Open Access
Contribution to the advancement of Brillouin optical time-domain analysis sensors
(2018) Iribas Pardo, Haritz; Loayssa Lara, Alayn; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Distributed fiber optic sensors (DFOS) are becoming an increasingly used technology to monitor the integrity of structures. This is due to the fact that this technology can be embedded within the structure and provide distributed information of several relevant parameters for the structure, such as stress, temperature or strain. In DFOS the fiber itself is the transducer, and the measurement of a given parameter is provided continuously along the fiber at a particular spatial resolution, without blind spots. This is the main advantage of DFOS compared to other sensing technologies, the fact that DFOS provide information of a given parameter over thousands or hundreds of thousands of positions along the optical fiber. Conversely, other sensing technologies only give information over the specific points where they are installed, that is to say, they are point sensors. This characteristic of distributed fiber sensors makes them enormously interesting when many points of a structure need to be monitored. In this case, a single distributed fiber sensor can replace many point sensors, which considerably reduces the cost per sensing point when monitoring large structures. In addition, due to the properties of the optical fiber, these sensors have a better performance compared to other kind of sensors. Among other important features, DFOS present a low signal loss, electromagnetic interference immunity, remote sensing and multiplexing capabilities, light weight, and are chemically passive, which make them a very attractive technology for field measurements. Therefore, DFOS have the added advantage of being electrically, magnetically, and chemically passive, so that can be placed in harsh environments, such as nuclear plants or areas with gas concentration, where, due to the possibility of a short circuit, electronic sensors cannot be placed. Al these characteristics make this technology unique. Among the different types of DFOS, those based on stimulated Brillouin scattering, and more specifically, those that build upon the Brillouin optical time-domain analysis (BOTDA) technique, are one of the most promising. The main characteristic that makes BOTDA sensors as promising, is the ability to perform distributed strain and temperature measurements over long distances at high spatial resolution. For the functioning of the sensor, the general interaction that takes place in the BOTDA technique involves two optical waves: a continuous wave probe and a counter-propagating pump pulse. The performance of the sensor response is limited, among others, by the maximum optical power of both waves that can be injected into the fiber. In this way, the main research line in BOTDA sensors is focused on the study of the physical limitations of the technique as well as the development of solutions to these constraints. Another important line relies on the simplification of the sensor setup so as to reduce the complexity and the cost of the sensor. This thesis dissertation contributes to the development of BOTDA sensors by means of different contributions in these two research lines. Several theoretical and experimental studies have been conducted to accurately determine the main limits to the sensor performance in terms of the maximum optical power of the pump and probe waves that can be used. One of the most important limitation in BOTDA sensors is the onset of non-local effects, which limits the maximum pump and probe waves power that can be injected in the fiber, and hence, the signal-to-noise ratio (SNR) at the receiver is worsen. The so-called non-local effects generate measurement errors, because the Brillouin spectra measured at distant locations depend on the interaction at previous positions in the fiber. In this research line, we have examined the effects caused by the limited extinction ratio (ER) of the pump pulse, finding that, among other impairments, it leads to the onset of a new non-local effect originated in the depletion of the pedestal of the pump wave. In addition, it has been found that the pedestal deformation caused by the transient response of erbium-doped fiber amplifiers, which are typically deployed to amplify the pump pulse, also constrains the performance of the sensor. Another contribution is the study of the techniques presented in the literature to mitigate the impairments caused by second-order non-local effects, which cause a frequency-dependent spectral deformation of the pulse. The findings of this study show that these techniques are only applicable when the Brillouin frequency shift (BFS) of the fiber is uniform, which is hard to find in real applications. Lastly, another subject of study is the limitations of the pump and probe optical power in coded-pump wave BOTDA configurations. We have observed that, in addition to some known limitations, there are two important restrictions that have to be taken into account: the onset of non-local effects and the non-linear amplification of the probe wave, both generated by the successive gain induced by the multiple pulses of the coded-pump wave. As a consequence of the findings of these studies, BOTDA configurations intended to solve these limitations have also been proposed during the thesis work. A technique to mitigate the constraints induced by the limited ER of the pump pulse has been presented. This method is based on adding a dithering to the optical source used to generate the two waves involved in the BOTDA sensor, so that the optical wavelength of both signals is modulated. In this way, the Brillouin interaction between the pedestal and the probe wavefronts become uncorrelated, and hence, the influence of the pedestal is greatly reduced. Another contribution is a technique focused on completely overcome the onset of second-order non-local effects. This method is based on continuously tracking the BFS distribution of the fiber, which combined with the probe-dithering method, has allowed, to the best of our knowledge, to inject the highest demonstrated probe wave power in a BOTDA sensor to date. In addition, in order to improve the SNR of the sensor, a novel BOTDA sensor has been proposed. This analyzer combines mono-color cyclic coding and probe-dithering techniques, so that the impairments caused by a coded pump wave are reduced, and hence, it is possible to increase the optical power and consequently enhance the sensing distance range. Finally, a novel simplified BOTDA sensor has been presented, which relies on passive optical filtering of the spectral components generated in a single optical source. In this way, the sensor setup is simplified reducing the number of optical devices, and therefore, the cost of the sensor is also reduced. This BOTDA configuration has been shown to have a performance comparable to more complex setups.
Open Access
Pulse coding linearization for Brillouin optical time-domain analysis sensors
(Optical Society of America, 2018) Mariñelarena Ollacarizqueta, Jon; Iribas Pardo, Haritz; Loayssa Lara, Alayn; Institute of Smart Cities - ISC
We introduce a simple method to extend the performance of pulse coding techniques in their application to Brillouin optical time-domain analysis sensors (BOTDA). It is based on applying a simple logarithmic processing on the detected probe wave that compensates the deviation from linearity of the sensor response for long code lengths. The technique ensures that the accumulated effect of a sequence of pulses is equal to the linear addition of the effects of the individual components, which is the essential condition to ensure a correct decoding of the probe gain measurement. We experimentally demonstrate the compensation of the Brillouin frequency shift error induced by the accumulated gain nonlinearity. Furthermore, a proof-of-concept 80 km sensing link within a total 200 km fiber loop demonstrated a better than 2 MHz precision with 2 m spatial resolution.
Open Access
Fiber-optic brillouin distributed sensors: from dynamic to long-range measurements
(CRC Press, 2018) Loayssa Lara, Alayn; Urricelqui Polvorinos, Javier; Iribas Pardo, Haritz; Mompó Roselló, Juan José; Mariñelarena Ollacarizqueta, Jon; Estadística, Informática y Matemáticas; Ingeniería Eléctrica, Electrónica y de Comunicación; Estatistika, Informatika eta Matematika; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
This chapter focuses on Brillouin optical time-domain analysis (BOTDA) sensors because they are the most successful Brillouin distributed sensors (BDS) type in terms of performance and practical applications. Distributed sensor featuring can be done in the time, coherence, or frequency domains, giving rise to the three main analysis BDS types: BOTDA, Brillouin optical correlation-domain analysis (BOCDA), and Brillouin optical frequency-domain analysis (BOFDA). The distance range of measurements performed using a BOTDA sensor is given by the length of sensing fiber that the system is able to measure with a specified performance in terms of measurement precision and time. The chapter reviews the fundamentals and the research directions in BDSs. The applications of the technology are multiple and in diverse fields¿for instance, in the oil and gas industry, where BDSs have been applied to measure temperature and strain along the umbilical cables used for subsea wells.
Open Access
Non-local effects in Brillouin optical time-domain analysis sensors
(MDPI, 2017) Iribas Pardo, Haritz; Urricelqui Polvorinos, Javier; Mompó Roselló, Juan José; Mariñelarena Ollacarizqueta, Jon; Loayssa Lara, Alayn; Institute of Smart Cities - ISC; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Brillouin optical time-domain analysis (BOTDA) sensors have great potential to provide distributed measurements of temperature and strain over large structures with high spatial resolution and measurement precision. However, their performance ultimately depends on the amount of probe and pump pulse power that can be injected into the sensing fiber, which determines the signal-to-noise ratio of the detected measurement signal. The probe wave power is constrained by the generation of noise induced by spontaneous Brillouin scattering and at lower power by the so-called non-local effects. In this work, we focus on the latter. We review the physical origins of non-local effects and analyze the performance impairments that they bring. In addition, we discuss the different methods that have been proposed to counteract these effects comparing their relative merits and ultimate performance. Particularly, we focus on a technique that we have devised to compensate non-local effects which is based on introducing an optical frequency modulation or dithering to the probe wave. This method is shown to provide a comprehensive solution to most of the impairments associated with non-local effects and also to enable some side benefits, such as amplification of the pump pulses to compensate the attenuation of the fiber.
Open Access
Un paseo por la Rochapea en Pamplona... con una mirada matemática. Guía para el profesorado
(Ayuntamiento de Pamplona, 2023) Iribas Pardo, Haritz; Abaurrea Larrayoz, Jaione; Wilhelmi, Miguel R.; Lasa Oyarbide, Aitzol; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika
Se ha diseñado una ruta matemática por el barrio pamplonés de la Rochapea. Contiene problemas matemáticos a resolver in situ por el alumnado de 6º de Educación Primaria y 2º de Educación Secundaria en relación con unas determinadas localizaciones de interés (lugares, edificios o esculturas, elementos del mobiliario urbano...). Los problemas o retos matemáticos son adecuados a los estándares de aprendizaje oficiales de la asignatura de matemáticas en los niveles indicados. Se proporciona información o pistas tanto gráfica como textual para su resolución.
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Lehen hezkuntzako ikasleei zuzendutako aplikazio interaktiboa, adobe flash, PHO eta MySQL teknologietan oinarritua
(2009) Iribas Pardo, Haritz; Sagüés García, Mikel; Escuela Técnica Superior de Ingenieros Industriales y de Telecomunicación; Telekomunikazio eta Industria Ingeniarien Goi Mailako Eskola Teknikoa; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
Open Access
Latest research on long-range Brillouin distributed sensing
(SPIE, 2019) Loayssa Lara, Alayn; Urricelqui Polvorinos, Javier; Iribas Pardo, Haritz; Mariñelarena Ollacarizqueta, Jon; Mompó Roselló, Juan José; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute for Advanced Materials and Mathematics - INAMAT2; Ingeniería Eléctrica, Electrónica y de Comunicación; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa; Gobierno de Navarra / Nafarroako Gobernua projecto 0011-1365-2017-000122
We review the latest developments in long-range Brillouin optical time-domain analysis sensors. The factors that impair the performance of these sensors, particularly in terms of their distance range, are discussed together with the latest methods to overcome them. We focus on our recent contributions based on the application of the probe dithering method, which is based on introducing a wavelength modulation to the probe wave. This technique is shown to effectively compensate nonlocal effects originated in the depletion of the pump pulse as well as of its pedestal. In addition, it can provide amplification to the pump wave with a slight modification of the setup. Furthermore, this method can be combined with pump pulse coding and a new technique for coding linearization that we have devised to further extend the sensing length into the hundreds of kilometers range.
Open Access
Unibertsitateko irakaslegaiek Lehen Hezkuntzako ikasleentzat Txikipedian sortutako matematikako edukien egokitasuna neurtzen
(Udako Euskal Unibertsitatea, UEU, 2022-12-02) Iribas Pardo, Haritz; Errazkin Vicente, Aitor; Torrealday Gallarreta, Amaia; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika
Artikulu honek baliozkotze-prozesu bat biltzen du, zeinak egiaztatu nahi izan duen Lehen Hezkuntzako ikasleek matematikako edukiak ulertzeko Txikipedia lagungarri izan duten ala ez, bai testuari zein testuaren osagarri diren ikus-entzunezkoei erreparatuta. Txikipediako matematikako edukiak Mondragon Unibertsitateko Lehen Hezkuntza Graduan irakasle izateko ikasketak egiten ari diren ikasleek sortu dituzte eta Euskal Herriko sei ikastetxetan baliozkotu dira. Emaitzek erakutsi dute Txikipediako sarrerak irakurtzea lagungarria dela ikasleentzat, nahiz eta ikusentzunezkoen ekarpenarekin lotutako emaitzek galdera berriak sorrarazi dituzten. Hala ere, esan dezakegu humanitate digitalek lagun dezaketela matematikaren irakaskuntza hobetzen, bai irakaslegaien formakuntzan zein ikasleen edukien ulermenean ere.
Open Access
Enhanced tolerance to pulse extinction ratio in Brillouin optical time domain analysis sensors by dithering of the optical source
(SPIE, 2015) Iribas Pardo, Haritz; Urricelqui Polvorinos, Javier; Sagüés García, Mikel; Loayssa Lara, Alayn; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
We demonstrate the relaxation of the stringent requirements placed on the pulse extinction ratio in long-range Brillouin optical time-domain analysis sensors (BOTDA) by modulating the wavelength of the laser source that is used to generate both pump and probe waves. This modulation makes the counter-propagating pulse pedestal and probe waves to become correlated only at certain locations in the fiber, thus reducing the gain experienced by the probe wave, which is precisely the process that limits the performance in long-range BOTDAs. Proof-of-concept experimental results in a 20-km sensing link demonstrate a 6-dB reduction of the required modulator extinction ratio.
Open Access
Eman dezagun paseo bat Iruñeko Arrotxapean barna... baina ikus dezagun hiria matematiken begiradatik. Jarduera-koadernoa
(Ayuntamiento de Pamplona, 2023) Iribas Pardo, Haritz; Abaurrea Larrayoz, Jaione; Wilhelmi, Miguel R.; Lasa Oyarbide, Aitzol; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika
Iruñeko Arrotxapea auzotik ibilbide matematiko bat diseinatu da. Lehen Hezkuntzako 6. mailako eta Bigarren Hezkuntzako 2. mailako ikasleek tokian bertan ebatzi beharreko arazo matematikoak dituzte, kokapen interesgarri jakin batzuei lotuta (lekuak, eraikinak edo eskulturak, hiri-altzarien elementuak…). Problema edo erronka matematikoak egokiak dira matematika irakasgaiaren ikaskuntza-estandar ofizialetarako, adierazitako mailetan. Informazioa edo pistak ematen dira, bai grafikoak, bai testualak, ebazteko.