Interferómetro de fibra óptica de tres brazos : Aplicación para el desarrolllo de un sensor de presión

En este trabajo hemos estudiado los dispositivos interferométricos en fibra óptica y en concreto un interferómetro de tres brazos. Hemos desarrollado este dispositivo y estudiado su aplicación como sensor de dos magnitudes externas que actúan simultáneamente sobre uno de los brazos sensor. También hemos estudiado su aplicación como sensor de presión, realizándose medidas que cubren el rango 0-20 kg/cm2. En todas las pruebas realizadas se ha comprobado la linealidad del sistema de detección escogido

Surface plasmon resonance sensors based on uniform-waist tapered fibers in a reflective configuration

We present a configuration for surface plasmon resonance sensors based on uniform-waist tapered optical fibers and reflective elements. Once the fiber is tapered fulfilling the adiabatic criterion, a multilayer including a metallic medium is asymmetrically deposited on the uniform waist of the fiber. This feature provides the resonant excitation of multiple surface plasma waves. In addition, a mirror is produced at the fiber tip by a chemical Tollens reaction. In this way, the sensor operates in a reflective mode, more convenient for dip probes. When these sensors are spectrally interrogated, a high sensitivity of 10^4 refractive index units per nanometer is attained. These devices can be advantageously used for any kind of chemical sensing and biosensing

Theoretical method for the study of plasmon generation in hybrid multilayer-optical fiber structures

A theoretical method is presented for the determination of the behavior of devices based on the deposition of multilayer structures on polished optical fibers. Plasmon generation in metallic layers is modeled. The method is based on the Rayleigh expansion of the electric fields and permits us to determine their distribution over the whole structure by an application of boundary conditions. Once the distribution is known, the power transmitted by the fiber can be computed as a function of the geometrical and refractive parameters of the device. The method is versatile and can be used as a theoretical tool for the design of devices of that type used for many different purposes. We present real experimental results obtained with an operative sensor that agree with the theoretical predictions of our technique and prove its suitability

Despertando la curiosidad científica en infantil a través de la colaboración de familia, escuela y centro universitario

The experience presented is an activity for preschool students. The aim is to arouse their scientific curiosity and encourage collaboration among members of the educational community by participating students' parents, and students and teachers from the Teacher Training College ‘Sagrada Familia’ in Úbeda. The experience consisted of a day of workshops for preschool students from the state school "San Ginés de la Jara" in Sabiote (Jaén). In those workshops the students discovered scientific phenomena through experiments. A total of four workshops were carried out. They were based on scientific methodology in which children first observe, then formulate hypotheses, check the phenomenon and, finally, draw a conclusion. To study the initiation to scientific curiosity in the group of children we used the qualitative technique of text production. Also, as the experience was designed as a training project through the collaborative work of several sectors of the community, we decided to study the evolution in the correlation between theory and practice that trainee teachers had by means of a pretest-posttest research design with a single group, on the basis of a questionnaire on solving problematic scientific situations. In the same way, we used a pretest-posttest design based on a questionnaire with open-ended questions to analyze whether the family context was a collaborative environment to foster scientific curiosity and to contribute to its development in a setting other than the school. The results show that, after the intervention, a significant group of children remind one or more of the experiments of the workshops and are able to give a scientific explanation of them. The information drawn from the data collected in the family setting expand the results mentioned before, since it shows that, in some homes, children have applied scientific knowledge and, thus, the family context has become a collaborative environment to encourage scientific curiosity. Besides, the analysis of the data collected from trainee teachers show that most of them are capable of linking theory and practice after the experience. Key words: Scientific methodology, collaborative work, scientific curiosity, initial training, permanent training.La experiencia se plantea como una actividad para el alumnado de Educación Infantil. El fin es despertar la curiosidad científica y fomentar la colaboración entre los miembros de la comunidad educativa al participar padres y madres del alumnado, estudiantes de Educación Infantil y profesores de la Escuela Universitaria. El desarrollo de la experiencia se basó en la organización de una jornada de talleres para el alumnado de segundo ciclo de Educación Infantil del CEIP “San Ginés de la Jara”, de Sabiote (Jaén), en los que se presentaba el descubrimiento de fenómenos científicos a través de experimentos, con la colaboración de los padres y madres interesados en el proyecto y del alumnado de Magisterio de la Escuela Universitaria de Magisterio “Sagrada Familia”, de Úbeda, cercana al centro en el que se desarrolló la experiencia. Se realizaron un total de cuatro talleres basados en una metodología científica, dejando a los niños que observaran en primer lugar, lanzaran hipótesis, comprobaran el fenómeno sobre el que estaban haciendo las conjeturas y, finalmente, extrajeran una conclusión. Para estudiar la iniciación a la curiosidad científica en el grupo de niños y niñas de infantil utilizamos la técnica cualitativa de producción de textos. Asimismo, como la experiencia se preparó como un proyecto de formación a través del trabajo colaborativo de varios sectores de la comunidad, nos propusimos estudiar la evolución en la interrelación de teoría y práctica entre el alumnado de magisterio a través de un diseño de investigación de un sólo grupo con pretest-postest y a partir de un cuestionario de resolución de situaciones científicas problemáticas. De manera similar, para analizar si el contexto familiar constituía un entorno de colaboración para alentar la curiosidad científica y contribuir desde otro ambiente diferente al escolar a su desarrollo, utilizamos un diseño pretest-postest a partir de un cuestionario de preguntas abiertas

Simple model of compound waveguide structures used as fiber-optic sensors

In this work we present an application of a simple quasi-geometrical model to analyze the behavior of compound waveguide structures used as fiber-optic sensors. This theoretical model is based on the adjustment of the parameters of the structure from the experimental measures to predict the observed behavior of the device. It also takes into account the non-monocromaticity of the used source. In this way, it can be used as a design criterion for this kind of structures. It is applied to a refractive index fiber-optic sensor based on the excitation of surface plasmon in a metal layer by the light guided by a monomode fiber

A fibre-optic temperature sensor based on the deposition of a thermochromic material on an adiabatic taper

A fibre-optic sensor has been developed for the measurement of temperature, especially of liquids. The device is conceived as part of an all-optical CTD probe for the control of the physical parameters of a marine medium. The dependence on temperature of the optical properties (specifically, absorbance) of a thermochromic material, namely lophine (2,4,5-triphenylimidazole), is the basis of the sensor. The sensor presents some significant differences with respect to other similar sensors proposed in the literature: the use of adiabatic, long, tapered optical fibres with adjustable geometric parameters; the use of LED illumination in the 800 nm range; improvements in the deposition technique, etc. The sensors show a linear behaviour over the desired temperature range, and their sensitivity is high. Also, the dependence of the response of the sensor with variations of the geometry of the tapers is discussed. Specifically, we have performed measurements with different diameters of the taper waist, and we show the dependence of the slope of the response curve with that parameter

Surface plasmon resonance in the visible region in sensors based on tapered optical fibers

Doubly deposited uniform-waist tapered optical fibers (DLUWTs) have shown their versatility and good performance as basis for surface plasmon resonance (SPR) sensors for a variety of wavelength ranges. In this work we experimentally show how these devices can be employed to extend the technology of SPR fiber sensors to the visible region, down to about 530 nm, with remarkable results in terms of sensitivity, plasmon definition and the availability of multiple plasmon resonances for each configuration. In this way, DLUWTs can be used to cover a range of more than 1000 nm for aqueous media only by changing the thickness of the deposits. Also, it is shown how these results can be used with the so-called absorption method to make selective the response of the sensors and a study is made on the influence of the taper waist in the performance of the devices. The number of SPR fiber sensors working in the visible region, of great interest in biological research, that have been depicted in the literature is very small, and the sensors that we present here notably improve their performance

Ellipsometric characterization of Bi and Al2O3 coatings for plasmon excitation in an optical fiber sensor

The authors present the results of the ellipsometric characterization of thin layers of bismuth and aluminum oxide deposited over the waist of a tapered optical fiber by pulsed laser deposition. The characteristics of the deposits are studied by spectroscopic ellipsometry. From the effective thicknesses determined by the ellipsometric characterization, it is shown by simulations that surface plasmon resonances (SPRs) can occur in the fiber device, and it is demonstrated experimentally. These results show the feasibility of employing bismuth as a plasmonic material in SPR fiber sensors based on doubly-deposited uniform-waist tapered optical fibers, which show excellent performance and versatility

Surface plasmon excitation in fiber-optics sensors: a novel theoretical approach.

A theoretical method for the study of surface plasmon excitation in metallic layers, as used in fiber-optics sensors, is presented. It is based in the calculation of the propagated fields in the waveguide structure and allows us to compute the loss of optical power in the fiber (which is the measured parameter) from energy conservation considerations. The agreement with experimental data obtained with real sensors is good. The method is conceptually simple and can be adapted to different configurations of the sensors

Despertando la curiosidad científica en infantil a través de la colaboración de familia, escuela y centro universitario

L’experiència es planteja com una activitat per a l’alumnat d’Educació Infantil. La fi és despertar la curiositat científica i fomentar la col·laboració entre els membres de la comunitat educativa pel fet que hi participen pares i mares de l’alumnat, estudiants d’Educació Infantil i professors de l’Escola Universitària. El desenvolupament de l’experiència es va basar en l’organització d’una jornada de tallers per a l’alumnat de segon cicle d’Educació Infantil del CEIP «Sant Ginés de la Jara», de Sabiote (Jaén), en els quals es presentava el descobriment de fenòmens científics a través d’experiments, amb la col·laboració dels pares i mares interessats en el projecte i de l’alumnat de Magisteri de l’Escola Universitària de Magisteri «Sagrada Família», d’Úbeda, propera al centre en el qual es va desenvolupar l’experiència. Es van dur a terme un total de quatre tallers basats en una metodologia científica, deixant als nens que observessin en primer lloc, fessin hipòtesis, comprovessin el fenomen sobre el qual estaven fent les conjectures i, finalment, extraguessin una conclusió. Per estudiar la iniciació a la curiositat científica en el grup de nens i nenes d’infantil utilitzem la tècnica qualitativa de producció de textos. Així mateix, com l’experiència es va preparar com un projecte de formació a través del treball col·laboratiu de diversos sectors de la comunitat, ens vam proposar estudiar l’evolució en la interrelació de teoria i pràctica entre l’alumnat de magisteri a través d’un disseny d’investigació d’un sol grup amb pretest-postest i a partir d’un qüestionari de resolució de situacions científiques problemàtiques. De manera similar, per analitzar si el context familiar constituïa un entorn de col·laboració per encoratjar la curiositat científica i contribuir des d’un altre ambient diferent a l’escolar al seu desenvolupament, utilitzem un disseny pretest-postest a partir d’un qüestionari de preguntes obertes.The experience presented is an activity for preschool students. The aim is to arouse their scientific curiosity and encourage collaboration among members of the educational community by participating students' parents, and students and teachers from the Teacher Training College ‘Sagrada Familia’ in Úbeda. The experience consisted of a day of workshops for preschool students from the state school "San Ginés de la Jara" in Sabiote (Jaén). In those workshops the students discovered scientific phenomena through experiments. A total of four workshops were carried out. They were based on scientific methodology in which children first observe, then formulate hypotheses, check the phenomenon and, finally, draw a conclusion. To study the initiation to scientific curiosity in the group of children we used the qualitative technique of text production. Also, as the experience was designed as a training project through the collaborative work of several sectors of the community, we decided to study the evolution in the correlation between theory and practice that trainee teachers had by means of a pretest-posttest research design with a single group, on the basis of a questionnaire on solving problematic scientific situations. In the same way, we used a pretest-posttest design based on a questionnaire with open-ended questions to analyze whether the family context was a collaborative environment to foster scientific curiosity and to contribute to its development in a setting other than the school. The results show that, after the intervention, a significant group of children remind one or more of the experiments of the workshops and are able to give a scientific explanation of them. The information drawn from the data collected in the family setting expand the results mentioned before, since it shows that, in some homes, children have applied scientific knowledge and, thus, the family context has become a collaborative environment to encourage scientific curiosity. Besides, the analysis of the data collected from trainee teachers show that most of them are capable of linking theory and practice after the experience.La experiencia se plantea como una actividad para el alumnado de Educación Infantil. El fin es despertar la curiosidad científica y fomentar la colaboración entre los miembros de la comunidad educativa al participar padres y madres del alumnado, estudiantes de Educación Infantil y profesores de la Escuela Universitaria. El desarrollo de la experiencia se basó en la organización de una jornada de talleres para el alumnado de segundo ciclo de Educación Infantil del CEIP “San Ginés de la Jara”, de Sabiote (Jaén), en los que se presentaba el descubrimiento de fenómenos científicos a través de experimentos, con la colaboración de los padres y madres interesados en el proyecto y del alumnado de Magisterio de la Escuela Universitaria de Magisterio “Sagrada Familia”, de Úbeda, cercana al centro en el que se desarrolló la experiencia. Se realizaron un total de cuatro talleres basados en una metodología científica, dejando a los niños que observaran en primer lugar, lanzaran hipótesis, comprobaran el fenómeno sobre el que estaban haciendo las conjeturas y, finalmente, extrajeran una conclusión. Para estudiar la iniciación a la curiosidad científica en el grupo de niños y niñas de infantil utilizamos la técnica cualitativa de producción de textos. Asimismo, como la experiencia se preparó como un proyecto de formación a través del trabajo colaborativo de varios sectores de la comunidad, nos propusimos estudiar la evolución en la interrelación de teoría y práctica entre el alumnado de magisterio a través de un diseño de investigación de un sólo grupo con pretest-postest y a partir de un cuestionario de resolución de situaciones científicas problemáticas. De manera similar, para analizar si el contexto familiar constituía un entorno de colaboración para alentar la curiosidad científica y contribuir desde otro ambiente diferente al escolar a su desarrollo, utilizamos un diseño pretest-postest a partir de un cuestionario de preguntas abiertas.Los resultados muestran que, tras la intervención, un grupo significativo de niños y niñas recuerdan uno o varios de los experimentos de los talleres y son capaces de dar una explicación científica de los mismos. La información que arrojan los datos extraídos en el ámbito familiar amplían los resultados anteriores, puesto que ponen de manifiesto que, en algunos hogares, los niños han aplicado los conocimientos científicos y, de esta manera, el contexto familiar se ha constituido en un entorno de colaboración que alenta la curiosidad científica. Por su parte, los resultados del alumnado de Magisterio indican que la mayoría es capaz de interrelacionar teoría y práctica después de la experiencia