Experimental test of polymer optical fiber temperature sensor on different surrounding media

The proceeding at: 22nd International Conference on Plastic Optical Fibers (POF 2013), took place in 2013 September,11-13, in Armação dos Buzios, Rio de Janeiro, (Brasil). The event Web site at: http://www.pof2013.org.br/ .Influence of external media on a fiber-optic temperature sensor based on a macro-bend multimode Polymer Optical Fiber (POF) is analyzed. The sensor has a linear response with a sensitivity of 〖1.92.10〗^(-3) 〖(°C) 〗^(-1) at a fixed bend radius. 2.4 times sensitivity variations for different surrounding media are reported.This work has been sponsored by the Ministerio de Economía y Competitividad (TEC2012-37983-C03-02) & (TEC2012-37983-C03-01), Ministerio de Educación, Cultura y Deportes (PRX12/00007) y Comunidad de Madrid FACTOTEM-2/2010/00068/001.Publicad

High-Sensitivity Fabry-Perot Temperature Sensor Based on Liquid Crystal Doped With Nanoparticles

The response of a Fabry-Perot interferometer filled with a nematic liquid crystal doped with silver nanoparticles is theoretically studied as a temperature sensor. It has been observed that the high dependence of the extraordinary refractive index of a liquid crystal along with the influence of the plasmonic resonances of nanoparticles produce useful phenomena for temperature sensing. Accordingly, we theoretically demonstrated the optical response of this device as a function of the temperature and the nanoparticles radius. The application of different technologies as optical sources was investigated through a simulation program. The latter enabled us to estimate the sensitivity and predict interesting parameters of the device, such as optimum wavelength ranges, for the optical sources or optimum sizes of the nanoparticles. Maximum sensitivities of 24 . 10(-2) dB/degrees C are obtained.This work was supported in part by the Ministerio de Ciencia e Innovación of Spain (grant no. TEC2013-47342-C2-2-R) and the Comunidad de Madrid (grant no. FACTOTEM2 S2009/ESP-1781).Publicad

Polymer Optical Fiber Temperature Sensor With Dual-Wavelength Compensation of Power Fluctuations

The design and development of a plastic optical fiber macrobend temperature sensor is presented. The sensor can operate in a temperature range from -55 to 70 degrees C and has a linear response versus temperature with a sensitivity of 8.95.10(-4) degrees C-1. The sensor system uses the ratio of transmittance at two wavelengths to implement a self-referencing technique in order to avoid undesirable power fluctuations influence. The transmittance ratio precision is 0.1%. An analysis has been developed to find the two wavelengths which ratio offers the highest linearity and sensitivity response. Experimental results are successfully compared with theoretical approaches.This work was supported by the Spanish Ministry of Economía y Competitividad and Madrid region under Grants TEC2012–37983-C03–02, P2013/MIT-2790.Publicad

Sensing Applications in Aircrafts Using Polymer Optical Fibres

We report on recent advances in the use of inexpensive polymer optical fibres (POFs) for sensing applications in avionics. The sensors analysed in this manuscript take advantage of the unique properties of polymers, such as high flexibility, elasticity, and sensitivity, and they range from strain, elongation, and vibration interrogators to level and temperature meters, leading to cost-effective techniques for structural health monitoring in aircraft structures. We also highlight recent power-supply methods using Power-over-POF in order to feed sensors remotely, and we discuss the constraints imposed by connectors on the performance of POF networks in aircrafts

Pós-processamento de fibras óticas para aplicações de sensores

In this work optical fiber post-processing techniques are proposed in order to produce optical fiber sensors (OFS) with lower costs, simplicity and with competitive characteristics compared with their counterparts. The first device was based on multimode interferometers. Those were fabricated by fusing multimode (MM) glass silica fibers (GOF) and MM polymer optical fibers (POF) between two single mode GOFs. For the GOF-based sensor, it was obtained a sensitivity of 4.6 pm/bar. Regarding the POF-based multimodal interferometer, a sensitivity of 58 pm/bar was reached, which corresponds to an enhancement of the sensitivity of twelve times when compared to the one obtained for GOF. Additionally, this sensitivity is five times higher than the one obtained for the POF Bragg grating technology. This improvement in sensitivity makes this sensor very promising since it can reach higher resolutions. The second fiber optic sensor discussed in this work consisted of mechanically induced long period gratings. These were obtained through very simple fabrication methodologies, which consisted of a periodical distribution of photopolymerizable resin onto a single mode GOF, followed by chemical corrosion, which allowed to periodically modulate the fiber diameter. This production method is more advantageous than its direct rivals since it applies cheap and easy to reproduce production techniques and does not require the use of photolithography or chemical vapor deposition technologies. The characterization of this structure to external parameters, such as: longitudinal strain, displacement and temperature revealed promising capabilities, since they allowed, not only the wavelength tuning of the spectral band, but also the optical power coupling strength. The results were very promising, as far as the displacement characterizations are concerned, since a measurement range of 0 - 60 mm was obtained, which is larger than those reported in the literature (i.e. up to 2 mm).Neste trabalho são propostas técnicas de pós-processamento de fibras óticas com o intuito de produzir sensores de fibra ótica de fácil fabrico, com baixo custo e com características competitivas comparadas com os demais sensores. O primeiro dispositivo baseou-se em interferómetros multimodais. Estes foram feitos através da fusão de fibras óticas multimodo tanto de vidro (GOF) como de polímero (POF) entre duas fibras óticas monomodo de vidro. Para o sensor à base de GOF foi obtida uma sensibilidade de 4.6 pm/bar. Já para o interferómetro multimodal baseado em POF, foi obtida uma sensibilidade de 58 pm/bar, que corresponde a uma melhoria da sensibilidade de doze vezes quando comparada com o sensor baseado em GOF. Além disso, esta é cinco vezes superior à obtida para tecnologia de redes de Bragg em POF. Esta melhoria na sensibilidade torna este sensor muito promissor, uma vez que permite obter resoluções muito maiores. O segundo sensor de fibra ótica abordado neste trabalho consistiu em redes de período longo mecanicamente induzidas. Estas foram obtidas através de metodologias de simples fabricação, que consistiam em distribuir periodicamente resina fotopolimerizável numa GOF-monomodo, seguido de um processo de corrosão química que permitiu modular periodicamente o diâmetro da fibra. Este método de produção é muito mais vantajoso comparado com os seus rivais diretos, uma vez que aplica técnicas de produção baratas e de simples reprodução, não exigindo a utilização de tecnologias de fotolitografia ou de deposição química de vapor. A caraterização desta estrutura a parâmetros externos, tais como: tensão longitudinal, deslocamento e temperatura revelaram capacidades promissoras, uma vez que permitiram não só a sintonização da banda espetral tanto em comprimento de onda como também em potência ótica de acoplamento. Os resultados foram bastante promissores no que concerne às caraterizações do deslocamento, uma vez que se obteve uma gama de medição de 0 - 60 mm, o que é maior que aquelas reportadas na literatura (i.e. até 2 mm).Mestrado em Engenharia Físic

Fiber optic sensors and self-reference techniques for temperature measurements in different industrial sectors

Mención Internacional en el título de doctorEl objetivo de este trabajo se centra especialmente en el desarrollo de sensores de fibra óptica y técnicas de autoreferencia para la medida de la temperatura en diferentes entornos industriales. El primer objetivo de este trabajo consiste en el diseño y desarrollo de un sensor de fibra óptica de bajo coste para la medida de la temperatura en transformadores de potencia y aplicaciones biomédicas. En estas aplicaciones, el uso de sensores de temperatura tradicionales resulta inadecuado debido a la presencia de fuertes interferencias electromagnéticas que pueden perturbar la lectura de la temperatura. Uno de los requisitos fundamentales para diseñar un sensor de temperatura que pueda usarse en aplicaciones biomédicas es el uso de materiales biocompatibles en su fabricación. En este sentido, una configuración simple que permite cumplir con los requisitos mencionados anteriormente es la modulación por intensidad en fibras poliméricas. Este tipo de sensores basan la lectura de la temperatura en medir las variaciones de potencia óptica en función de los cambios de temperatura que se aplican sobre el sensor. En este contexto, el uso de la tecnología asociada con la fibra óptica de plástico ofrece ventajas competitivas frente a otros materiales, como son: el uso de dispositivos opto-electrónicos de bajo coste, la posibilidad de utilizar conectores de baja precisión, la posibilidad de utilizar multiplexores y demultiplexores de muy bajo coste, entre muchas otras ventajas. A pesar de estas ventajas, los sensores de intensidad necesitan de esquemas de autoreferencia que eviten fluctuaciones de potencia que interfieran en la lectura de la temperatura. Estas fluctuaciones pueden provenir de fluctuaciones de potencia a lo largo del tramo de fibra óptica entre la unidad de control y el sensor, fluctuaciones de la fuente de luz por cambios en la corriente de alimentación, pérdidas de potencia por envejecimiento de la instalación, entre otras causas. El segundo objetivo de este trabajo consiste en promover el estudio y el desarrollo de técnicas de multiplexado y autoreferencia que implementen sensores fabricados en fibra óptica de plástico. Estas topologías deberán de utilizar dispositivos eficientes desde el punto de vista del consumo de potencia para mejorar con ello el balance de potencias del sistema y por tanto, poder utilizar este tipo de esquemas en redes de corto y medio alcance. Para alcanzar este objetivo, en este trabajo se desarrollan técnicas de autoreferencia y multiplexado de bajo coste basadas en multiplexación por longitud de onda vasta (CWDM, Coarse Wavelength Division Multiplexing). Esta técnica se caracteriza por su amplio desarrollo en el campo de telecomunicaciones como estándar para aplicaciones de corto o medio alcance en redes metropolitanas. Los multiplexores y demultiplexores diseñados para esta topología tienen una rejilla de longitudes de onda con una separación entre canales de 20nm. Este espaciado entre canales dificulta la multiplexación de un elevado número de dispositivos o sensores como podría llevarse a cabo si se usaran dispositivos basados en multiplexación por longitud de onda densa (DWDM, Dense Wavelength Division Multiplexing). Pero presentan una clara ventaja competitiva, los esquemas CWDM requieren bajas tolerancias en la fabricación de fuentes de luz, un control menos exhaustivo de la temperatura de la fuente, filtros ópticos de bajo coste y esquemas de diseño menos complejos. Los menores requisitos técnicos de los dispositivos utilizados con esta tecnología hacen que sea una topología interesante para su uso en redes de sensores de bajo coste. El tercer objetivo consiste en desarrollar sensores sin contacto basados en pirometría de dos colores para el sensado de la temperatura en procesos de mecanizado industrial...As a general aim, this work specifically focuses on the development of temperature sensors and self-reference techniques for temperature measurement in different industrial sectors. The first objective of this work is the design and development of a low-cost fiber optic sensor for measuring temperature in power transformers and biomedical applications where the presence of EMI prohibits the use of traditional sensors. Compatibility with the human being is a requirement when the temperature sensors are used in medical applications. Following simple fiber optic configurations, intensity sensors modulate the optical power loss as the temperature changes, thus providing the measurement as an optical intensity modulation signal. Polymer Optical Fiber (POF) technology, with very low-cost components, enables temperature sensing using a low precision connectors and lenses as well as simple multiplexing and demultiplexing devices, especially if compared with glass optical fibers. However, intensity sensors need a self-referencing method to minimize the influences of long-term aging of source and receptor characteristics, as well as undesirable random short-term fluctuations of optical power loss in the fiber link connecting the control unit, where the measurements are taken, to the remote sensing point, where the optical sensor is located. The second objective of this work is to promote, study and develop a multiplexing strategy to implement and scale POF sensor networks using low cost off-the-shelf devices, enhancing the power budget and keeping the self-reference of the measurements. This work focuses on low-cost Coarse WDM (CWDM) technology, where a grid of wavelengths with a 20nm channel spacing for target distance of up to tens of kilometres is specified. CWDM technology have lately been promoted in the field of telecommunication as standard for metro applications with shorter distances, lower network capacity and cost than Dense WDM (DWDM). This topology requires simpler, wider tolerance laser manufacturing, less laser accurate temperature control and reduced design complexity and cost of optical filters. These relaxed requirements make the CWDM technology an interesting approach for building low-cost self-referencing sensors networks. The development of this technology, adapted to the use of POF, can be carried out with the development of fiber Bragg gratings (FBG) in POF, providing an effective and compact strategy for exploiting fiber links for both propagating directions of the light with a single fiber lead. The third objective is to develop a non-contact two-colour fiber-optic pyrometer for temperature measures in the aerospace machining industry, enhancing the location measurement area, reducing the surface emissivity effect and keeping the self-reference of the measurement…The research work of this dissertation has been supported by the following Spanish projects: TEC2009-14718-C03-03 (DEDOS), and TEC2012-37983-C03-02 (CFOOT-TIC) of the Spanish Interministerial Commission of Science and Technology (CICYT); BES-2010-033348, EEBB-I-12-05434 and EEBB-1-13-07511 of the Spanish Ministry of Economy and Competitiveness; PRX12/00007 of Spanish Ministry of Education; P2013/MIT-2790, FACTOTEM-2/2010/00068/001 and S2013/MIT-2790 (SINFOTON-CM) of Autonomous Community of Madrid. Additional financial support was obtained from ICT COST Action TD1001: Novel and Reliable Optical Fiber Sensor Systems for Future Security and Safety Applications (OFSESA) of the European Union.Programa Oficial de Doctorado en Ingeniería Eléctrica, Electrónica y AutomáticaPresidente: Tianxin Yang.- Secretario: Ricardo Vergaz Benito.- Vocal: Kevin Heggart