Showing papers by "Ignacio R. Matias published in 2014"

Optical fiber refractometers based on Lossy Mode Resonances by means of SnO2 sputtered coatings

Abstract: The fabrication of optical fiber refractometers by means of the deposition of a thin tin-dioxide coating onto an optical fiber core is presented. Tin-dioxide permits the guided light in the fiber to be coupled from its core to its coating, creating lossy mode resonances in the infrared and visible regions. These resonances vary as a function of the external medium's refractive index, enabling the fabrication of robust and highly reproducible wavelength-based optical fiber refractometers. Moreover, the first seven lossy modes create seven differentiated resonances which have been studied in the range between 450 and 1650 nm of the optical spectrum. The central wavelength of the resonances can be adjusted by varying the thickness of the tin-dioxide coating.

Spectral width reduction in lossy mode resonance-based sensors by means of tapered optical fibre structures

Abstract: This contribution pursues the goal of achieving an optical fibre-based platform to detect anti-gliadin antibodies (AGAs), in order to early diagnose celiac disease. To this purpose, the generation of lossy mode resonances (LMRs) in several evanescent field optical structures was studied both theoretically and experimentally. LMRs were obtained by adsorbing a polymeric thin-film onto the optical structures using the layer-by-layer assembly technique. The LMR shape depends on the geometry of the optical structure and its attenuation was controlled just by tuning the length of the device. The best performance was obtained with tapered single-mode optical fibres, which provided more than a 50% reduction in the spectral width of the LMR by using a shorter device. This improvement was successfully applied to detect anti-gliadin antibodies (AGAs) in 5 ppm concentration, what can be used to diagnose celiac disease, and shows the potential of this technology to address biosensing applications.

A Fiber Optic Ammonia Sensor Using a Universal pH Indicator

Abstract: A universal pH indicator is used to fabricate a fiber optic ammonia sensor. The advantage of this pH indicator is that it exhibits sensitivity to ammonia over a broad wavelength range. This provides a differential response, with a valley around 500 nm and a peak around 650 nm, which allows us to perform ratiometric measurements. The ratiometric measurements provide not only an enhanced signal, but can also eliminate any external disturbance due to humidity or temperature fluctuations. In addition, the indicator is embedded in a hydrophobic and gas permeable polyurethane film named Tecoflex®. The film provides additional advantages to the sensor, such as operation in dry environments, efficient transport of the element to be measured to the sensitive area of the sensor, and prevent leakage or detachment of the indicator. The combination of the universal pH indicator and Tecoflex® film provides a reliable and robust fiber optic ammonia sensor.

Sensitivity enhancement in a multimode interference-based SMS fibre structure coated with a thin-film: Theoretical and experimental study

Abstract: Multimode interference in a single-mode–multimode–single-mode (SMS) fibre structure leads to the generation of transmission bands and attenuation bands in the optical spectrum. In this work, the progressive deposition, with layer-by-layer assembly technique, of a high refractive index thin-film onto the SMS structure permits to observe the evolution of the bands as a function of the coating thickness. The results show that it is possible to increase the sensitivity of the device to variations of the coating thickness, what indicates the adequateness of this structure as a sensing platform. The experimental results are corroborated with a numerical method based on coupled-mode theory. As a practical application, a sensitivity improvement has been obtained a pH sensor by increasing the coating thickness.

Refractometric sensors based on multimode interference in a thin-film coated single-mode–multimode–single-mode structure with reflection configuration

Abstract: Thin-film coated single-mode-multimode-single-mode (SMS) structures have been analyzed both theoretically and experimentally with the aim of detecting different refractive indices. By adequate selection of the thickness of the thin film and of the diameter of the multimode segment in the SMS structure, a seven-fold improvement can be obtained in the sensitivity of the device to the surrounding medium refractive index, achieving a maximum sensitivity of 1199.18 nm/refractive index unit for the range of refractive indices from 1.321 to 1.382. Using layer-by-layer self-assembly for deposition, both on the cladding and on the tip of the multimode segment, allows the reflected power to increase, which avoids the application of a mirror on the tip of the multimode segment.

Analysis Matrix for Smart Cities

Abstract: The current digital revolution has ignited the evolution of communications grids and the development of new schemes for productive systems. Traditional technologic scenarios have been challenged, and Smart Cities have become the basis for urban competitiveness. The citizen is the one who has the power to set new scenarios, and that is why a definition of the way people interact with their cities is needed, as is commented in the first part of the article. At the same time, a lack of clarity has been detected in the way of describing what Smart Cities are, and the second part will try to set the basis for that. For all before, the information and communication technologies that manage and transform 21st century cities must be reviewed, analyzing their impact on new social behaviors that shape the spaces and means of communication, as is posed in the experimental section, setting the basis for an analysis matrix to score the different elements that affect a Smart City environment. So, as the better way to evaluate what a Smart City is, there is a need for a tool to score the different technologies on the basis of their usefulness and consequences, considering the impact of each application. For all of that, the final section describes the main objective of this article in practical scenarios, considering how the technologies are used by citizens, who must be the main concern of all urban development.

A comparative study of two different approaches for the incorporation of silver nanoparticles into layer-by-layer films

Abstract: In this work, a comparative study about the incorporation of silver nanoparticles (AgNPs) into thin films is presented using two alternative methods, the in situ synthesis process and the layer-by-layer embedding deposition technique. The influence of several parameters such as color of the films, thickness evolution, thermal post-treatment, or distribution of the AgNPs along the coatings has been studied. Thermal post-treatment was used to induce the formation of hydrogel-like AgNPs-loaded thin films. Cross-sectional transmission electron microscopy micrographs, atomic force microscopy images, and UV-vis spectra reveal significant differences in the size and distribution of the AgNPs into the films as well as the maximal absorbance and wavelength position of the localized surface plasmon resonance absorption bands before and after thermal post-treatment. This work contributes for a better understanding of these two approaches for the incorporation of AgNPs into thin films using wet chemistry.

Gasohol Quality Control for Real Time Applications by Means of a Multimode Interference Fiber Sensor

Abstract: In this work we demonstrate efficient quality control of a variety of gasoline and ethanol (gasohol) blends using a multimode interference (MMI) fiber sensor. The operational principle relies on the fact that the addition of ethanol to the gasohol blend reduces the refractive index (RI) of the gasoline. Since MMI sensors are capable of detecting small RI changes, the ethanol content of the gasohol blend is easily determined by tracking the MMI peak wavelength response. Gasohol blends with ethanol contents ranging from 0% to 50% has been clearly identified using this device, which provides a linear response with a maximum sensitivity of 0.270 nm/% EtOH. The sensor can also distinguish when water incorporated in the blend has exceeded the maximum volume tolerated by the gasohol blend, which is responsible for phase separation of the ethanol and gasoline and could cause serious engine failures. Since the MMI sensor is straightforward to fabricate and does not require any special coating it is a cost effective solution for real time and in-situ monitoring of the quality of gasohol blends.

Improved multifrequency phase-modulation method that uses rectangular-wave signals to increase accuracy in luminescence spectroscopy.

Abstract: We propose a novel multifrequency phase-modulation method for luminescence spectroscopy that uses a rectangular-wave modulated excitation source with a short duty cycle. It is used for obtaining more detailed information about the luminescence system: the information provided by different harmonics allows estimating a model for describing the global frequency response of the luminescent system for a wide range of analyte concentration and frequencies. Additionally, the proposed method improves the accuracy in determination of the analyte concentration. This improvement is based on a simple algorithm that combines multifrequency information provided by the different harmonics of the rectangular-wave signal, which can be easily implemented in existing photoluminescence instruments by replacing the excitation light source (short duty cycle rectangular signal instead of sinusoidal signal) and performing appropriate digital signal processing after the transducer (implemented in software). These claims have bee...

Optical fiber humidity sensor based on a tapered fiber asymmetrically coated with indium tin oxide

Abstract: In this work a new humidity sensor based on lossy mode resonances (LMR) generated on a biconically tapered single mode optical fiber is presented. The tapered fiber was coated only on one side using indium tin oxide (ITO) by means of sputtering in order to generate the LMR. This asymmetrical structure (180 degrees of coating) makes the device sensitive to the polarization of the light so that the LMR can be separated in its TE and TM modes. The polarization dependence produces the effect of a smaller bandwidth in the LMR resonance with respect to the symmetrical coating, allowing a better resolution in the peak detection procedure. The sputtering process was carefully monitored in order to have the LMR placed in the range of measurement. Then the sensor was characterized using a climatic chamber with humidity in the range 20-80%RH. A sensitivity of 200 pm/%RH was obtained using a tapered fiber of 35 μm of waist diameter.

Optical fiber refractometers based on localized surface plasmon resonance (LSPR) and lossy mode resonance (LMR)

Abstract: An optical fiber device showing simultaneously two optical phenomena, localized surface plasmon resonance (LSPR) and lossy mode resonance (LMR), is presented here for the first time. It consists of a fragment of stripped optical fiber coated with a polymeric film that includes gold nanoparticles. The absorption peaks related to both phenomena were captured during the deposition of the coating, showing a different evolution. In addition, the behavior of both phenomena to variations of the surrounding medium refractive index (SMRI) was monitored, studying the different responses of LSPR and LMR.

University-industry collaboration chairs: Initiatives at the Public University of Navarre

Abstract: In the current context of economic crisis, the university Chairs funded by private companies emerge as useful tools to establish a steady and fruitful collaboration between universities and industry. The activities, configuration and management of the Chairs at the Public University of Navarre (UPNa) are described along the paper. The UPNa Chair for Renewable Energies is shown as a successful initiative, particularly concerning its Engineering Degree Final Project and Master Thesis Program.

Exhaled Breath Optical Fiber Sensor based on LMRs for Respiration Monitoring

Abstract: In this work, the fabrication and characterization of a small and portable exhaled breath sensor based on Lossy Mode Resonances (LMR) is presented. Tin oxide (SnO2) coatings fabricated onto optical fibers are used as LMR supporting coatings. The principle of operation is based on the measurement of refractive index changes by the LMR device (with an average sensitivity of 8355 nm/RIU) originated by the condensation of micro water droplets in the surroundings of the SnO2 coating during the breath natural process. The sensor shows a repetitive response with less than 100 ms of response time and a wavelength shift of 150 nm from inhalation to exhalation.

Optical fiber Bragg grating mesh for multiphase flow sensing

Abstract: This work introduces a new approach to characterize the multiphase flow by means of the utilization of optical fiber Bragg gratings. Here, the force applied by the air/liquid flow on the fiber gratings is the underlying mechanism of these sensors. Flow images are constructed from the response of a 8x8 mesh of sensors, with a total of 16 different FBGs multiplexed in wavelength. The data from each sensor has been processed in order to obtain a 2D plot of the air/liquid phase as well as a 3D plot of the air bubbles inside the tube for each time interval.

Analysis of women enrollment in Engineering programs at the Public University of Navarre

Abstract: Women represent more than 50% of the University students both in Europe and the United States. According to this, one might assume that the number of female students in Engineering might have been progressively increasing. But, the under-representation of women in engineering degrees has become a persistent problem. This work presents an analysis of women enrolment in engineering degrees at the Public University of Navarre, where a negative tendency has been detected over the past 10 years. In order to understand the underlying causes of this situation, a survey was conducted among students of all engineering programs. As a conclusion, some straightforward actions that could attract more women to technological studies are proposed.

D-shape optical fiber refractometer based on TM and TE lossy mode resonances

Abstract: The fabrication and characterization of an optical fiber refractometer based on Lossy Mode Resonances (LMR) is presented. TiO2/ poly (sodium 4-styrenesulfonate) coatings deposited on side-polished D-shaped optical fibers are used as LMR supporting coatings. LMRs are sensitive to the external medium refractive index and D-shaped optical fibers enable the observation of TE and TM LMR polarizations. These refractometers based on TE and TM LMR showed an average sensitivity of 2737 nm/RIU and 2893 nm/RIU respectively for a surrounding medium refractive index (SMRI) range from 1.35 to 1.41.

Optical fiber current transducer using lossy mode resonances for high voltage networks

Abstract: This work presents the development and characterization of an optical fiber current transducer based on lossy mode resonances (LMRs) to work in high voltage networks. A multilayer structure was created in order to be able to shift the LMR by an electro-optic material deposited in the middle of two electrodes. The optical resonance has a displacement range of 200 nm on its TM component, what makes this device suitable for current sensing. Furthermore, dip coating of polyvinylidene difluoride has enhanced the nanofilm uniformity with respect to previous devices.

Analysis of efficient dense wireless sensor network deployment in Smart City environments

Abstract: In this work, the massive deployment of wireless sensor networks inherent in the implementation of context aware Smart City environments is presented. A precise estimation considering the topology and the morphology of wide service areas, with a potential large density of transceivers is performed with the aid of in-house deterministic 3D ray launching algorithm, which is specifically adapted to the conditions of large volume and large traffic density. Due to the co-existence of multiple wireless systems (such as wireless local area networks, mobile networks, body area networks or RF proprietary systems), a heterogeneous scenario, in terms of traffic distribution and hence overall interference is present. The precise characterization of coverage areas of all wireless transceivers, as information sources or undesired interference sources, leads to optimal deployment configurations, in which interference levels are minimized, quality of service is enhanced and overall energetic consumption can be optimized.

Low voltage transducer based on the changes in the wavelength of the attenuation band

Abstract: In this work a fiber optic voltage transducer using oriented poly(vinylidene fluoride) (PVDF) films prepared by dip coating is presented. The device consists of an inner nanofilm of silver, an intermediate layer of PVdF and an external layer of Indium Tin Oxide (ITO). The metal layers were coated by sputtering, and they generate an electromagnetic resonance that produces an attenuation band, besides acting as electrodes. The fabricated transducer has demonstrated high sensitivity to the applied voltage showing wavelength displacements of up to 200 nm.

Optical fiber °Brix sensor based on Lossy Mode Resonances (LMRs)

Abstract: The fabrication and characterization of an optical fiber °Brix sensor based on Lossy Mode Resonances (LMRs) is presented. ITO coatings deposited on side-polished D-shaped optical fibers are used as LMR supporting coatings. LMRs are highly sensitive to external medium refractive index variations and enable an accurate determination of sugar concentration in the surroundings of the device by means of a LMR wavelength shift when the device is immersed in sugar based solution. The fabricated sensors have been used to measure sugar concentrations from 5% to 50%, which is within the requirements of most common applications. The response of the devices is linear with a linearity factor R2 0.9961 and a sensitivity of 11.8 nm/°Brix, which means a resolution of ~0.005 °Brix by using a conventional communications Optical Spectrum Analyzer (OSA). Presented device shows a twenty-fold improvement in sensitivity compared with comercial Brix refractometers.

Celiac disease biodetection using lossy-mode resonances generated in tapered single-mode optical fibers

Abstract: This work presents the development and test of an anti-gliadin antibodies biosensor based on lossy mode resonances (LMRs) to detect celiac disease. Several polyelectrolites were used to perform layer-by-layer assembly processes in order to generate the LMR and to fabricate a gliadin-embedded thin-film. The LMR shifted 20 nm when immersed in a 5 ppm anti-gliadin antibodies-PBS solution, what makes this bioprobe suitable for detecting celiac disease. This is the first time, to our knowledge, that LMRs are used to detect celiac disease and these results suppose promising prospects on the use of such phenomena as biological detectors.

Two-Phase Flow Imaging by means of an 8x8 Optical Fiber Bragg Grating Grid

Abstract: Two-phase flows characterization by means of the utilization of an optical fiber Bragg grating (FBG) grid is presented. The force applied by the air/liquid flow on the FBGs is the underlying mechanism of this sensor.

Fluid turbulence monitoring by means of FBG mesh

Abstract: Single-phase flow turbulence monitoring by means of the utilization of an optical fiber Bragg grating (FBG) mesh is presented in this work. Present device is immune to electromagnetic interferences and independent of the fluid dielectric constant or pipe transparency. The kinetic energy of the flow produces a wavelength shift associated to the strain, which is the basis of the detection mechanism. Spatial resolution inside the pipes is obtained by arranging the FBGs in a 8×8 matrix shape with a total of 16 FBGs multiplexed within the same single mode fiber (SMF), which reduces considerably the size and connections of the device. The results show differentiated patterns as a function of time and flow speed, which can be directly associated to velocity distributions inside the tube. Different regions can be differentiated as a function of the force induced strain: core, annular and wall regions.

Proposal for Improving Connectivity and adding Authentication and Security to KNXNet/IP Protocol

Abstract: KNXnet/IP protocol defines mechanisms for using KNX Home and Building Automation technology on top of the IP protocol using client/server architecture. Due the nature of KNXnet/IP protocol it presents some connectivity and security problems inherent to the protocol definition. In this work we propose some mechanisms for trying to fix these problems and finally we implement and test them using real KNX devices.

Engineering international programs at the public university of Navarre: A satisfactory on-going experience in a context of industrial globalization

Abstract: In a context of global industrialization, the engineers have to be not only competent and technically well-prepared but also show effective communication in other languages, preferably English, and intercultural skills. For an engineering degree to be competitive, their academic curriculum has to be designed taking into account this fact. This paper describes the Engineering International Programs at the School of Industrial and Telecommunications Engineering of the Public University of Navarre, and particularly how they are organized into two programs, namely the International Curriculum Program and the Student Mobility Program. Both Programs are described in terms of organization, management and admission requirements. Preliminary results of this work-in-progress experience, including number of students enrolled in the Programs and results of the students' satisfaction surveys, are very satisfactory and show the growing interest of students and teachers in the Programs and, more generally, in the internationalization of the academic curricula of the Engineering Degrees of the School.

Fiber Optic Sensors based on Lossy Mode Resonances

Abstract: An optical waveguide coated by a thin film affects the propagation of the light generating a type of resonances called lossy mode resonances (LMR), very interesting for sensing purposes.