Design and fabrication of customized fiber gratings to improve the interrogation of optical fiber sensors

[EN] Fiber grating sensors and devices have demonstrated outstanding capabilities in both telecommunications and sensing areas, due to their well-known advantageous characteristics. Therefore, one of the most important motivations lies in the potential of customized fiber gratings to be suitably employed for improving the interrogation process of optical fiber sensors and systems. This Ph.D. dissertation is focused on the study, design, fabrication and performance evaluation of customized fiber Bragg gratings (FBGs) and long period gratings (LPGs) with the double aim to present novel sensing technologies and to enhance the response of existing sensing systems. In this context, a technique based on time-frequency domain analysis has been studied and applied to interrogate different kind of FBGs-based sensors. The distribution of the central wavelength along the sensing structures has been demonstrated, based on a combination of frequency scanning of the interrogating optical pulse and optical time-domain reflectometry (OTDR), allowing the detection of spot events with good performance in terms of measurand resolution. Moreover, different customized FBGs have been interrogated using a technology inspired on the operation principle of microwave photonics (MWP) filters, enabling the detection of spot events using radio-frequency (RF) devices with modest bandwidth. The sensing capability of these technological platforms has been fruitfully employed for implementing a large scale quasi-distributed sensor, based on an array of cascaded FBGs. The potentiality of LPGs as fiber optic sensors has also been investigated in a new fashion, exploiting the potentials of MWP filtering techniques. Besides, a novel approach for simultaneous measurements based on a half-coated LPG has been proposed and demonstrated. Finally, the feasibility of FBGs as selective wavelength filters has been exploited in sensing applications; an alternative approach to improve the response and performance of Brillouin distributed fiber sensors has been studied and validated via experiments. The performance of the reported sensing platforms have been analyzed and evaluated so as to characterize their impact on the fiber sensing field and to ultimately identify the use of the most suitable technology depending on the processing task to be carried out and on the final goal to reach.[ES] Los sensores y dispositivos en fibra basados en redes de difracción han mostrado excepcionales capacidades en el ámbito de las telecomunicaciones y del sensado, gracias a sus excelentes propiedades. Entre las motivaciones más estimulantes destaca la posibilidad de fabricar redes de difracción ad-hoc para implementar y/o mejorar las prestaciones de los sensores fotónicos. Esta tesis doctoral se ha enfocado en el estudio, diseño, fabricación y evaluación de las prestaciones de redes de difracción de Bragg (FBGs) y de redes de difracción de periodo largo (LPGs) personalizadas con el fin de desarrollar nuevas plataformas de detección y a la vez mejorar la respuesta y las prestaciones de los sensores fotónicos ya existentes. En este contexto, una técnica basada en el análisis tiempofrecuencia se ha estudiado e implementado para la interrogación de sensores en fibra basados en varios tipos y modelos de FBGs. Se ha analizado la distribución de la longitud de onda central a lo largo de la estructura de sensado, gracias a una metodología que conlleva el escaneo en frecuencia del pulso óptico incidente y la técnica conocida como reflectometria óptica en el dominio del tiempo (OTDR). De esta manera se ha llevado a cabo la detección de eventos puntuales, alcanzando muy buenas prestaciones en términos de resolución de la magnitud a medir. Además, se han interrogado varias FBGs a través de una técnica basada en el principio de operación de los filtros de fotónica de microondas (MWP), logrando así la detección de eventos puntuales usando dispositivos de radio-frecuencia (RF) caracterizados por un moderado ancho de banda. La capacidad de sensado de estas plataformas tecnológicas ha sido aprovechada para la realización de un sensor quasi-distribuido de gran alcance, formado por una estructura en cascada de muchas FBGs. Por otro lado, se han puesto a prueba las capacidades de las LPGs como sensores ópticos según un enfoque novedoso; para ello se han aprovechados las potencialidades de los filtros de MWP. Asimismo, se ha estudiado y demostrado un nuevo método para medidas simultáneas de dos parámetros, basado en una LPG parcialmente recubierta por una película polimérica. Finalmente, se ha explotado la viabilidad de las FBGs en cuanto al filtrado selectivo en longitud de onda para aplicaciones de sensado; para ello se ha propuesto un sistema alternativo para la mejora de la respuesta y de las prestaciones de sensores ópticos distribuidos basados en el scattering de Brillouin. En conclusión, se han analizado y evaluado las prestaciones de las plataformas de sensado propuestas para caracterizar su impacto en el ámbito de los sistemas de detección por fibra y además identificar el uso de la tecnología más adecuada dependiendo de la tarea a desarrollar y del objetivo a alcanzar.[CA] Els sensors i dispositius en fibra basats en xarxes de difracció han mostrat excepcionals capacitats en l'àmbit de les telecomunicacions i del sensat, gràcies a les seus excel¿lents propietats. Entre les motivacions més estimulants destaca la possibilitat de fabricar xarxes de difracció ad-hoc per a implementar i/o millorar les prestacions de sensors fotònics. Esta tesi doctoral s'ha enfocat en l'estudi, disseny, fabricació i avaluació de les prestacions de xarxes de difracció de Bragg (FBGs) i de xarxes de difracció de període llarg (LPGs) personalitzades per tal de desenvolupar noves plataformes de detecció i al mateix temps millorar la resposta i les prestacions dels sensors fotònics ja existents. En este context, una tècnica basada en l'anàlisi temps-freqüència s'ha estudiat i implementat per a la interrogació de sensors en fibra basats en diversos tipus i models de FBGs. S'ha analitzat la distribució de la longitud d'ona central al llarg de l'estructura de sensat, gràcies a una metodologia que comporta l'escaneig en freqüència del pols òptic incident i la tècnica coneguda com reflectometria òptica en el domini del temps (OTDR). D'esta manera s'ha dut a terme la detecció d'esdeveniments puntuals, aconseguint molt bones prestacions en termes de resolució de la magnitud a mesurar. A més, s'han interrogat diverses FBGs a través d'una tècnica basada en el principi d'operació dels filtres de fotònica de microones (MWP), aconseguint així la detecció d'esdeveniments puntuals utilitzant dispositius de ràdio-freqüència (RF) caracteritzats per un moderat ample de banda. La capacitat de sensat d'aquestes plataformes tecnològiques ha sigut aprofitada per a la realització d'un sensor quasi-distribuït a llarga escala, format per una estructura en cascada de moltes FBGs. D'altra banda, s'han posat a prova les capacitats de les LPGs com a sensors òptics segons un enfocament nou; per a això s'han aprofitat les potencialitats dels filtres de MWP. Així mateix, s'ha estudiat i demostrat un nou mètode per a mesures simultànies de dos paràmetres, basat en una LPG parcialment recoberta per una pel¿lícula polimèrica. Finalment, s'ha explotat la viabilitat de les FBGs pel que fa al filtrat selectiu en longitud d'ona per a aplicacions de sensat; per això s'ha proposat un sistema alternatiu per a la millora de la resposta i de les prestacions de sensors òptics distribuïts basats en el scattering de Brillouin. S'han analitzat i avaluat les prestacions de les plataformes de sensat propostes per a caracteritzar el seu impacte en l'àmbit dels sistemes de detecció per fibra i a més identificar l'ús de la tecnologia més adequada depenent de la tasca a desenvolupar i de l'objectiu a assolir.Ricchiuti, AL. (2016). Design and fabrication of customized fiber gratings to improve the interrogation of optical fiber sensors [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/66343TESISPremiad

Spot events detection along a large scale sensor based on ultra weak FBGs using time-frequency analysis

[EN] A simple scheme for interrogating a 5 m-long photonics device and its potential applications to quasi-distributed fiber sensing is proposed. The sensor consists of an array of 500 identical very weak fiber Bragg gratings (FBGs). The gratings are 9 mm-long and have been serially written in cascade along a single optical fiber. The measurement system is based on a combination of optical time domain reflectrometry (OTDR) and frequency scanning of the interrogating pulse. The time-frequency analysis is performed by launching an optical pulse into the sensor and by retrieving and analyzing the back-reflected signal. The measurement of the temperature, length and position of spot events along the sensors is demonstrated, with good accuracy. As both spatial and temperature resolution of the method depend on the input pulse duration, the system performance can be controlled and optimized by properly choosing the temporal duration of the interrogating pulse. A spatial resolution of 9 mm (ultimately dictated by one grating length) has been obtained with an 80 ps optical pulse; while a temperature resolution of less than 0.42 K has been demonstrated using a 500 ps incident pulse. The sensor proposed proves to be simple, robust, polarization insensitive and alleviates the instrumentation complexity for distributed sensing applications.Ministerio de Educacion, Cultura y Deporte; Ministerio de Economia y Competitividad (TEC2014-60378-C2-1-R); Generalitat Valenciana (GRISOLIA/2013/034); Research Excellency Award Program (GVA PROMETEO 2013/012).Ricchiuti, AL.; Sales Maicas, S. (2016). Spot events detection along a large scale sensor based on ultra weak FBGs using time-frequency analysis. Applied Optics. 55(5):1054-1060. https://doi.org/10.1364/AO.55.001054S1054106055

(Invited) Cascade FBGs distributed sensors interrogation using microwave photonics filtering techniques

Systems to interrogate photonic sensors based on long fiber Bragg gratings (FBGs) are illustrated and experimentally validated. The FBGs-based devices are used as quasi-distributed sensors and have demonstrated their ability to detect and measure the precise location of several spot events. The principle of operation is based on a technique used to analyze microwave photonics (MWP) filters. The overall idea beyond this work has been borne out and demonstrated step by step starting from preliminary test that have led to the development of a very-long distributed sensor based on an array of 500 equal and weak FBGs. Firstly, we have demonstrated the feasibility of the MWP filtering technique to interrogate a 10 cm-long high reflectivity (&#8776;99%) FBG. Then, a pair of low-reflectivity (<6%) FBGs has been employed as sensing device. The latter has laid the foundation for the development and implementation of a 5 m-long fiber optic sensor based on 500 very weak FBGs. Spot events have been detected with a good spatial accuracy of less than 1 mm using a modulator and a photo-detector (PD) with a modest bandwidth of only 500 MHz. The simple proposed schemes result cost effective, intrinsically robust against environmental changes and easy to reconfigure.This work was support by the Accion Financiada por el Ministerio de Educacion, Cultura y Deporte within the framework of the Programa de Campus de Excelencia Internacional VLC/Campus, by the Spanish MINECO through projects TEC2014-60378-C2-1-R, by the Grant of the program SANTIAGO GRISOLIA (Grant number GRISOLIA/2013/034), and by the Research Excellency Award Program GVA PROMETEO 2013/012.Ricchiuti, AL.; Hervás-Peralta, J.; Sales Maicas, S. (2016). (Invited) Cascade FBGs distributed sensors interrogation using microwave photonics filtering techniques. Optics and Laser Technology. 77(3):144-150. https://doi.org/10.1016/j.optlastec.2015.09.003S14415077

Temperature gradient sensor based on a long-fiber Bragg grating and time-frequency analysis

© [2014 Optical Society of America.]. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modifications of the content of this paper are prohibited.A photonic sensor based on a 10-cm-long fiber Bragg grating (FBG) is presented and experimentally validated that is dedicated to detect the presence and the position of a temperature gradient. The system is based on the measurement of the central frequency distribution of the grating based on time-frequency domain analysis. A short optical pulse, having duration much shorter than the transit time along the grating, is coupled into the FBG, and the back-reflected pulse is scanned by means of an oscilloscope. A spatial resolution of 1 mm, given by half the input pulse duration, is achieved. The proposed sensor is based on a simple configuration and presents a sensing range of 10 cm, which could be further enhanced by fabricating a longer grating. (C) 2014 Optical Society of AmericaThe authors wish to acknowledge the Infraestructura FEDER UPVOV08-3E-008, FEDER UPVOV10-3E-492, the Spanish MCINN through the project TEC2011-29120-C05-05, the Valencian Government through the Ayuda Complementaria ACOMP/2013/146 and the financial support given by the Research Excellency Award Program GVA PROMETEO 2013/012.Ricchiuti, AL.; Barrera Vilar, D.; Nonaka, K.; Sales Maicas, S. (2014). Temperature gradient sensor based on a long-fiber Bragg grating and time-frequency analysis. Optics Letters. 39(19):5729-5731. https://doi.org/10.1364/OL.39.005729S572957313919Culshaw, B. (2004). Optical Fiber Sensor Technologies: Opportunities and—Perhaps—Pitfalls. Journal of Lightwave Technology, 22(1), 39-50. doi:10.1109/jlt.2003.822139Kersey, A. D., Davis, M. A., Patrick, H. J., LeBlanc, M., Koo, K. P., Askins, C. G., … Friebele, E. J. (1997). Fiber grating sensors. Journal of Lightwave Technology, 15(8), 1442-1463. doi:10.1109/50.618377Li, S. Y., Ngo, N. Q., Tjin, S. C., Shum, P., & Zhang, J. (2004). Thermally tunable narrow-bandpass filter based on a linearly chirped fiber Bragg grating. Optics Letters, 29(1), 29. doi:10.1364/ol.29.000029Uno, H., Kojima, A., Shibano, A., & Mikami, O. (1999). Optical wavelength switch using strain-controlled fiber Bragg gratings. Optical Engineering for Sensing and Nanotechnology (ICOSN ’99). doi:10.1117/12.347816Azana, J., & Muriel, M. A. (2001). Temporal self-imaging effects: theory and application for multiplying pulse repetition rates. IEEE Journal of Selected Topics in Quantum Electronics, 7(4), 728-744. doi:10.1109/2944.974245Volanthen, M., Geiger, H., & Dakin, J. P. (1997). Distributed grating sensors using low-coherence reflectometry. Journal of Lightwave Technology, 15(11), 2076-2082. doi:10.1109/50.641525Hotate, K., & Kajiwara, K. (2008). Proposal and experimental verification of Bragg wavelength distribution measurement within a long-length FBG by synthesis of optical coherence function. Optics Express, 16(11), 7881. doi:10.1364/oe.16.007881Sancho, J., Chin, S., Barrera, D., Sales, S., & Thévenaz, L. (2013). Time-frequency analysis of long fiber Bragg gratings with low reflectivity. Optics Express, 21(6), 7171. doi:10.1364/oe.21.007171Ricchiuti, A. L., Barrera, D., Sales, S., Thevenaz, L., & Capmany, J. (2013). Long fiber Bragg grating sensor interrogation using discrete-time microwave photonic filtering techniques. Optics Express, 21(23), 28175. doi:10.1364/oe.21.028175Thévenaz, L., Chin, S., Sancho, J., & Sales, S. (2014). Novel technique for distributed fibre sensing based on faint long gratings (FLOGs). 23rd International Conference on Optical Fibre Sensors. doi:10.1117/12.2059668Barnoski, M. K., Rourke, M. D., Jensen, S. M., & Melville, R. T. (1977). Optical time domain reflectometer. Applied Optics, 16(9), 2375. doi:10.1364/ao.16.00237

Long Weak FBG Sensor Interrogation Using Microwave Photonics Filtering Technique

“© © 20xx IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.”A system to interrogate photonic sensors based on long weak fiber Bragg gratings (FBGs) is illustrated and experimentally demonstrated. The FBG sensor is able to detect and measure the precise location of several spot events. The principle of operation is based on a technique used to analyze microwave photonics filters. The long weak FBGs are used as quasi-distributed sensors. Several events can be detected along the FBG device with a spatial accuracy of <1 mm using a modulator and a photodetector with a modest bandwidth of <500 MHz. The simple proposed scheme is intrinsically robust against environmental changes and easy to reconfigure.This work was supported in part by the COST Action under Grant TD1001 through the OFSeSa Project, in part by the Infraestructura through the Federacion Espanola de Enfermedades Raras Project under Grant UPVOV08-3E-008 and Grant UPVOV10-3E-492, in part by the Spanish Ministerio de Ciencia e Innovacion under Project TEC2011-29120-C05-05, in part by the Valencia Government through the Ayuda Complementaria Project under Grant ACOMP/2013/146, in part by the Research Excellency Award Program GVA PROMETEO under Grant 2013/012, and in part by the Swiss Commission for Technology and Innovation under Project 13122.1.Lavinia Ricchiuti, A.; Barrera Vilar, D.; Sales Maicas, S.; Thevenaz, L.; Capmany Francoy, J. (2014). Long Weak FBG Sensor Interrogation Using Microwave Photonics Filtering Technique. IEEE Photonics Technology Letters. 26(20):2039-2042. https://doi.org/10.1109/LPT.2014.2345611S20392042262

Microwave photonics filtering technique for interrogating long weak fiber Bragg grating sensors

A system to interrogate photonic sensors based on long weak fiber Bragg gratings (FBGs) is presented and experimentally demonstrated, dedicated to measure the precise location of several spot events. The principle of operation is based on a technique used to analyze microwave photonics (MWP) filters. The long weak FBGs are used as quasi-distributed sensors. Several events can be detected along the FBG device with a spatial accuracy under 1 mm using a modulator and a photo-detector (PD) with a modest bandwidth of less than 500 MHz. The simple proposed scheme is intrinsically robust against environmental changes and easy to reconfigure

Simultaneous measurement of humidity and temperature based on a partially coated optical fiber long period grating

A humidity and temperature optical fiber sensor based on a long-period grating (LPG), which can provide simultaneous response to both magnitudes, is proposed and demonstrated via experiments. Previously, the LPG was fully coated with humidity sensitive nanostructured polymeric thin films by the Layer-by-Layer (LbL) nano assembly technique. Hence the surrounding refractive index was changed, so provoking wavelength shifts of the attenuation bands of the transmission spectrum. This fully coated LPG was exposed to relative humidity (RH) and temperature tests, varying from 20% to 80% RH and from 25 to 85ºC, respectively. Then, half of the LPG coating was chemically removed and this results in the splitting of the main attenuation band into two different contributions. When this semi-coated LPG was also exposed to RH and temperature tests, the new two attenuation bands presented different behaviors for humidity and temperature. This novel dual-wavelength based sensing method enables the simultaneous measurement of RH and temperature using only one LPG.This work was supported in part by the Spanish Ministry of Economy and Competitiveness - through the projects CICYT-FEDER TEC2013-43679-R and TEC2014-60378-C2-1-R. It was also supported by a UPNA pre-doctoral research grant, by the Program of International Excellence Campus VLC/Campus, by the grant of program SANTIAGO GRISOLIA, and by the Research Excellency Award Program GVA PROMETEO 2013/012.Urrutia, A.; Goicoechea, J.; Ricchiuti, AL.; Barrera Vilar, D.; Sales Maicas, S.; Arregui, FJ. (2016). Simultaneous measurement of humidity and temperature based on a partially coated optical fiber long period grating. Sensors and Actuators B: Chemical. 227(5):135-141. https://doi.org/10.1016/j.snb.2015.12.031S135141227

Microwave photonics filtering technique for interrogating a very-weak fiber Bragg grating cascade sensor

A system to interrogate photonic sensors based on a very weak fiber Bragg grating cascade fiber is presented and experimentally validated and dedicated to detecting the presence and location of a spot event. The distributed sensor proposed consists of a 5-m-long fiber, containing 500 9-mm-long Bragg gratings with a grating separation of 10.21 mm. The principle of operation is based on a technique used to analyze microwave photonics filters. The detection of spot events along the sensor is demonstrated with remarkable accuracy under 1 mm, using a photodetector and a modulator with a bandwidth of only 500 MHz. The simple proposed scheme is intrinsically robust against environmental changes and is easy to reconfigure.This work was supported in part by the Infraestructura FEDER UPVOV08-3E-008, by FEDER UPVOV10-3E-492, by the Spanish MCINN through Project TEC2011-29120-C05-05, by the Valencia Government through Ayuda Complementaria ACOMP/2013/146, by the grant of the program SANTIAGO GRISOLIA, and by the Research Excellency Award Program GVA PROMETEO 2013/012.Ricchiuti, AL.; Hervás Peralta, J.; Barrera Vilar, D.; Sales Maicas, S.; Capmany Francoy, J. (2014). Microwave photonics filtering technique for interrogating a very-weak fiber Bragg grating cascade sensor. IEEE Photonics Journal. 6(6). https://doi.org/10.1109/JPHOT.2014.2363443S6

Microwave Photonics for Optical Sensors

[EN] This paper presents a review and discussion of the applications of Microwave Photonic techniques and functionalities to the field of optical fiber sensors. A specific end-to end model for its characterization is presented here for the first time that yields the sensitivity of the different figures of merit in terms of measurand variations. Experimental techniques to characterize these systems are presented and applications of two specific microwave photonic functionalities to high-resolution discrete and quasi-distributed optical sensing are illustrated. Future directions of research are also highlighted.This work was supported in part by the Spanish MINECO through projects TEC2014-60378-C2-1-R MEMES and in part by the Government of Valencia through the Research Excellency Award Program GVA PROMETEO II/2013/012. The work of J. Hervas was supported by the MECD FPU scholarship (FPU13/04675). The work of Ming Li was supported in part by the National Natural Science Foundation of China under Grants 61377002, 61522509, and 61535012and in part by the Thousand Young Talent programHervás-Peralta, J.; Ricchiuti, AL.; Li, W.; Zhu, NH.; Fernandez-Pousa, CR.; Sales Maicas, S.; Li, M.... (2017). Microwave Photonics for Optical Sensors. IEEE Journal of Selected Topics in Quantum Electronics. 23(2):1-13. https://doi.org/10.1109/JSTQE.2017.2651117S11323

Study of the Interference Affecting the Performance of the Theremin

The theremin is one of the earliest electronic musical instruments. It is named after the Russian physics Professor Lev S. Termen who invented it in 1919. This musical instrument belongs to a very short list of devices which are played without physical contact between the musician and the instrument. theremin players complain about the interference that any object in a radius of approximately 3 meters produces when playing the theremin, modifying the intonation of the instrument. This is a problem when playing in small scenarios, with other musicians which move around it. With the aim of reducing the degree of interference from nearby obstacles, some metallic isolating bars conforming an antenna array can be placed around the theremin pitch antenna. The paper shows different simulations calculated with the commercial software Ansoft HFSS, a tool which allows three-dimensional full wave electromagnetic field simulation, with radio frequencies, millimeter and micro waves, and experimental measures, both showing a reduction in the effect of the interference.Bachiller Martin, MC.; Sastre Martinez, J.; Ricchiuti, AL.; Esteban González, H.; Hernandez Franco, CA. (2012). Study of the Interference Affecting the Performance of the Theremin. International Journal of Antennas and Propagation. 2012:1-9. doi:10.1155/2012/348151S192012Buller, W., & Wilson, B. (2006). Measurement and Modeling Mutual Capacitance of Electrical Wiring and Humans. IEEE Transactions on Instrumentation and Measurement, 55(5), 1519-1522. doi:10.1109/tim.2006.88029