Suchergebnisse

The international research community has been nurturing photonic technologies over the years, aiming to develop cost effective solutions for a number of applications. Optical fibers offer an efficient solution for sensing and communication fields. Fiber optic sensors present appealing characteristics that make them very attractive when compared with conventional electric sensors such as immunity to electromagnetic interferences, as well as unfavorable environments, small size, ability for multiplexing and remote sensing. Another important aspect when using optical fibers is the ability to simultaneously use them as sensors and communication channels. The primary motivation for this PhD work was the study and development of new structures based in photonic crystal fibers. The main idea was to take advantage of the know-how of our group in fiber-optic communications and photonic sensing, as well as the recent advances in the sensing area to develop new structures based on the platform of photonic crystal fibers. ; The work presented in this thesis was accomplished due to different financial supports, as well as co-work relationships inside of the university and outside during research times developed abroad. Due to the financial support obtained, thanks should be pay to: Spanish Government project TEC 2013-47264-C2-2-R; Innocampus and the INTERREG SUDOE Project "ECOAL-MGT-Ecological Management of Coal Waste Piles, SOE3/P2/P714"; As well as FEDER founds; Spanish Government project TEC 2016-76021-C2-1-R; Cost action MP1401; ; Programa de Doctorado en Tecnologías de las Comunicaciones, Bioingeniería y de las Energías Renovables (RD 99/2011) ; Bioingeniaritzako eta Komunikazioen eta Energia Berriztagarrien Teknologietako Doktoretza Programa (ED 99/2011)

In this paper, a new sensor system for simultaneous and quasi-independent strain and temperature measurements is presented. The interrogation of the sensing head has been carried out by monitoring the FFT phase variations of two of the microstructured optical fiber (MOF) cavity interference frequencies. This method is independent of the signal amplitude and also avoids the need to track the wavelength evolution in the spectrum, which can be a handicap when there are multiple interference frequency components with different sensitivities. The sensor is operated within a range of temperature of 30°C-75°C, and 380µɛ of maximum strain were applied; being the sensitivities achieved of 127.5pm/°C and -19.1pm/µɛ respectively. Because the system uses an optical interrogator as unique active element, the system presents a cost-effective feature. ; Financial support from the Spanish Comisión Interministerial de Ciencia y Tecnología within projects TEC2016-76021- C2-1-R, TEC2013-47264-C2-2-R and SUDOE ECOAL-MGT and FEDER funds from the European Union is acknowledged.

In this paper, a new sensor system for simultaneous and independent multipoint strain and temperature measurements is presented. The interrogation of the sensing heads has been carried out by monitoring their FFT phase variations. In particular, two of each microstructured optical fiber (M0F) cavity interference frequencies were used for the measures. This method is independent of the signal amplitude and also avoids the necessity of tracking the wavelength evolution in the spectrum, which can be a handicap when there are multiple interference frequency components with different sensitivities. The sensing heads present birefringent and multimodal properties and therefore both characteristics lead to their own interference with different properties and sensitivities. The multiplexing capability of the sensing heads and the interrogator method has also been tested and validated. Sensors were operated within a range of temperature 30°C-80°C and a deformation of ̴450 με was applied. Crosstalk between measurements can be corrected through simple math operations leading to independent and crosstalk-free multipoint and multiparameter sensors. ; This work was supported in part by the Spanish Comisi´on Interministerial de Ciencia y Tecnolog´ıa within projects TEC2016-76021-C2-1-R and TEC2013-47264-C2-2-R, in part by Cost action MP1401, and in part by FEDER funds from the European Union.

Two interrogation techniques for plasmonic tilted fiber Bragg grating sensors are reported and experimentally tested. Typical interrogation methods are usually based on tracking the wavelength shift of the most sensitive cladding mode, but for biosensing applications, spectrometer-based methods can be replaced by more efficient solutions. The proposed techniques thus rely on the measurement of the induced changes in optical power. The first one consists of a properly polarized tunable laser source set to emit at the wavelength of the sensor most sensitive mode and an optical power meter to measure the transmitted response. For the second method, a uniform fiber Bragg grating is photo-inscribed beyond the sensor in such a way that its central wavelength matches the sensor most sensitive mode, acting as an optical filter. Using a LED source, light reflected backwards by this grating is partially attenuated when passing through the sensor due to plasmon wave excitation and the power changes are quantified once again with an optical power meter. A performance analysis of the techniques is carried out and they both result competitive interrogation solutions. The work thus focuses on the development of cost-effective alternatives for monitoring this kind of biosensors in practical situations. ; Á. González-Vila is supported by the F.R.S.-FNRS through a FRIA grant. C. Caucheteur is supported by the F.R.S.- FNRS. The authors would also like to thank the financial support from the ERC (European Research Council) Starting Independent Grant PROSPER (grant agreement No. 280161 – http://www.umons.ac.be/erc-prosper), from the Spanish Comisión Interministerial de Ciencia y Tecnología within projects TEC2016-76021-C2-1-R and TEC2013-47264-C2-2- R and from SUDOE ECOAL-MGT and FEDER funds from the European Union.

In this paper, we present the results of a new pH sensor based on a polyaniline (PAni) coating on the surface of a tilted fiber Bragg grating. The pH-sensitive PAni was deposited by in situ chemical oxidative polymerization. The performance of the fabricated pH sensor was tested and the obtained pH values were compared with the results obtained using a pH meter device. It was found that the sensor exhibits response to pH changes in the range of 2-12, achieving a sensitivity of 46 pm/pH with a maximum error due to the hysteresis effect of ±1.14 pH. The main advantages of this PAni-TFBG pH sensor are biochemical compatibility, temperature independence, long-term stability and remote real-time multipoint sensing features. This type of sensor could be used for biochemical applications, pipeline corrosion monitoring or remote-multipoint measurements. ; Á. González-Vila is supported by the F.R.S.-FNRS through a FRIA grant. C. Caucheteur is supported by the F.R.S.- FNRS. The authors would also like to thank the financial support from the ERC (European Research Council) Starting Independent Grant PROSPER (grant agreement No. 280161 – http://www.umons.ac.be/erc-prosper), from the Spanish Comisión Interministerial de Ciencia y Tecnología within projects TEC2016-76021-C2-1-R and TEC2013-47264-C2-2- R and from SUDOE ECOAL-MGT and FEDER funds from the European Union. The authors also acknowledge the financial support of CAPTINDOOR WBGREEN programs (Walloon Region of Belgium).

This paper presents a new sensor system for vibration and relative humidity measurements based on its interaction with the evanescent field of a microwire. The interrogation of the sensing head is carried out by monitoring the fast Fourier transform (FFT) phase of one of the FFT peaks of the microwire transmission signal. This technique is not dependent of the signal amplitude and also eludes the requisite of tracking the wavelength evolution in the spectrum, which can be a handicap when there are multiple interference frequency components with different sensitivities. The point sensor is able to measure a wide humidity range (20%-70% relative humidity) with a maximum sensitivity reached of 0.14πrad/% relative humidity. This microwire sensor is also operated within a frequency range from 320 to 1300 Hz with a sensitivity of around 0.0051 nm -1 /Hz. Finally, due to the system uses an optical interrogator as unique active element, the system presents a cost-effective feature. ; This work was supported in part by the Spanish Comision Interministerial de Ciencia y Tecnología within project TEC2013-47264-C2-2-R and SUDOE ECOAL-MGT and FEDER funds from the European Union.

In this paper, the influence of the thickness of metallic-oxide coatings, ITO, and SnO2 on the sensitivity of a microstructured optical fiber Fabry–Pérot (FP) has been studied with the aim of developing ammonia gas fiber optic sensors. Also, the distribution of the optical power that can be coupled to the metallic-oxide sensing films is investigated in order to understand how the sensor's sensitivity can be improved; the thickness of the coatings plays a relevant role on the sensitivity and response time. Films with thicknesses between 200 and 850 nm were experimentally examined resulting in an optimal thickness of 625 nm for a SnO2 film. The behavior of the sensors toward different concentrations of ammonia gas from 10 to 130 ppm was analyzed by measuring the phase shifts of the reflected signal using the fast Fourier transform of its optical spectrum. The registered response/recovery times of this sensor are below 90 s. ; This work was supported in part by the Ministerio de Economía y Ciencia (MINECO) of Spain within projects under Grant TEC2016-79367-C2-2-R and Grant TEC2016-76021-C2-1-R, in part by the FEDER funds from the European Union, and in part by the University Public of Navarre Program Ph.D grants

This paper presents a new sensor system for vibration and relative humidity measurements based on its interaction with the evanescent field of a microwire. The interrogation of the sensing head is carried out by monitoring the fast Fourier transform (FFT) phase of one of the FFT peaks of the microwire transmission signal. This technique is not dependent of the signal amplitude and also eludes the requisite of tracking the wavelength evolution in the spectrum, which can be a handicap when there are multiple interference frequency . ; This work was supported in part by the Spanish Comisión Interministerial de Ciencia y Tecnología within project TEC2013-47264-C2-2-R and SUDOE ECOAL-MGT and FEDER funds from the European Union.

In this paper, a new optical fiber sensor for relative humidity measurements is presented and characterized. The sensor is based on a SnO2 sputtering deposition on a microstructured optical fiber (MOF) low-finesse Fabry-Pérot (FP) sensing head. The feasibility of the device as a breathing sensor is also experimentally demonstrated. The interrogation of the sensing head is carried out by monitoring the Fast Fourier Transform phase variations of the FP interference frequency. This method substitutes the necessity of tracking the optical spectrum peaks or valleys, which can be a handicap when noise or multiple contributions are present: therefore, it is low-sensitive to noise and to artifacts signal amplitude. The sensor shows a linear behavior in a wide relative humidity range (20%–90% relative humidity) in which the sensitivity is 0.14 rad/%; the maximum observed instability is 0.007 rad, whereas the highest hysteresis is 5% RH. The cross correlation with temperature is also considered and a method to lower its influence is proposed. For human breathing measurement, the registered rising and recovery times are 370 ms and 380 ms respectively. ; The authors are grateful to A. Ortigosa, D. Erro, Dr. M. Bravo and Dr. R.A. Perez-Herrera. We also thank the Spanish Government projects TEC2013-47264-C2-2-R, TEC 2016-76021-C2-1-R, TEC2016-78047-R, TEC2016-79367-C2-2-R, Innocampus and the Cost Action MP 1401, as well as to the AEI/FEDER Funds.

In this paper, a multiplexing system for simultaneous interrogation of optical fiber sensors which measure different parameters is presented and validated. The whole system has been tested with 6 different sensing heads with different purposes: one temperature sensing head, two relative humidity sensors and three VOCs leak sensors; all of them based on microstructured optical fibers. The interrogation system uses the FFT technique to isolate each sensor's interference, enabling their simultaneous interrogation. The system interrogates all the sensors at frequencies up to 1 KHz, showing a good performance of each measurement without crosstalk between sensors. The developed system is independent of the sensors' purpose or of the multiplexing topology. ; This work was supported in part by the Spanish Comisión Interministerial de Ciencia y Tecnología within projects under Grant TEC2016-76021-C2-1-R, Grant TEC2016-78047-R, and Grant TEC2016-79367-C2-2-R, in part by the Cost Action MP1401, and in part by the FEDER funds from the European Union.

In this paper, a new multipoint optical fiber system for relative humidity measurements based on Sn02-FP (Fabry-Pérot) sensing heads and an optical interrogator as single active device is presented and characterized. The interrogation of the sensing heads is carried out by monitoring the Fast Fourier Transform phase variations of the FP (Fabry-Pérot) interference frequencies. This method allows to multiplex several sensors with different wavelength spacing interference pattern. The sensors operate within a wide humidity range (20%-90% relative humidity) with low crosstalk between them. Five sensing heads have been measured using two different channels of the optical interrogator. The availability of four channels in the interrogator allows to multiplex a higher number of sensors, reducing proportionally the cost of each sensing point. ; The authors thank the Spanish Government projects TEC 2013-47264-C2-2-R, TEC2016-76021-C2-1-R, TEC2013- 43679-R Innocampus and the INTERREG SUDOE Project SOE3/P2/P714 as well as to the FEDER Funds.

A hybrid Fabry-Pérot cavity sensing head based on a four-bridge microstructured fiber is characterized for temperature sensing. The characterization of this cavity is performed numerically and experimentally in the L-band. The sensing head output signal presents a linear variation with temperature changes, showing a sensitivity of 12.5 pm/°C. Moreover, this Fabry-Pérot cavity exhibits good sensitivity to polarization changes and high stability over time. ; The authors are grateful to the Spanish Government projects TEC 2013-47264-C2-2-R, Innocampus and the INTERREG SUDOE Project "ECOAL-MGT—Ecological Management of Coal Waste Piles, SOE3/P2/P714", as well as to the FEDER Funds.

Trabajo presentado a la 26th International Conference on Optical Fiber Sensors. Suiza, 2019 ; A discrete sensor based on a Sn0₂-FP (Fabry-Pérot) cavity is presented and characterized in real soil conditions. Results are compared, for the first time to our knowledge, with a commercial capacitive sensor and gravimetric measurements. ; The Spanish Government projects TEC 2016-76021-C2-1-R, TEC2016-78047-R, TEC2016-79367-C2-2-R, Innocampus and the Cost Action MP 1401, as well as to the AEI/FEDER Funds are acknowledged.

Soil moisture content has always been an important parameter to control because it is a deterministic factor for site-specific irrigation, seeding, transplanting, and compaction detection. In this work, a discrete sensor that is based on a SnO2–FP (Fabry-Pérot) cavity is presented and characterized in real soil conditions. As far as authors know, it is the first time that a microstructured optical fiber is used for real soil moisture measurements. Its performance is compared with a commercial capacitive soil moisture sensor in two different soil scenarios for two weeks. The optical sensor shows a great agreement with capacitive sensor's response and gravimetric measurements, as well as a fast and reversible response; moreover, the interrogation technique allows for several sensors to be potentially multiplexed, which offers the possibility of local measurements instead of volumetric: it constitutes a great tool for real soil moisture monitoring. ; This work was supported by the Spanish Government projects TEC2016-76021-C2-1-R, TEC2016-78047-R, TEC2016-79367-C2-2-R, Innocampus and the Cost Action MP 1401, as well as to the AEI/FEDER Funds.

In this paper, a new sensor system for relative humidity measurements based on a SnO2 sputtering deposition on a microstructured optical fiber (MOF) low-finesse Fabry-Pérot (FP) sensing head is presented and characterized. The interrogation of the sensing head is carried out by monitoring the Fast Fourier Transform phase variations of the FP interference frequency. This method is low-sensitive to signal amplitude variations and also avoids the necessity of tracking the evolution of peaks and valleys in the spectrum. The sensor is operated within a wide humidity range (20%-90% relative humidity) with a maximum sensitivity achieved of 0.14rad/%. The measurement method uses a commercial optical interrogator as the only active element, this compact solution allows real time analysis of the data. ; We also thank the Spanish Government projects TEC 2013-47264-C2-2-R, TEC2013-43679-R Innocampus and the INTERREG SUDOE Project SOE3/P2/P714 as well as to the FEDER Funds.