Lab-on-fiber technology: a new avenue for optical nanosensors

The "lab-on-fiber" concept envisions novel and highly functionalized technological platforms completely integrated in a single optical fiber that would allow the development of advanced devices, components and sub-systems to be incorporated in modern optical systems for communication and sensing applications. The realization of integrated optical fiber devices requires that several structures and materials at nano- and micro-scale are constructed, embedded and connected all together to provide the necessary physical connections and light-matter interactions. This paper reviews the strategies, the main achievements and related devices in the lab-on-fiber roadmap discussing perspectives and challenges that lie ahead

Real time measuring system of multiple chemical parameters using microstructured optical fibers based sensors

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

SnO2-MOF-Fabry-Perot optical sensor for relative humidity measurements

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

Optical fiber sensors based on nanostructured materials for environmental applications

La contaminación ambiental es la presencia de agentes físicos, químicos o biológicos presentes en el agua, suelo y aire; siendo perjudiciales para la salud de las personas, así como para la vida vegetal y animal. Las actividades económicas son esenciales para el desarrollo de la sociedad, sin embargo, muchas de estas actividades son una fuente de contaminación constante. Por ejemplo, la fuga de fluidos y gases en plantas industriales afectan negativamente a la salud e higiene para la elaboración de alimentos, bebidas, aditivos y materias primas causando un impacto ambiental y económico negativo en la industria. La búsqueda continua de métodos para el desarrollo de sistemas de medición es una característica de la evolución tecnológica de la humanidad. Las fibras ópticas presentan varias ventajas para ser empleadas en sistemas sensores; tales ventajas son: inmunidad a la interferencia electromagnética, dimensiones reducidas, ligeras, bajas pérdidas, fácil multiplexación y resistencias a la corrosión, entre otras. En general, podemos encontrar una amplia gama de aplicaciones en la industria para el desarrollo de sensores en fibra óptica. Sin embargo, en esta tesis se han seleccionado tres aplicaciones industriales de interés relevante: detección de gas amoniaco a bajas concentraciones, detección de adulteración en bebidas alcohólicas y detección de adulteración de combustibles. Se caracterizan los parámetros de los sensores desarrollados tales como la sensitividad, reversibilidad, reproducibilidad y precisión para la medición de cada tipo de sensor. Los resultados obtenidos en esta tesis serán útiles en el estudio de nuevos materiales aplicables a sensores ópticos, permitiendo la apertura a nuevas vías de investigación en el campo de los sensores en fibra óptica para aplicaciones industriales.Environmental pollution is the presence of physical, chemical or biological agents in water, soil and air which are harmful to our health, safety and welfare of the people as well as plant and animal life. Economic activities are essential to the development of society; however, many of these activities are a constant source of contamination. For example, leakage of fluids and gases in industrial plants adversely affect the health and hygiene for food processing, beverages, additives and raw materials causing serious environmental and economic impact on the general industry. The continual search for methods for developing measurement systems is a feature in the technological evolution of humankind. Optical fibers exhibit several advantages such as being immune to electromagnetic interferences, reduced dimensions, lightweight, low losses, easy multiplexation and resistant to corrosion for the development of optical fibers sensors. However, we selected three applications were the principle of operation of our sensor provides an advantage over other reported sensors: gaseous ammonia detection for low concentrations, adulteration of alcoholic beverages detection and combustibles quality control. The overall objective of this research is to design, fabricate, deploy and verify the correct operation of optical fiber structures for the identification of interesting liquid and gaseous environmental pollutants. The sensors parameters such as its sensitivity, reversibility, reproducibility and accuracy of measurement for each type of sensor are also characterized. These results obtained from this thesis would be a useful work in the study of new materials applicable to optical sensors, while opening new avenues of research in the field of optical fiber sensors for industrial applications.La realización de esta tesis ha sido posible gracias al apoyo recibido por parte del Consejo Nacional de Ciencia y Tecnología (CONACYT) bajo el contrato CB-2010/157866 y CB-2010/156529, así como de la Comisión Interministerial de Ciencia y Tecnología a través de la financiación de los proyectos CICYT fondos FEDER TEC2010-17805.Programa Oficial de Doctorado en Tecnologías de las Comunicaciones (RD 1393/2007)Komunikazioen Teknologietako Doktoretza Programa Ofiziala (ED 1393/2007

Understanding the Radiation Effects on Fiber Optic Sensors

In this dissertation, the effects of radiation (gamma, neutron or mixed gamma and neutron) on optical fiber sensors are studied and new techniques for real-time measurement of radiation-induced macroscopic changes in optical fibers are presented. It is crucial among the research and development efforts in the nuclear energy field to conduct experiments in Advanced Test Reactor (ATR) to support lifetime extension, novel fuels and materials development, better fuel management, and enhanced safety of existing as well as future nuclear power plants (NPP). Due to their unparalleled and unique advantages over traditional sensors, optical fiber sensors are deemed potential candidates for their use in nuclear environments. However, optical fibers are susceptible to high levels of ionizing radiation emitted by fission reactors which are characterized by the highest levels of gamma dose, high flux of neutrons and potentially high temperatures depending on location in a reactor core. It is essential to accurately determine the information related to physical parameters such as temperature, pressure, and strain in nuclear environments for the safety of the existing and future NPPs. This dissertation starts with inverting a transmission mode long period grating (LPG) to reflection mode using a novel and cost-effective metal coating method since transmission mode LPG limits it applications in tight spaces or in nuclear fields. To understand the metal coating and metal coverage effects on the reflection spectrum of LPG, modeling work was performed, and it was validated by experimental work. We have shown that the sensitivity of LPGs to physical parameters in both transmission and reflection modes are almost the same. Next, we have modeled the radiation effects on different fiber optic sensors, proposed empirical models, and performed numerical analysis to understand the effects of nuclear environments on fiber optic sensors. We analyzed the real-time data from fiber Bragg gratings (FBGs) exposed to high neutron fluence and high temperature environments within the ATR at Idaho National Laboratory (INL). We have found that incoming radiation significantly drifts the characteristic signal of FBGs, leading to a temperature measurement error when FBGs are dedicated to temperature sensing. It is well known that neutron and gamma irradiation compacts silica optical fibers, resulting in a macroscopic change in the refractive index (RI) and geometric structure. The change in RI and linear compaction in a radiation environment is caused by three well-known mechanisms: (1) radiation induced attenuation (RIA), (2) radiation induced compaction (RIC), and (3) radiation induced emission (RIE). While RIA degrades the signal strength by creating different types of color centers in the silica fiber, RIC alters the density, and hence RI by displacing the host material atoms. However, Kramers-Kronig relation states that absorption, and hence the RIA, also modifies the RI of the silica fiber. Apart from RIA and RIC, other phenomena such as temperature, dose rate, stress relaxation, and dopant compositions exchange may change the RI. To overcome these problems, we have proposed an effective technique to measure the change in RI and compaction of optical fiber due to any specific phenomena the fiber is subjected to, including RIC, RIA, dopant diffusion, temperatures, dose, dose rate, etc. By knowing the individual contribution of RI and fiber length to the signal drift, it is possible to reduce the radiation induced signal drift in optical fiber sensors and provide accurate information regarding the temperature inside a radiation environment. Fission gas detection in nuclear environments is another important aspect that needs to be focused on. Pressure induced by fission gases during irradiation may lead to loss of coolant accident (LOCA), which can cause severe damage to the NPPs. We have modeled and fabricated optical fiber-based sensors to enable real-time monitoring of fission gases, which allows understanding the implications of fission gas release during an accident, important for safe and high performance