device was subjected to a wide range of vibration frequencies, from 1 mHz to 30 Hz, and accelerations from 0.76 mg to 29.64 mg, and performed linearly, with a sensitivity of 2.213 nW/mg. Therefore, we believe the accelerometer reported here may represent an alternative to existing electronic and optical accelerometers, especially for low frequency and amplitude vibrations, thanks to its compactness, simplicity, cost-effectiveness, implementation easiness and high sensitivity.

The present work deals with a curvature sensor that consists of two segments of asymmetric multicore fiber (MCF) fusion spliced with standard single mode fiber (SMF). The MCF comprises three strongly coupled cores; one of such cores is at the geometrical center of the MCF. The two segments of MCF are short, have different lengths (less than 2 cm each), and are rotated 180 degrees with respect to each other. The fabrication of the sensor was carried out with a fusion splicing machine that has the means for rotating optical fibers. It is demonstrated that the sensor behaves as two SMF-MCF-SMF structures in series, and consequently, it has enhanced sensitivity. The device proposed here can be used to sense the direction and amplitude of curvature by monitoring either wavelength shifts or intensity changes. In the latter case, high curvature sensitivity was observed. The device can also be used for the development of other highly sensitive sensors to monitor, for example, vibrations, force, pressure, or any other parameter that induces periodic or local curvature or bending to the MCF segments.

The facet of optical fibers coated with nanostructures enable the development of ultraminiature and sensitive (bio)chemical sensors. The reported sensors until now lack of specificity and the fabrication methods offer poor reproducibility. Here, we demonstrate that by transforming the facet of conventional multimode optical fibers onto plasmon resonance energy transfer (PRET) antenna surfaces the specificity issues may be overcome. To do so, a low cost chemical approach was developed to immobilize gold nanoparticles on the optical fiber facet in a reproducible and controlled manner. Our nanosensors are highly selective as PRET is a nanospectroscopic effect that only occurs when the resonant wavelength of the nanoparticles matches that of the target parameter. As an example, we demonstrate the selective detection of picomolar concentrations of copper ions in water. Our sensor is 1,000 times more sensitive than state of the art technologies. An additional advantage of our nanosensors is their simple interrogation; it comprises of a low-power light emitting diode, a multimode optical fiber coupler, and a miniature spectrometer. We believe that the PRET-based fiber optic platform reported here may pave the way of the development of a new generation of ultra-miniature, portable, and hypersensitive and selective (bio)chemical sensors.

En este trabajo se ha estudiado la viabilidad de los concentradores solares de fibras luminiscentes para utilizarlos en entornos espaciales. Para ello se han realizado una serie de experimentos con fibras ópticas de polímero dopadas con diferentes materiales luminiscentes, concentraciones y métodos de fabricación para determinar la fotoestabilidad de la señal emitida por las fibras. Por una parte, se ha analizado la variación de la intensidad durante periodos largos de tiempo y ciclos de iluminación/oscuridad utilizando un simulador solar calibrado (AM1.5G) y por otra, se ha medido la fotoestabilidad de las fibras en función de la temperatura utilizando un horno, y en varios ciclos térmicos. Se ha concluido que las fibras dopadas con el colorante orgánico lumogen red son estables en periodos largos de exposición a la radiación solar (decaimiento menor del 6%) y que las fibras estudiadas son estables con un decaimiento menor del 20% en ciclos térmicos de hasta 90 ºC., In this work, the viability of fiber luminiscent solar concentrators for use in space environment has been studied. To this end, some experiments have been carried out with polymer optical fibers doped with different luminiscent materials, concentrations and manufacturing methods to determine the photostability of the signal emitted by the fibers. On the one hand, the variation of intensity over long periods of time and lighting/dark cycles has been analyzed using a calibrated solar simulator (AM1.5G) and, on the other, the photostability of the fibers has been measured as a function of temperature using an oven, and in several thermal cycles. It has been concluded that the fibers doped with the organic dye lumogen red are stable in long periods of exposure to solar radiation (decay less than 6%) and that the fibers studied are stable with a decay less than 20% in thermal cycles of up to 90 ° C., Lan honetan, zuntz luminiszenteekin egindako eguzki-kontzentragailuen bideragarritasuna aztertu da espazioko inguruneetan erabili ahal izateko. Horretarako, zenbait saiakuntza egin dira material luminiszente, kontzentrazio eta fabrikazio-metodo desberdinekin dopatutako zuntz optikorekin, zuntzek igorritako seinalearen fotoegonkortasuna zehazteko. Alde batetik, denbora-tarte luzeetan eta argiztapen/iluntasun-zikloetan intentsitatearen aldaketa aztertu da, kalibratutako eguzki-simulagailu bat (AM1.5G) erabiliz, eta, bestetik, labe bat erabiliz, zuntzen fotoegonkortasuna neurtu da tenperaturaren arabera eta zenbait ziklo termikotan. Ondorioztatu da, lumogen red koloratzaile organikoarekin dopatutako zuntzak egonkorrak direla eguzki-erradiazioko esposizio-aldi luzeetan (beheraldia % 6a baino gutxiago) eta aztertutako zuntzak egonkorrak direla 90 ºC-rainoko ziklo termikoetan, beraien intentsitatea % 20 baino gutxiago jaitsiz.

In this work, we propose an interferometric humidity sensor based on a polymer micro-cap bonded off-center on the polished end of a standard single mode fiber (SMF). In our sensor, the sensitive part is the micro-cap. In the interferometer fabrication process, we can adjust the misalignment between the core and the micro-cap. It allowed us to control the visibility of the interference pattern. In our device, water molecules absorbed by the polymer microcap causes changes in the height of the microcap. This results in measurable shifts of the interference pattern. The fabricated samples were tested in a calibrated climatic chamber in the range from (similar to)10 to (similar to)95% of relative humidity (RH). The sensitivity and resolution of our device was found to be 148 pm per %RH and 0.04% RH, respectively. The obtained results suggest that our sensors can be useful to monitor relative humidity (RH) in miniature spaces.

The performance of a precisely controlled drilling technique is critical in the fabrication process of microstructured polymer optical fibres. For the creation of a holey preform, adequate drilling bits with large length-to-diameter ratios provide the ability of machining preforms with complex structures and large lengths in a relatively short time. In this work, we analysed different drilling bits and techniques that can be employed for the creation of such preforms, and key parameters characterising the quality of the drilled holes, such as surface rugosity, diameter deviation, coaxiality and cylindricity were measured. For this purpose, based on theoretical simulations, four rings of air holes arranged in a hexagonal pattern were drilled in the preforms with different drill bits, and the experimental results for the above mentioned parameters have been presented. Additionally, optical power distribution of the fabricated microstructured polymer optical fibres was theoretically calculated and experimentally measured

[EN]A small size and compactly packaged optical sensor for high-temperature measurements is reported. The sensor consists of a short piece of multi-core fiber (MCF) spliced to the distal end of a single-mode fiber. The packaging consists of an inner ceramic shield that prevents bending, curvature, and vibration effects on the MCF, and an outer metallic shield that protects the device against impacts. The interaction between specific supermodes excited in the MCF creates an interference pattern that shifts linearly with the temperature. The sensor was calibrated in the range from 200 to 1000 °C and a K-type thermocouple was used as a reference. The average temperature sensitivity was found to be 24.8 pm/°C with a response time of 15 s. Our results indicate that our MCF interferometric thermometer is as accurate as an electronic one with the advantage that it is passive. Therefore, we believe that the proposed sensor is suitable for industrial applications.

205 p., La sociedad actual ha experimentado los mayores y más destacados avances tecnológicos desde la Revolución Industrial a finales del siglo XIX. El desarrollo en ámbitos como el transporte, las comunicaciones, la medicina o la producción de energía, entre otros, se ha convertido en el pilar principal del progreso global actual. En este contexto, esta tesis engloba el uso de fibras ópticas de plástico dopadas en dos áreas en pleno desarrollo y muy demandadas por la sociedad moderna: comunicaciones ópticas (láseres y amplificadores de fibra) y producción de energía sostenible (concentración de luz solar mediante fibras dopadas).

165 p., Esta tesis propone una arquitectura para la medición de dos parámetros que caracterizan elfuncionamiento de un motor aeronáutico: el Tip Clearance y el Time of Arrival. El primero representa ladistancia desde la punta de álabe a la carcasa del motor. El segundo representa el instante en que el álabepasa frente al sensor. Ambos parámetros son el punto de partida para realizar un análisis del estado devibración que sufre ese motor.La arquitectura propuesta para le medida del Tip Clearance y del Time of Arrival consigue podermonitorizar cada álabe de forma individual realizando las medidas en tiempo real. La arquitectura sepuede adaptar a las formas de onda de diversos sensores de los que se emplean habitualmente en estecampo. También permite configurar diversos aspectos de la medida o del ensayo. La arquitectura esescalable y establece un medio de sincronización que permite que se puedan medir simultáneamentevarios sensores instalados en diferentes puntos de la carcasa de motor.La validación de la arquitectura se ha realizado con las formas de onda de un sensor óptico trifurcadoprobado en ensayos reales de una etapa compresora en un túnel de viento. En la implementación se hanpropuesto algoritmos para la determinación de los dos parámetros que se adaptan al procesadoconcurrente y secuencial de una FPGA.

This paper employs the solution-doping technique for the fabrication of active polymer optical fibers (POFs), in which the dopant molecules are directly incorporated into the core of non-doped uncladded fibers. Firstly, we characterize the insertion of a solution of rhodamine B and methanol into the core of the fiber samples at different temperatures, and we show that better optical characteristics, especially in the attenuation coefficient, are achieved at lower temperatures. Moreover, we also analyze the dependence of the emission features of doped fibers on both the propagation distance and the excitation time. Some of these features and the corresponding ones reported in the literature for typical active POFs doped with the same dopant are quantitatively similar among them. This applies to the spectral location of the absorption and the emission bands, the spectral displacement with propagation distance, and the linear attenuation coefficient. The samples prepared in the way described in this work present higher photostability than typical samples reported in the literature, which are prepared in different ways.

A highly sensitive fibre bundle-based reflective optical sensor has been designed and fabricated for Tip Clearance measurements in a turbine rig. The sensor offers high spatial and temporal resolution. The sensor probe consists of a single-mode transmitting fibre and two concentric rings of receiving multimode fibres that collect reflected light in a differential detection gain configuration, yielding a highly linear calibration curve for distance measurements. The clearance measurement range is approximately 2 mm around the central point fixed at 3.2 mm from the probe tip, and the sensitivity of the probe is 61.73 mm(-1). The fibre bundle has been designed to ensure that the distance security specifications required for the experimental program of the turbine are met. The optical sensor has operated under demanding conditions set by the blade and casing design. The experimental results obtained so far are promising and lead us to think that the optical sensor has great potential for online clearance measurements with high precision.

Forster resonance energy transfer (FRET) between two molecules in nanoscale distances is utilized in significant number of applications including biological and chemical applications, monitoring cellular activities, sensors, wireless communications and recently in nanoscale microfluidic radar design denoted by the vibrating FRET (VFRET) exploiting hybrid resonating graphene membrane and FRET design. In this article, a low hardware complexity and novel microfluidic viscosity monitoring system architecture is presented by exploiting VFRET in a novel microfluidic system design. The donor molecules in a microfluidic channel are acoustically vibrated resulting in VFRET in the case of nearby acceptor molecules detected with their periodic optical emission signals. VFRET does not require complicated hardware by directly utilizing molecular interactions detected with the conventional photodetectors. The proposed viscosity measurement system design is theoretically modeled and numerically simulated while the experimental challenges are discussed. It promises point-of-care and environmental monitoring applications including viscosity characterization of blood or polluted water.

We report on microscopic polymer spherical caps bonded onto the cleaved end of a single-mode fiber (SMF) for fast, accurate, and sensitive temperature sensing. The microcaps were fabricated by dispensing sub nano-liter amounts of UV-curable polymer onto the end face of a standard SMF that was cleaved at a small angle. A reflection from the SMF-polymer interface combined with a reflection from the polymer-external medium interface gives rise to a well-defined interference pattern. The high thermal expansion coefficient of the polymer used to build the micro-caps allowed us to achieve temperature sensitivity up to 270 pm/°C, resolution of 0.04 °C, and thermal response time of around 2.5 s. The simple fabrication process and the broad operating wavelength (from 800 to 1600 nm, approximately) of our devices along with the diversity of polymers currently available, make the concept and approach proposed here appealing for diverse sensing applications.

The chromatic dispersion and the refractive index of poly(methyl methacrylate) polymer optical fibers (POFs) have been characterized in this work by using a tunable femtosecond laser and a Streak Camera. The characterization technique is based on the measurement of the time delays of light pulses propagating along POFs at different wavelengths. Polymer fibers of three different lengths made by two manufacturers have been employed for that purpose, and discrepancies lower than 3% have been obtained in all cases.

An experimental investigation on the vibrational behavior of a rotating disk by means of three optical fiber sensors is presented. The disk, which is a scale model of the real disk of an aircraft engine, was assembled in a wind tunnel in order to simulate real operation conditions. The pressure difference between the upstream and downstream sides of the disk causes an airflow that might force the disk to vibrate. To characterize this vibration, a set of parameters was determined by measuring the tip clearance of the disk: the amplitude, the frequency and the number of nodal diameters in the disk. All this information allowed the design of an upgraded prototype of the disk, whose performance was also characterized by the same method. An optical system was employed for the measurements, in combination with a strain gauge mounted on the disk surface, which served to confirm the results obtained. The data of the strain gauge coincided closely with those provided by the optical fiber sensors, thus demonstrating the suitability of this innovative technique to evaluate the vibrational behavior of rotating disks.

The presence of microscopic particles in suspension in industrial fluids is often an early warning of latent or imminent failures in the equipment or processes where they are being used. This manuscript describes work undertaken to integrate different photonic principles with a micro- mechanical fluidic structure and an embedded processor to develop a fully autonomous wear debris sensor for in-line monitoring of industrial fluids. Lens-less microscopy, stroboscopic illumination, a CMOS imager and embedded machine vision technologies have been merged to develop a sensor solution that is able to detect and quantify the number and size of micrometric particles suspended in a continuous flow of a fluid. A laboratory test-bench has been arranged for setting up the configuration of the optical components targeting a static oil sample and then a sensor prototype has been developed for migrating the measurement principles to real conditions in terms of operating pressure and flow rate of the oil. Imaging performance is quantified using micro calibrated samples, as well as by measuring real used lubricated oils. Sampling a large fluid volume with a decent 2D spatial resolution, this photonic micro sensor offers a powerful tool at very low cost and compacted size for in-line wear debris monitoring.

Four different dye-doped polymer optical fibers (POFs) have been fabricated following a two-step fabrication process of preform extrusion and fiber drawing, using poly-(methyl methacrylate) (PMMA) as host material and dye derivatives from perylene and naphtalimide as active dopants. The side illumination technique (SIT) has been employed in order to determine some optical properties of the fabricated fibers, such as the side illumination coupling efficiency, optical loss coefficients, and their performance under solar simulator excitation. The aim of this work is to investigate the performance of the manufactured fibers for fluorescent lighting applications, specially targeting on fluorescent fiber based solar concentrators.

Safety and performance of the turbo-engine in an aircraft is directly affected by the health of its blades. In recent years, several improvements to the sensors have taken place to monitor the blades in a non-intrusive way. The parameters that are usually measured are the distance between the blade tip and the casing, and the passing time at a given point. Simultaneously, several techniques have been developed that allow for the inferencefrom those parameters and under certain conditionsof the amplitude and frequency of the blade vibration. These measurements are carried out on engines set on a rig, before being installed in an airplane. In order to incorporate these methods during the regular operation of the engine, signal processing that allows for the monitoring of those parameters at all times should be developed. This article introduces an architecture, based on a trifurcated optic sensor and a hardware processor, that fulfills this need. The proposed architecture is scalable and allows several sensors to be simultaneously monitored at different points around a bladed disk. Furthermore, the results obtained by the electronic system will be compared with the results obtained by the validation of the optic sensor.Safety and performance of the turbo-engine in an aircraft is directly affected by the health of its blades. In recent years, several improvements to the sensors have taken place to monitor the blades in a non-intrusive way. The parameters that are usually measured are the distance between the blade tip and the casing, and the passing time at a given point. Simultaneously, several techniques have been developed that allow for the inferencefrom those parameters and under certain conditionsof the amplitude and frequency of the blade vibration. These measurements are carried out on engines set on a rig, before being installed in an airplane. In order to incorporate these methods during the regular operation of the engine, signal processing that allows for t

We report on the use of a multi-core fibre (MCF) comprising strongly-coupled cores for accurate strain sensing. Our MCF is designed to mode match a standard single mode optical fibre. This allows us to fabricate simple MCF interferometers whose interrogation is carried out with light sources, detectors and fibre components readily available from the optical communications tool box. Our MCF interferometers were used for sensing strain. The sensor calibration was carried out in a high-fidelity aerospace test laboratory. In addition, a packaged MCF interferometer was transferred into field trials to validate its performance under deployment conditions, specifically the sensors were installed in a historical iron bridge. Our results suggest that the MCF strain sensors here proposed are likely to reach the readiness level to compete with other mature sensor technologies, hence to find commercial application. An important advantage of our MCF interferometers is their capability to operate at very high temperatures.

In this work we show an optical fiber evanescent wave absorption probe for glucose detection in different physiological media. High selectivity is achieved by functionalizing the surface of an only-core poly(methyl methacrylate) (PMMA) polymer optical fiber with phenilboronic groups, and enhanced sensitivity by using a U-shaped geometry. Employing a supercontinuum light source and a high-resolution spectrometer, absorption measurements are performed in the broadband visible light spectrum. Experimental results suggest the feasibility of such a fiber probe as a low-cost and selective glucose detector.

In contrast to conventional polymer optical fibres (POFs), single-mode microstructured POFs (SM mPOF) exhibit polarization properties that make them potentially interesting for their use in the design and development of polarimetric fibre optic systems. In spite of the theoretical sixfold symmetry of the microstructure that yields zero linear birefringence, a measurement technique reveals us that the SM mPOF behaves as a linear birefringent system with clearly defined optical axes and characteristics. Regarding externally induced birefringence mechanisms acting upon the SM mPOF, either bend- and pressure-induced retardations or twist-induced light rotation follow the behaviour predicted theoretically. More specifically, bend-induced retardation varies linearly with the inverse square of the bending radius of the fibre, and in the case of asymmetrical lateral stress, pressure-induced retardation varies with the applied force. As to twist-induced rotation, the electric field rotates linearly with the angle through which the fibre is twisted. All cases are highly reproducible phenomena that, if used advantageously, may yield useful mPOF-based polarimetric optical devices not exploited yet.

The emission properties of a graded-index thermoplastic polymer optical fiber and a step-index thermosetting one, both doped with rhodamine 6G, have been studied. The work includes a detailed analysis of the amplified spontaneous emission together with a study of the optical gains and losses of the fibers. The photostability of the emission of both types of fibers has also been investigated. Comparisons between the results of both doped polymer optical fibers are presented and discussed.

779 p., The paradigm of process monitoring has evolved in the last years, driven by a clear need for improving efficiency, quality and safety of processes and products. Sectors as manufacturing, energy, food and beverages, etc. are fostering the adoption of innovative methods for controlling their processes and products, in a non-destructive, in-place, reliable, fast, accurate and cost-efficient manner. Furthermore, the parameters requested by the industry for the quality assessment are evolving from basic magnitudes as pressures, temperatures, humidity, etc. to complete chemical and physical fingerprints of these products and processes. In this situation, techniques based on the UV/VIS/NIR light-matter interaction appear to be optimum candidates to face the request of the industry. Moreover, at this moment, when we are witnessing a technological revolution in the field of optoelectronic components, which are required for setting up these light-based analyzers.However, being able to integrate these optoelectronic components with the rest of subsystems (electronics, optics, mechanics, hydraulics, data processing, etc.) is not straightforward. The development of these multi-domain and heterogeneous sensor products meeting not just technological but also market objectives poses a considerable technical and organizational challenge for any company.In this context, a methodological hybrid and agile integration of photonic components within the rest of subsystems towards a sensor product development is presented as the main outcome of the thesis. The methodology has been validated in several industrial scenarios, being three of them included in this thesis, which covers from hydraulic fluid quality control to real-time monitoring of alcoholic beverage fermentation process.

163 p., Los sensores basados en fibra óptica son cada vez más utilizados en aeronáutica debido a las ventajas que presentan frente a sensores más tradicionales. En esta tesis se presenta el diseño y desarrollo de un sensor de fibra óptica para la medida del tip clearance y del tip timing en motores aeronáuticos. Este sensor está basado en la modulación de la luz reflejada por parte de los álabes de un motor aeronáutico en función de la distancia a la que se encuentran.En el capítulo 1 se realiza una introducción a los sensores de fibra óptica dedicando especial atención a que utilizan la modulación de la intensidad como principio de funcionamiento, y se explican los parámetros que serán objeto de medida por el sensor desarrollado en la presente tesis.En el segundo capítulo se presenta la metodología seguida en el diseño y desarrollo del sensor. Se definen los objetivos y requisitos iniciales que el sensor debe cumplir y los pasos seguidos hasta conseguirlo.En el tercer capítulo se muestran los resultados obtenidos para aplicaciones reales de funcionamiento del sensor diseñado. Se presentan los resultados conseguidos en dos entornos reales de trabajo. Por un lado, el túnel de viento que el Centro de Tecnologías Aeronáuticas posee en sus instalaciones de Zamudio (Vizcaya), y por el otro, el banco de ensayos con el que cuenta el Instituto Tecnológico de las Fuerzas Aéreas polacas en Varsovia (Polonia).Este documento concluye con un capítulo en el que se recogen las conclusiones del trabajo, así como las líneas futuras del mismo. También se enumeran los artículos (incluidos en un apéndice) en los que se basa la tesis, así como las conferencias y otras publicaciones realizadas durante este periodo.

In this article, we report the design of a reflective intensity-modulated optical fiber sensor for blade tip-clearance measurement, and the experimental results for the first stage of a compressor of an aircraft engine operating in real conditions. The tests were performed in a ground test cell, where the engine completed four cycles from idling state to takeoff and back to idling state. During these tests, the rotational speed of the compressor ranged between 7000 and 15,600 rpm. The main component of the sensor is a tetrafurcated bundle of optical fibers, with which the resulting precision of the experimental measurements was 12 mu m for a measurement range from 2 to 4 mm. To get this precision the effect of temperature on the optoelectronic components of the sensor was compensated by calibrating the sensor in a climate chamber. A custom-designed MATLAB program was employed to simulate the behavior of the sensor prior to its manufacture.

El Trabajo de Fin de Master consiste en un programa que simula el funcionamiento de un sensor de fibra óptica y que puede ser utilizado para aplicaciones concretas como detección de impactos, vibraciones o distancias. Para ello, se ha caracterizado el sensor de forma experimental a distintas temperaturas, en función del ángulo de incidencia y en función de la reflectividad del objetivo. Finalmente, se ha llevado a cabo un estudio de la sensibilidad del sensor en función de diferentes procesados de las señales recogidas.

This paper analyzes the peculiarities of light amplification in doped polymer optical fibres (POFs) by using our computational model under diverse conditions. Specifically, the influence of the numerical aperture and of the radial distribution of the dopant in the fibre, on the one hand, and the most convenient temporal width of the pump pulse, on the other hand, are investigated. Analyses are carried out for both step-index and graded-index POFs. The results presented correspond to fibres excited longitudinally with short light pulses of several energies.; Artikulu honetan, gure eredu konputazionalaren bitartez, argi-anplifikazioaren ezaugarriak aztertu dira dopaturiko polimerozko zuntz optikoetan (PZOetan). Hain zuzen ere, zenbakizko irekiduraren eta dopantearen distribuzio erradialaren eraginaz gain, ponpaketaren denborazko pultsu-zabalera egokiena ere ikertu da. Analisi hauek guztiak maila-indize eta indize gradualeko PZOentzat egin dira. Lorturiko emaitzak energia desberdinetako argi-pultsuen bitartez longitudinalki kitzikaturiko zuntz aktiboetan oinarritzen dira.

En este proyecto se presenta un estudio te orico y experimental de la polarizaci on de la luz en mPOFs cuando estas son sometidas a diferentes perturbaciones, para su aplicaci on en sensado optico.

Aircraft structures require periodic and scheduled inspection and maintenance operations due to their special operating conditions and the principles of design employed to develop them. Therefore, structural health monitoring has a great potential to reduce the costs related to these operations. Optical fiber sensors applied to the monitoring of aircraft structures provide some advantages over traditional sensors. Several practical applications for structures and engines we have been working on are reported in this article. Fiber Bragg gratings have been analyzed in detail, because they have proved to constitute the most promising technology in this field, and two different alternatives for strain measurements are also described. With regard to engine condition evaluation, we present some results obtained with a reflected intensity-modulated optical fiber sensor for tip clearance and tip timing measurements in a turbine assembled in a wind tunnel

3rd International Conference on Mathematical Modeling in Physical Sciences (IC-MSQUARE 2014), In this work, we show the resolution of the rate equations in powder random lasers by using the Crank-Nicholson finite difference method. Light propagation in our powders is described by the model of light diffusion. The generalized time-dependent random laser equations describing our system are formed by three differential coupled equations: two diffusion equations for the pump and emitted light and a rate equation for the density of the dopant molecules in the excited state. The system has been solved for two pumping schemes (one-photon and two-photon excitation) and for a wide range of temporal incident pulses (from femtoseconds to nanoseconds).