Advanced photonic sensors for industrial applications

380 p.En esta tesis se han desarrollado diversos sensores basados en fibra óptica cuya finalidad es ofrecer una alternativa o solución a las necesidades particulares de la industria. En este contexto, las fibras ópticas y la fotónica en general son especialmente atractivas gracias a características intrínsecas que poseen, como su pequeño tamaño y alta sensibilidad, por ejemplo, lo que ha aumentado el interés por parte del sector industrial en esta tecnología.En la primera parte de la tesis, se describe el proceso llevado a cabo para el diseño y fabricación de sensores ópticos para la medida sin contacto del parámetro llamado Tip Clearance (TC) en motores aeronáuticos. El TC consiste en medir la distancia (del orden de micrómetros) entre los álabes que están girando a altas revoluciones y la carcasa del motor, y, por tanto, es un parámetro de suma importancia para la industria aeronáutica tanto a nivel de seguridad como de eficiencia del motor. Dichos sensores fueron puestos a pruebas en el túnel de viento del Centro de Tecnologías Aeronáutcas (Zamudio, Bizkaia) con buenos resultados.En la segunda parte de la tesis se han diseñado y fabricado sensores basados en fibra multinúcleo particularizados específicamente para la medida de diversos parámetros como la temperatura,vibraciones, curvatura, bending, etc. que son de interés para la industria. Dichos sensores mostraron una alta sensibilidad, lo que unido a su simplicidad y pequeño tamaño los convierte en una alternativa interesante tanto para su integración en cadenas de producción como para su uso en test de validación

Advanced photonic sensors for industrial applications

380 p.En esta tesis se han desarrollado diversos sensores basados en fibra óptica cuya finalidad es ofrecer una alternativa o solución a las necesidades particulares de la industria. En este contexto, las fibras ópticas y la fotónica en general son especialmente atractivas gracias a características intrínsecas que poseen, como su pequeño tamaño y alta sensibilidad, por ejemplo, lo que ha aumentado el interés por parte del sector industrial en esta tecnología.En la primera parte de la tesis, se describe el proceso llevado a cabo para el diseño y fabricación de sensores ópticos para la medida sin contacto del parámetro llamado Tip Clearance (TC) en motores aeronáuticos. El TC consiste en medir la distancia (del orden de micrómetros) entre los álabes que están girando a altas revoluciones y la carcasa del motor, y, por tanto, es un parámetro de suma importancia para la industria aeronáutica tanto a nivel de seguridad como de eficiencia del motor. Dichos sensores fueron puestos a pruebas en el túnel de viento del Centro de Tecnologías Aeronáutcas (Zamudio, Bizkaia) con buenos resultados.En la segunda parte de la tesis se han diseñado y fabricado sensores basados en fibra multinúcleo particularizados específicamente para la medida de diversos parámetros como la temperatura,vibraciones, curvatura, bending, etc. que son de interés para la industria. Dichos sensores mostraron una alta sensibilidad, lo que unido a su simplicidad y pequeño tamaño los convierte en una alternativa interesante tanto para su integración en cadenas de producción como para su uso en test de validación

Modelado teórico y experimental de sensores ópticos para la medida de tip clearance en turbinas

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

Tip-Clearance Measurement in the First Stage of the Compressor of an Aircraft Engine

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.This work has been funded in part by the Fondo Europeo de Desarrollo Regional (FEDER); by the Ministerio de Economia y Competitividad under project TEC2015-638263-C03-1-R; by the Gobierno Vasco/Eusko Jaurlaritza under projects IT933-16 and ELKARTEK; and by the University of the Basque Country UPV/EHU under programmes UFI11/16 and Euskampus

Fabrication Quality Assessment Based on the Coupling of a Dual-Core Microstructured Polymer Optical Fiber

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.This work was supported in part by the European Regional Development Fund, in part by the Ministerio de Economía y Competitividad under project RTI2018-094669-B-C31 and RTC2019-007194-4, and in part by the Gobierno Vasco/Eusko Jaurlaritza under projects IT933-16 and ELKARTEK (KK-2021/00092, KK-2021/00082)

Design, Fabrication and Testing of a High-Sensitive Fibre Sensor for Tip Clearance Measurements

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.This work was funded in part by the Fondo Europeo de Desarrollo Regional (FEDER), in part by the Ministerio de Economia y Competitividad under project TEC2015-638263-C03-1-R, and in part by the Gobierno Vasco/Eusko Jaurlaritza IT933-16 and ELKARTEK (KK-2016/0030, KK-2017/00033, KK-2017/00089 and KK-2016/0059). The work of Josu Amorebieta is supported in part by a PhD fellowship from the Universidad del Pais Vasco/Euskal Herriko Unibertsitatea (UPV/EHU), Vicerrectorado de Euskera y Formacion Continua

Review of a Custom-Designed Optical Sensing System for Aero-Engine Applications

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.This work was supported in part by the European Regional Development Fund, in part by the Ministerio de Economía y Competitividad under project RTI2018-094669-B-C31, and in part by the Gobierno Vasco/Eusko Jaurlaritza under projects IT933-16, ELKARTEK (KK-2018/00078 and KK-2019/00051), EKINTZAILE 01560/2019 and HAZITEK (ZL-2020/00380). The work of J. Amorebieta is supported in part by a PhD fellowship from the University of the Basque Country (UPV/EHU), Vicerrectorado de Euskera y Formación Continua

Carbon-coated fiber for optoelectronic strain and vibration sensing

In this article, we report on a carbon-coated optical fiber that is suitable to be used simultaneously as a transmission medium and as a sensor. It consists of a standard single mode fiber (SMF) sleeved in two layers of coating, which provide protection and isolation from external elements. The inner layer is made of carbon, whereas the outer is made of polymer. When the fiber is subjected to mechanical stress, the electrical resistance of the carbon layer changes accordingly. The voltage variations caused by the former can be measured with high accuracy and without interfering with the light propagating through the SMF. In this work, the feasibility of this operating principle is demonstrated in a low coherence Michelson interferometer in which electrical and optical signals were measured simultaneously and compared to each other. Results indicate that electrical measurements are as precise as the optical ones and with linear behavior, reaching a sensitivity of 1.582 mV/με and able to detect vibrations down to 100 mHz.This work was supported by the grants I + D + i/PID2021-122505OBC31, TED2021-129959B-C21, PDC2022-133053-C21, RTC2019-007194-4 and PDC2022-133885-100 funded by MCIN/AEI/10.13039/501100011033, by “ERDF A way of making Europe”, by the “European Union Next Generation EU/PRTR”. The research work is also supported by the Grant No. IT11452-22 and funded by the Basque Government, by ELKARTEK 2023 (μ4Smart-KK-2023/00016, MINAKU KK-2022/00080 and Ekohegaz II-KK-2023/00051) and by the University of the Basque Country. The work of Josu Amorebieta is funded by a PhD fellowship from the University of the Basque Country

Twin-core fiber sensor integrated in laser cavity

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.This work was supported in part by the European Regional Development Fund, in part by the Ministerio de Economia y Competitividad under projects TEC2015-638263-C03-1-R and PGC2018-101997-B-I00, in part by Ministerio de Ciencia e Innovacion: under projects PID2021-122505OB-C31 and TED2021-129959B-C21, in part by the Gobierno Vasco/Eusko Jaurlaritza under projects IT1452-22 and ELKARTEK (KK 2021/00082 and KK 2021/00092), in part by the Swedish Science Council, Office of Naval Research Global (Award N62909-20-12033) and in part by Vinnova Innovair: Forskningsprojekt inom flygteknik (D.N. 2020-00187). The work of Josu Amorebieta is funded by a PhD fellowship from the University of the Basque Country UPV/EHU. The authors would like to thank Kenny Hey Tow, Erik Zetterlund and Fredrik Laurell for useful discussions and support

Composed multicore fiber structure for direction-sensitive curvature monitoring

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 authors acknowledge the financial support of the Spanish MINECO under Project Nos. PGC2018-101997-B-I00 and RTI2018-094669-B-C31 of the Eusko Jaurlaritza (Basque Government) under Project Nos. IT933-16 and ELKARTEK