Open Access
Egituren egoeraren monitorizaziorako zuntz optikoan oinarritutako sentsore sinplifikatua
(Udako Euskal Unibertsitatea, 2015) Iribas Pardo, Haritz; Sagüés García, Mikel; Mariñelarena Ollacarizqueta, Jon; Loayssa Lara, Alayn; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Brillouin hedatuko denbora eremu optikoaren analisian (BOTDA) oinarritutako sentsoreak, estruktura handien (100 km luzerako estrukturak) deformazioa eta tenperatura neurtzeko gaitasuna dute. Lan honetan, BOTDA konfigurazio sinplifikatua aurkezten dugu. Erabilitako konfigurazioaren helburua sentsorearen prezioa murriztea da, detekzio prozesuan parte hartzen duten seinale optikoen sortze prozesua sinplifikatuz. Proposatutako teknika hau, iturri optiko bati irrati-maiztasun (IM) pultsu modulatu bat aplikatuz sortutako osagai espektralen iragazketa optiko pasiboan oinarritzen da. Laborategiko esperimentuek frogatzen dute tenperatura hedatuko neurriak 1,1 metroko erresoluzioarekin 5 km zuntz optikoan zehar
Open Access
Effects of pump pulse extinction ratio in Brillouin optical time-domain analysis sensors
(Optical Society of America, 2017) Iribas Pardo, Haritz; Mariñelarena Ollacarizqueta, Jon; Feng, Cheng; Urricelqui Polvorinos, Javier; Schneider, Thomas; Loayssa Lara, Alayn; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
We report on two previously unknown non-local effects that have been found to impair Brillouin optical time-domain analysis (BOTDA) sensors that deploy limited extinction ratio (ER) pump pulses. The first one originates in the increased depletion of the pedestal of the pump pulses by the amplified probe wave, which in turn entails a reduced amplification of the probe and a measurement distortion. The second effect is due to the interplay between the transient response of the erbium-doped fiber amplifiers (EDFA) that are normally deployed to amplify the pump and the pedestal of the pump pulses. The EDFA amplification modifies the pedestal that follows the pulses in such a way that it also leads to a distortion of the measured gain spectra after normalization. Both effects are shown to lead to non-local effects in the measurements that have similar characteristics to those induced by pump pulse depletion. In fact, the total depletion factor for calculations of the Brillouin frequency shift (BFS) error in BOTDA sensors is shown to be the addition of the depletion factors linked to the pump pulse as well as the pedestal. A theoretical model is developed to analyze both effects by numerical simulation. Furthermore, the effects are investigated experimentally in long-range BOTDA sensors. The pedestal depletion effect is shown to severely constrain the probe power as well as the minimum ER of the pulses that can be deployed in BOTDA sensors. For instance, it is shown that, in a long-range dual-probe BOTDA, an ER higher that 32-dB, which is above that provided by standard electro-optic modulators (EOM), is necessary to be able to deploy a probe power of -3 dBm, which is the theoretical limit for that type of sensors. Even more severe can be the limitation due to the depletion effect induced by the EDFA transient response. It is found that the impairments brought by this effect are independent of the probe power, hence setting an ultimate limit for the BOTDA sensor performance. Experimentally, a long-range BOTDA deploying a 26-dB ER EOM and a conventional EDFA is shown to exhibit a BFS error higher than 1 MHz even for very small probe power.
Open Access
Gain dependence of measured spectra in coherent Brillouin optical time-domain analysis sensors
(SPIE, 2016) Mariñelarena Ollacarizqueta, Jon; Urricelqui Polvorinos, Javier; Loayssa Lara, Alayn; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
We report on the effects of large pump pulse powers on Brillouin optical time-domain analysis (BOTDA) sensors based on phase-modulated probe wave and coherent detection. It is found that the large Brillouin gain that comes from the use of high power pulses induces a narrowing of the RF phase-shift spectrum that is measured in these sensors. This narrowing leads to a Brillouin frequency shift measurement error when the sensor is configured for dynamic measurements. However, the effect has been found to be less significant than that observed in dynamic slope-assisted BOTDA sensors based on amplitude.
Open Access
Detrimental effects in Brillouin distributed sensors caused by EDFA transient
(Optical Society of America, 2017) Feng, Cheng; Iribas Pardo, Haritz; Mariñelarena Ollacarizqueta, Jon; Schneider, Thomas; Loayssa Lara, Alayn; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
We investigate the deleterious effect and the error in Brillouin optical time-domain analyzers induced by the combination of a low extinction ratio pulse generation with the transient behavior of erbium-doped fiber amplifiers.
Open Access
Phasorial DPP-BOTDA sensor tolerant to non-local effects
(SPIE, 2014) Urricelqui Polvorinos, Javier; Mariñelarena Ollacarizqueta, Jon; Sagüés García, Mikel; Loayssa Lara, Alayn; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
We introduce a modification of the differential pulse width pair technique in a BOTDA sensor based on a phase modulated probe wave and RF demodulation. This provides a differential Brillouin phasorial signal with high spatial and spectral resolution in both components (magnitude and phase shift). Moreover, the use of a phase modulated probe wave provides RF phase shift measurements tolerant to the emergence of non local effects. The combination of both techniques can lead to the development of long range BOTDA sensors. Proof of concept experiments demonstrate RF phase shift measurements with 1m spatial resolution over 50km and an uncertainty of 1.3ºC at the worst contrast position.
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
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
Structural health monitoring of solar trackers using distributed fiber optic sensors
(SPIE, 2019) Mariñelarena Ollacarizqueta, Jon; Mompó Roselló, Juan José; Zurita Gabasa, Jesús; Urricelqui Polvorinos, Javier; Júdez Colorado, Aitor; López-Amo Sáinz, Manuel; Jiménez Romero, Sergio; Achaerandio, Álvaro; Loayssa Lara, Alayn; Institute of Smart Cities - ISC; Gobierno de Navarra / Nafarroako Gobernua, 0011-1365-2017-000122; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
We demonstrate the application of a novel type of distributed fiber optic sensors (DFOSs) to dynamically monitor the effects of wind on solar tracker structures used in photovoltaic power stations. This DFOS is based on the stimulated Brillouin scattering nonlinear optical effect in optical fiber, which can be used to measure the distribution of strain and temperature along a given structure. However, contrary to existing solutions, the sensor provides dynamic real-time measurements with hundreds or even thousands of full simultaneous measurements for all positions in the fiber each second. Moreover, high-precision and high spatial resolution are obtained. This so-called dynamic Brillouin optical time-domain analysis (D-BOTDA) sensor provides real-time monitoring of the bending and torsion of the structure of solar trackers in response to wind load. This helps the solar tracker manufacturer asses and improve the mechanical designs so as to introduce corrective measures and develop cost-effective components that properly withstand the effects of wind at any given location. We experimentally demonstrate the application of a D-BOTDA sensing system to measure distributed bending and, for the first time to our knowledge, also distributed torsion along the stressed beam of the solar tracker. For this purpose, we have developed a procedure to instrument the torsion beam with two optical sensing fibers that are fixed helically wound along the beam in opposite directions, so that any common-mode thermal or bending effects are removed. We initially performed tests in a laboratory facility in which sections of the torsion beam could be subjected to controlled moments. Static and dynamic loads were applied and the measured deformations were compared to those obtained with fiber Bragg gratings, which just provide point measurements of strain. In both cases, full agreement was demonstrated. Finally, the system was installed in an operational solar park.
Open Access
Cost-effective Brillouin optical time-domain analysis sensor using a single optical source and passive optical filtering
(Hindawi Publishing Corporation, 2016) Iribas Pardo, Haritz; Urricelqui Polvorinos, Javier; Mariñelarena Ollacarizqueta, Jon; Sagüés García, Mikel; Loayssa Lara, Alayn; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
We present a simplified configuration for distributed Brillouin optical time-domain analysis sensors that aims to reduce the cost of the sensor by reducing the number of components required for the generation of the two optical waves involved in the sensing process. Te technique is based on obtaining the pump and probe waves by passive optical filtering of the spectral components generated in a single optical source that is driven by a pulsed RF signal. Te optical source is a compact laser with integrated electroabsorption modulator and the optical filters are based on fiber Bragg gratings. Proof-of-concept experiments demonstrate 1m spatial resolution over a 20km sensing fiber with a 0.9MHz precision in the measurement of the Brillouin frequency shiſt, a performance similar to that of much more complex setups. Furthermore, we discuss the factors limiting the sensor performance, which are basically related to residual spectral components in the filtering process.
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.