Fiber optic sensors and self-reference techniques for temperature measurements in different industrial sectors

Mención Internacional en el título de doctorEl objetivo de este trabajo se centra especialmente en el desarrollo de sensores de fibra óptica y técnicas de autoreferencia para la medida de la temperatura en diferentes entornos industriales. El primer objetivo de este trabajo consiste en el diseño y desarrollo de un sensor de fibra óptica de bajo coste para la medida de la temperatura en transformadores de potencia y aplicaciones biomédicas. En estas aplicaciones, el uso de sensores de temperatura tradicionales resulta inadecuado debido a la presencia de fuertes interferencias electromagnéticas que pueden perturbar la lectura de la temperatura. Uno de los requisitos fundamentales para diseñar un sensor de temperatura que pueda usarse en aplicaciones biomédicas es el uso de materiales biocompatibles en su fabricación. En este sentido, una configuración simple que permite cumplir con los requisitos mencionados anteriormente es la modulación por intensidad en fibras poliméricas. Este tipo de sensores basan la lectura de la temperatura en medir las variaciones de potencia óptica en función de los cambios de temperatura que se aplican sobre el sensor. En este contexto, el uso de la tecnología asociada con la fibra óptica de plástico ofrece ventajas competitivas frente a otros materiales, como son: el uso de dispositivos opto-electrónicos de bajo coste, la posibilidad de utilizar conectores de baja precisión, la posibilidad de utilizar multiplexores y demultiplexores de muy bajo coste, entre muchas otras ventajas. A pesar de estas ventajas, los sensores de intensidad necesitan de esquemas de autoreferencia que eviten fluctuaciones de potencia que interfieran en la lectura de la temperatura. Estas fluctuaciones pueden provenir de fluctuaciones de potencia a lo largo del tramo de fibra óptica entre la unidad de control y el sensor, fluctuaciones de la fuente de luz por cambios en la corriente de alimentación, pérdidas de potencia por envejecimiento de la instalación, entre otras causas. El segundo objetivo de este trabajo consiste en promover el estudio y el desarrollo de técnicas de multiplexado y autoreferencia que implementen sensores fabricados en fibra óptica de plástico. Estas topologías deberán de utilizar dispositivos eficientes desde el punto de vista del consumo de potencia para mejorar con ello el balance de potencias del sistema y por tanto, poder utilizar este tipo de esquemas en redes de corto y medio alcance. Para alcanzar este objetivo, en este trabajo se desarrollan técnicas de autoreferencia y multiplexado de bajo coste basadas en multiplexación por longitud de onda vasta (CWDM, Coarse Wavelength Division Multiplexing). Esta técnica se caracteriza por su amplio desarrollo en el campo de telecomunicaciones como estándar para aplicaciones de corto o medio alcance en redes metropolitanas. Los multiplexores y demultiplexores diseñados para esta topología tienen una rejilla de longitudes de onda con una separación entre canales de 20nm. Este espaciado entre canales dificulta la multiplexación de un elevado número de dispositivos o sensores como podría llevarse a cabo si se usaran dispositivos basados en multiplexación por longitud de onda densa (DWDM, Dense Wavelength Division Multiplexing). Pero presentan una clara ventaja competitiva, los esquemas CWDM requieren bajas tolerancias en la fabricación de fuentes de luz, un control menos exhaustivo de la temperatura de la fuente, filtros ópticos de bajo coste y esquemas de diseño menos complejos. Los menores requisitos técnicos de los dispositivos utilizados con esta tecnología hacen que sea una topología interesante para su uso en redes de sensores de bajo coste. El tercer objetivo consiste en desarrollar sensores sin contacto basados en pirometría de dos colores para el sensado de la temperatura en procesos de mecanizado industrial...As a general aim, this work specifically focuses on the development of temperature sensors and self-reference techniques for temperature measurement in different industrial sectors. The first objective of this work is the design and development of a low-cost fiber optic sensor for measuring temperature in power transformers and biomedical applications where the presence of EMI prohibits the use of traditional sensors. Compatibility with the human being is a requirement when the temperature sensors are used in medical applications. Following simple fiber optic configurations, intensity sensors modulate the optical power loss as the temperature changes, thus providing the measurement as an optical intensity modulation signal. Polymer Optical Fiber (POF) technology, with very low-cost components, enables temperature sensing using a low precision connectors and lenses as well as simple multiplexing and demultiplexing devices, especially if compared with glass optical fibers. However, intensity sensors need a self-referencing method to minimize the influences of long-term aging of source and receptor characteristics, as well as undesirable random short-term fluctuations of optical power loss in the fiber link connecting the control unit, where the measurements are taken, to the remote sensing point, where the optical sensor is located. The second objective of this work is to promote, study and develop a multiplexing strategy to implement and scale POF sensor networks using low cost off-the-shelf devices, enhancing the power budget and keeping the self-reference of the measurements. This work focuses on low-cost Coarse WDM (CWDM) technology, where a grid of wavelengths with a 20nm channel spacing for target distance of up to tens of kilometres is specified. CWDM technology have lately been promoted in the field of telecommunication as standard for metro applications with shorter distances, lower network capacity and cost than Dense WDM (DWDM). This topology requires simpler, wider tolerance laser manufacturing, less laser accurate temperature control and reduced design complexity and cost of optical filters. These relaxed requirements make the CWDM technology an interesting approach for building low-cost self-referencing sensors networks. The development of this technology, adapted to the use of POF, can be carried out with the development of fiber Bragg gratings (FBG) in POF, providing an effective and compact strategy for exploiting fiber links for both propagating directions of the light with a single fiber lead. The third objective is to develop a non-contact two-colour fiber-optic pyrometer for temperature measures in the aerospace machining industry, enhancing the location measurement area, reducing the surface emissivity effect and keeping the self-reference of the measurement…The research work of this dissertation has been supported by the following Spanish projects: TEC2009-14718-C03-03 (DEDOS), and TEC2012-37983-C03-02 (CFOOT-TIC) of the Spanish Interministerial Commission of Science and Technology (CICYT); BES-2010-033348, EEBB-I-12-05434 and EEBB-1-13-07511 of the Spanish Ministry of Economy and Competitiveness; PRX12/00007 of Spanish Ministry of Education; P2013/MIT-2790, FACTOTEM-2/2010/00068/001 and S2013/MIT-2790 (SINFOTON-CM) of Autonomous Community of Madrid. Additional financial support was obtained from ICT COST Action TD1001: Novel and Reliable Optical Fiber Sensor Systems for Future Security and Safety Applications (OFSESA) of the European Union.Programa Oficial de Doctorado en Ingeniería Eléctrica, Electrónica y AutomáticaPresidente: Tianxin Yang.- Secretario: Ricardo Vergaz Benito.- Vocal: Kevin Heggart

El problema isostático inverso de Vening Meinesz. Teoría y desarrollo. Aplicación práctica para la determinación de la profundidad de la discontinuidad de Mohorovičić en la Península Ibérica

La discontinuidad de Mohorovičić, más conocida simplemente como “Moho” constituye la superficie de separación entre los materiales rocosos menos densos de la corteza y los materiales rocosos más densos del manto, suponiendo estas capas de densidad constante del orden de 2.67 y 3.27 g/cm3, y es un contorno básico para cualquier estudio geofísico de la corteza terrestre. Los estudios sísmicos y gravimétricos realizados demuestran que la profundidad del Moho es del orden de 30-40 km por debajo de la Península Ibérica y 5-15 km bajo las zonas marinas. Además las distintas técnicas existentes muestran gran correlación en los resultados. Haciendo la suposición de que el campo de gravedad de la Península Ibérica (como le ocurre al 90% de la Tierra) está isostáticamente compensado por la variable profundidad del Moho, suponiendo un contraste de densidad constante entre la corteza y el manto y siguiendo el modelo isostático de Vening Meinesz (1931), se formula el problema isostático inverso para obtener tal profundidad a partir de la anomalía Bouguer de la gravedad calculada gracias a la gravedad observada en la superficie terrestre. La particularidad de este modelo es la compensación isostática regional de la que parte la teoría, que se asemeja a la realidad en mayor medida que otros modelos existentes, como el de Airy-Heiskanen, que ha sido históricamente el más utilizado en trabajos semejantes. Además, su solución está relacionada con el campo de gravedad global para toda la Tierra, por lo que los actuales modelos gravitacionales, la mayoría derivados de observaciones satelitales, deberían ser importantes fuentes de información para nuestra solución. El objetivo de esta tesis es el estudio con detalle de este método, desarrollado por Helmut Moritz en 1990, que desde entonces ha tenido poca evolución y seguidores y que nunca se ha puesto en práctica en la Península Ibérica. Después de tratar su teoría, desarrollo y aspectos computacionales, se está en posición de obtener un modelo digital del Moho para esta zona a fin de poder utilizarse para el estudio de la distribución de masas bajo la superficie terrestre. A partir de los datos del Moho obtenidos por métodos alternativos se hará una comparación. La precisión de ninguno de estos métodos es extremadamente alta (+5 km aproximadamente). No obstante, en aquellas zonas donde exista una discrepancia de datos significaría un área descompensada, con posibles movimientos tectónicos o alto grado de riesgo sísmico, lo que le da a este estudio un valor añadido. ABSTRACT The Mohorovičić discontinuity, simply known as “Moho” constitutes the division between the rocky and less thick materials of the mantle and the heavier ones in the crust, assuming densities of the orders of 2.67 y 3.27 g/cm3 respectively. It is also a basic contour for every geophysical kind of studies about the terrestrial crust. The seismic and previous gravimetric observations done in the study area show that the Moho depth is of the order of 30-40 km beneath the ground and 5-15 km under the ocean basin. Besides, the different techniques show a good correlation in their results. Assuming that the Iberian Peninsula gravity field (as it happens for the 90% of the Earth) is isostatically compensated according to the variable Moho depth, supposing a constant density contrast between crust and mantle, and following the isostatic Vening Meinesz model (1931), the inverse isostatic problem can be formulated from Bouguer gravity anomaly data obtained thanks to the observed gravity at the surface of the Earth. The main difference between this model and other existing ones, such as Airy- Heiskanen’s (pure local compensation and mostly used in these kinds of works) is the approaching to a regional isostatic compensation, much more in accordance with reality. Besides, its solution is related to the global gravity field, and the current gravitational models -mostly satellite derived- should be important data sources in such solution. The aim of this thesis is to study with detail this method, developed by Helmut Moritz in 1990, which hardly ever has it put into practice. Moreover, it has never been used in Iberia. After studying its theory, development and computational aspects, we are able to get a Digital Moho Model of the Iberian Peninsula, in order to study the masses distribution beneath the Earth’s surface. With the depth Moho information obtained from alternative methods, a comparison will be done. Both methods give results with the same order of accuracy, which is not quite high (+ 5 km approximately). Nevertheless, the areas in which a higher difference is observed would mean a disturbance of the compensation, which could show an unbalanced area with possible tectonic movements or potential seismic risk. It will give us an important additive value, which could be used in, at first, non related fields, such as density discrepancies or natural disasters contingency plans

High spatial resolution optical fiber two colour pyrometer with fast response

Among the different temperature measurement techniques providing micrometer resolution none of them provide fast response and easy access to close distances to the target surface in difficult to access areas. Optical fiber pyrometers provide that access but previous works used large optical fibers with numerical apertures limiting the minimum spot size to be measured. In this study, we propose a novel two colour optical fiber pyrometer based on a low diameter and numerical aperture optical fiber, low-noise photodetectors and high-gain transimpedance amplifiers with a high spatial resolution in the micrometre range and fast response. Using standard optical fibers and related devices provides also a low-cost system. The developed pyrometer presents a high spatial resolution of 16 mum for a target surface at 25 mum with a wide temperature range of 300 to 1200°C it being the highest spatial resolution for this kind of temperature systems. Theoretical analysis and measurements for different pyrometer configurations are reported. This study will help further the microthermography applications in machining processes.This work was supported in part by the Spanish Ministry of Science, Innovation and Universities Grant RTI2018-094669-B-C3 and Juan de la Cierva Grant FJCI-2017-31677, in part by the Directorate for Research and Innovation at Madrid region Grants P2018/NMT-4326, Y2018/EMT-4892 and INTECSOLARIS-CMUC3M; and in part by FSE

Audience Attention and Emotion in News Filmed with Drones: A Neuromarketing Research

Emotional journalism is being driven by audiovisual technology such as drones, also known as unmanned aerial vehicles, which have demonstrated their usefulness in transforming objective news into news stories from a new visual perspective, facilitating access to dangerous or difficult places. They also allow for greater immersion by an audience that has become an active participant in the news, and they contribute to the storytelling of communication despite the risk to privacy and security that their misuse might entail. The aim of this research is to determine the differences in attention and intensity of the emotions experienced when viewing two pieces of audiovisual news: One was filmed with the technological support of a drone, and the other was produced in the conventional way. The techniques of eye tracking and galvanic skin response were used in 30 Spanish university students. The results suggest that attention was focused on the most spectacular visual elements, although the images filmed with a drone received a higher concentration of attention from the subjects, and this attention was spread throughout the entire image, which demonstrates that drones enhance the effectiveness of panoramic images with natural landscapes. The greatest emotion generated by viewing the images recorded with drones was statistically significant, but it was limited exclusively to these particular scenes, and not to the entire recording of the news

Monitoring temperature on machining processes is enhanced using optical fibers

An IR fiber-optic pyrometer measures temperatures above 250 C close to rotating components where other sensing techniques are unsuitableThis work has been sponsored by the Spanish Ministry of Economy and Competitiveness under grant TEC2012-37983-C03-02.Publicad

Optical Fiber Pyrometer Designs for Temperature Measurements Depending on Object Size

The modelling of temperature measurements using optical fiber pyrometers for different hot object sizes with new generalized integration limits is presented. The closed equations for the calculus of the radiated power that is coupled to the optical fiber for two specific scenarios are proposed. Accurate predictions of critical distance for avoiding errors in the optical fiber end location depending on fiber types and object sizes for guiding good designs are reported. A detailed model for estimating errors depending on target size and distance is provided. Two-color fiber pyrometers as a general solution are also discussed

Polymer Optical Fiber Temperature Sensor With Dual-Wavelength Compensation of Power Fluctuations

The design and development of a plastic optical fiber macrobend temperature sensor is presented. The sensor can operate in a temperature range from -55 to 70 degrees C and has a linear response versus temperature with a sensitivity of 8.95.10(-4) degrees C-1. The sensor system uses the ratio of transmittance at two wavelengths to implement a self-referencing technique in order to avoid undesirable power fluctuations influence. The transmittance ratio precision is 0.1%. An analysis has been developed to find the two wavelengths which ratio offers the highest linearity and sensitivity response. Experimental results are successfully compared with theoretical approaches.This work was supported by the Spanish Ministry of Economía y Competitividad and Madrid region under Grants TEC2012–37983-C03–02, P2013/MIT-2790.Publicad

Tolerance analysis for efficient MMI devices in silicon photonics

The proceeding at: IX Conference Silicon Photonics, took place at 2014, March, 8 in S. Francisco (USA).Silicon is considered a promising platform for photonic integrated circuits as they can be fabricated in state-of-the-art electronics foundaries with integrated CMOS electronics. While much of the existing work on CMOS photonics has used directional couplers for power splitting, multimode interference (MMI) devices may have relaxed fabrication requirements and smaller footprints, potentially energy efficient designs. They have already been used as 1x2 splitters, 2x1 combiners in Quadrature Phase Shift Keying modulators, and 3-dB couplers among others. In this work, 3-dB, butterfly and cross MMI couplers are realized on bulk CMOS technology. Footprints from around 40um2 to 200 um2 are obtained. MMI tolerances to manufacturing process and bandwidth are analyzed and tested showing the robustness of the MMI devices.This work has been sponsored by the Spanish institutions Ministerio de Economía y Competitividad under project TEC2012-37983-C03-02, and grant EEBB-1-13-07511, Ministerio de Educación under grant PRX12/00007 and Fundación Caja Madrid.Publicad

Two-Color Pyrometer for Process Temperature Measurement During Machining

A fast fiber-optic two-color pyrometer operating on the optical communication bands is designed for temperature measurements in machining processes. Off-the-shelf low-loss fiber-optic demultiplexers and optoelectronics equipment are used in order to obtain a cost-effective sensing solution while reducing both the temperature measurement error and the minimum measurable temperature. The system is capable of measuring highly localized temperatures without using collimation lens. The designed pyrom-eter allows measuring temperature in the range from 300 to 650 °C, achieving a full-scale temperature error as low as 4%. Factors in-fluencing the temperature measurements are studied in order to identify the sensor limitations, such as a possible damage on the end of the optical fiber, the spectral loss attenuation and responsivity, or the distance between the fiber end and the target. Finally, this pyrometer is applied in a turning process, using a fiber-optic sensor embedded on a standard tool holder. Temperature measurements on the Inconel 718 are reported showing a good agreement with the simulations.This work was supported by the Spanish Ministry of Economía y Competitividad under Grants TEC2012-37983-C03-02, P2013/MIT-2790, and DPI2014-56137-C2-2-R.Publicad

Monitoring techniques in broadband access networks

The proceeding at: 17th International Conference on Transparent Optical Networks, ICTON2015, took place at 2015, July 5-9, in Budapest, (Hungary).Broadband access networks needs specific monitoring techniques at the physical layer to provide the quality of service required by the users. Similarities between sensor and access networks will be analysed to get best practices in both scenarios to provide novel monitoring and self-reference techniques.This work has received funding from the Spanish Ministry of Economía y Competitividad under projects TEC2012-37983-C03-02 (CFOOT-TIC) and TEC2009-14718-C03-03, and support from the Comunidad de Madrid project under grant S2013/MIT-2790 (SINFOTON-CM).publicad