Open Access
Real-time FFT analysis for interferometric sensors multiplexing
(IEEE / OSA, 2015) Leandro González, Daniel; Bravo Acha, Mikel; Ortigosa Cayetano, Amaia; López-Amo Sáinz, Manuel; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
In this paper, a theoretical and experimental study of two interferometric sensor multiplexing schemes has been carried out by means of the fast Fourier transform (FFT) analysis. This work addresses one of the main drawbacks of photonic crystal fiber (PCF) sensors, that is, its multiplexing capability. Using a commercial optical interrogator combined with a simple FFT measurement technique, the simultaneous real-time monitoring of several PCF sensors is achieved. A theoretical analysis has been performed where simulations matched with the experimental results. For the experimental verification, highly birefringent (HiBi) fiber sections that operated as sensing elements were multiplexed and tested in two configurations. Due to the FFT analysis, both multiplexing schemes can be properly interrogated by monitoring the FFT phase change at the characteristic spatial-frequency of each sensor. For this purpose a commercial interrogator and a custom Matlab program were used for computing the FFT and for monitoring the FFT phase change in real-time (1 Hz).
Open Access
Multiplexing of six micro-displacement suspended-core Sagnac interferometer sensors with a Raman-Erbium fiber laser
(Optical Society of America, 2013) Bravo Acha, Mikel; Fernández Vallejo, Montserrat; Echapare Zabaleta, Mikel; López-Amo Sáinz, Manuel; Kobelke, J.; Schuster, K.; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
This work experimentally demonstrates a long-range optical fiber sensing network for the multiplexing of fiber sensors based on photonic crystal fibers. Specifically, six photonic crystal fiber sensors which are based on a Sagnac interferometer that includes a suspended-core fiber have been used. These sensors offer a high sensitivity for microdisplacement measurements. The fiber sensor network presents a ladder structure and its operation mode is based on a fiber ring laser which combines Raman and Erbium doped fiber amplification. Thus, we show the first demonstration of photonic crystal fiber sensors for remote measurement applications up to 75 km.
Open Access
Development of a water flow and velocity optical fiber sensor for field testing
(Optica Publishing Group, 2022) Rodríguez Rodríguez, Armando; Urroz Unzueta, José Carlos; Diéguez Elizondo, Pedro; Bravo Acha, Mikel; López-Amo Sáinz, Manuel; López Rodríguez, José Javier; Ingeniería; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute of Smart Cities - ISC; Ingeniaritza; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
A water flow and velocity fiber optic sensor system was developed and tested. The sensing head was especially developed and ruggedized to measure velocities at different depths, in order to calculate the discharge in channels.
Open Access
WDM and TDM interrogation by sequentially pulsing direct modulated DFBs
(Optica, 2020) Pérez González, Asier; Bravo Acha, Mikel; Leandro González, Daniel; Pérez Herrera, Rosa Ana; López-Amo Sáinz, Manuel; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC
A new versatile and cost-effective interrogation system by pulsing direct modulated (DM) DFB laser diodes is proposed. 1 pm wavelength resolution and 600 m sensor spacing is demonstrated by sequentially pulsing a DM DFB.
Open Access
One-year analysis of road condition using FBG arrays
(SPIE, 2023) Corera Orzanco, Íñigo; Pradas Martínez, Javier; Leandro González, Daniel; Bravo Acha, Mikel; López-Amo Sáinz, Manuel; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa, PJUPNA06-2022
In this work, it is presented an analysis of FBG arrays installed in a public road. The arrays were installed in a newly paved urban road and were monitored for more than one year. The study evidences the permanent deformation of the wearing course and the degradation of the reflected spectra of the sensors.
Open Access
Random DFB fiber laser for remote (200 km) sensor monitoring using hybrid WDM/TDM
(IEEE, 2016) Leandro González, Daniel; Miguel Soto, Verónica de; Pérez Herrera, Rosa Ana; Bravo Acha, Mikel; López-Amo Sáinz, Manuel; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
In this paper, a random distributed feedback fiber laser is proposed as a multiplexing scheme for ultralong range measurements (up to 200 km). Optical fiber sensors are time and wavelength multiplexed overcoming one of the main limitations of long-range sensing setups, which is their limited multiplexing capability. The direct modulation of the laser's cavity allows the interrogation of sensors by measuring the reflected power for different wavelengths and distances. Fiber Bragg gratings placed at different fiber locations and wavelengths have been interrogated in two different sensor networks. In addition, in order to improve the performance of the system, some features have been analyzed.
Open Access
Internal modulation of a Random fiber laser
(Optical Society of America, 2013) Bravo Acha, Mikel; Fernández Vallejo, Montserrat; López-Amo Sáinz, Manuel; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
A characterization of a modulated random mirror laser has been experimentally carried out. Unlike conventional internally modulated fiber lasers, no distortion of the modulating frequency or self-mode-locking effects were measured. The behavior of the laser using pulsed and analog modulation up to 12 GHz is shown.
Open Access
Application of remote power-by-light switching in a simplified BOTDA sensor network
(MDPI, 2013) Bravo Acha, Mikel; Zornoza Indart, Ander; Loayssa Lara, Alayn; López-Amo Sáinz, Manuel; López Higuera, José Miguel; Ullán Nieto, Ángel; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
We propose and demonstrate the use of spatial multiplexing as a means to reduce the costs of distributed sensing networks. We propose a new scheme in which remote power-by-light switching is deployed to scan multiple branches of a distributed sensing network based on Brillouin Optical Time Domain Analysis (BOTDA) sensors. A proof-of-concept system is assembled with two 5-km sensor fiber branches that are alternatively monitored using a fast remotely controlled and optically powered optical switch. The multiplexed distributed sensor fibers were located 10 km away from the interrogation unit and a Raman pump is used to remotely power the switch. Furthermore, the deployed BOTDA unit uses an alternative configuration that can lead to simplified setups.
Open Access
Distributed humidity sensor for moisture-front monitoring in soils
(Optica, 2020) Leandro González, Daniel; Delgado Zabala, Oihane; López Rodríguez, José Javier; Bravo Acha, Mikel; López-Amo Sáinz, Manuel; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación
In this contribution, high spatial resolution distributed humidity sensing was demonstrated for moisture-front monitoring in soils by using polyimide coated optical fiber.
Open Access
Micro-drilled optical fiber for enhanced laser strain sensors
(SPIE, 2019) Pérez Herrera, Rosa Ana; Bravo Acha, Mikel; Roldán Varona, Pablo; Leandro González, Daniel; Rodríguez Cobo, Luis; López Higuera, José Miguel; López-Amo Sáinz, Manuel; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación
In this work, we present an experimental measurement of temperature and strain sensitivities of a micro-drilled optical fiber (MDOF). The MDOF consisted of a quasi-randomly distributed reflector along a single mode fiber (SMF). A fiber cavity laser based on MDOF was experimentally studied, attaining a single-wavelength laser emission centered at 1568.6nm. The output power level obtained from this single-laser oscillation when pumped at 140mW was around - 9.6dBm, and an optical signal to noise ratio (OSNR) of around 45dB was measured. Although temperature sensitivities of fiber Bragg gratings used as sensors are similar to our MDOF, strain sensitivity is enhanced around one order of magnitude when the MDOF was used.