Multi-axial strain monitoring of fibre reinforced thermosetting plastics using embedded highly birefringent optical fibre Bragg sensors

There is a growing interest in the use of fibre reinforced plastics (FRPs) as high-grade construction material for variouw applications that need to be lightweight, yet strong in sometimes harsh loading conditions. Despite the growing popularity of structural composite materials, one has to realize that their mechanical behaviour is significantly different compared to conventional isotropic construction materials. Strain monitoring of an in-service structure should greatly enhance the insight and confidence in the (long-term) behaviour of high performance composite structures. Structural health monitoring necessitates the possibility of measuring multi-axials strain fields. High birefringent optical fibres (HiBi-fibres) with Bragg grating can become a solution in this matter. Designing a multi-axial strain sensor based on optical FBGs should meet several basic requirements which are discussed in this dissertation

Two-axis bend measurement with Bragg gratings in multicore optical fiber

We describe what is to our knowledge the first use of fiber Bragg gratings written into three separate cores of a multicore fiber for two-axis curvature measurement. The gratings act as independent, but isothermal, fiber strain gauges for which local curvature determines the difference in strain between cores, permitting temperature-independent bend measurement. (C) 2003 Optical Society of America

Development of a fiber-based shape sensor for navigating flexible medical tools

Robot-assisted minimally invasive surgical procedure (RAMIS) is a subfield of minimally invasive surgeries with enhanced manual dexterity, manipulability, and intraoperative image guidance. In typical robotic surgeries, it is common to use rigid instruments with functional articulating tips. However, in some operations where no adequate and direct access to target anatomies is available, continuum robots can be more practical, as they provide curvilinear and flexible access. However, their inherent deformable design makes it difficult to accurately estimate their 3D shape during the operation in real-time. Despite extensive model-based research that relies on kinematics and mechanics, accurate shape sensing of continuum robots remains challenging. The state-of-the-art tracking technologies, including optical trackers, EM tracking systems, and intraoperative imaging modalities, are also unsuitable for this task, as they all have shortcomings. Optical fiber shape sensing solutions offer various advantages compared to other tracking modalities and can provide high-resolution shape measurements in real-time. However, commercially available fiber shape sensors are expensive and have limited accuracy. In this thesis, we propose two cost-effective fiber shape sensing solutions based on multiple single-mode fibers with FBG (fiber Bragg grating) arrays and eccentric FBGs. First, we present the fabrication and calibration process of two shape sensing prototypes based on multiple single-mode fibers with semi-rigid and super-elastic substrates. Then, we investigate the sensing mechanism of edge-FBGs, which are eccentric Bragg gratings inscribed off-axis in the fiber's core. Finally, we present a deep learning algorithm to model edge-FBG sensors that can directly predict the sensor's shape from its signal and does not require any calibration or shape reconstruction steps. In general, depending on the target application, each of the presented fiber shape sensing solutions can be used as a suitable tracking device. The developed fiber sensor with the semi-rigid substrate has a working channel in the middle and can accurately measure small deflections with an average tip error of 2.7 mm. The super-elastic sensor is suitable for measuring medium to large deflections, where a centimeter range tip error is still acceptable. The tip error in such super-elastic sensors is higher compared to semi-rigid sensors (9.9-16.2 mm in medium and large deflections, respectively), as there is a trade-off between accuracy and flexibility in substrate-based fiber sensors. Edge-FBG sensor, as the best performing sensing mechanism among the investigated fiber shape sensors, can achieve a tip accuracy of around 2 mm in complex shapes, where the fiber is heavily deflected. The developed edge-FBG shape sensing solution can compete with the state-of-the-art distributed fiber shape sensors that cost 30 times more

Fibras ópticas especiais para sensoriamento

Orientador: Cristiano Monteiro de Barros CordeiroTese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb WataghinResumo: Nesta tese, fibras ópticas especiais são estudadas para fins de sensoriamento. Primei-ramente, propomos a estrutura denominada fibra capilar com núcleo embutido (embedded-core capillary fibers) para realização de sensoriamento de pressão. Estudos numéricos e analíticos foram realizados e mostraram que altas sensibilidades a variações de pressão poderiam ser al-cançadas com esta estrutura simplificada, que consiste de um capilar dotado de um núcleo, dopado com germânio, em sua parede. Experimentos permitiram medir uma sensibilidade de (1.04 ± 0.01) nm/bar, que é um valor alto quando comparado a outros sensores de pressão ba-seados em fibras microestruturadas. Ademais, estudamos fibras do tipo surface-core, que são fibras cujos núcleos são colocados na superfície externa da fibra. Nesta abordagem, redes de Bragg foram utilizadas para obter sensores de índice de refração ¿ fazendo-se uso da interação entre o campo evanescente do modo guiado no núcleo e o ambiente externo à fibra ¿ e de cur-vatura ¿ ao se explorar o fato de que, nestas fibras, o núcleo se encontra fora do centro geomé-trico da mesma. As sensibilidades a variações de índice de refração e curvatura medidas, 40 nm/RIU em torno de 1.41 e 202 pm/m-1 comparam-se bem a outros sensores baseados em redes de Bragg. Outrossim, fibras capilares poliméricas foram investigadas como sensores de temperatura e pressão. Para a descrição do sensor de temperatura, usou-se um modelo analítico para simular o espectro de transmissão dos capilares e a sua dependência com as variações de temperatura. No que tange à aplicação de sensoriamento de pressão, variações nas espessuras dos capilares devido à ação da pressão foram calculadas e relacionadas à sensibilidade da me-dida de monitoramento. Nestas duas aplicações, realizações experimentais também são repor-tadas. Finalmente, oportunidades adicionais de sensoriamento ao se utilizar fibras ópticas es-peciais são apresentadas, a saber, um sensor de pressão para dois ambientes baseados em fibras de cristal fotônico, um sensor de três parâmetros baseado em redes de Bragg, fibras afinadas e interferência multimodal, um sensor de nível de líquido baseado em redes de Bragg e interfe-rência multimodal e um sensor de temperatura baseado em fibras embedded-core preenchidas com índio. Os resultados aqui reportados demonstram o potencial das fibras ópticas em forne-cerem plataformas de sensoriamento para alcançar medidas de diferentes tipos de parâmetros com alta sensibilidade e resolução adequadaAbstract: In this thesis, specialty optical fibers for sensing applications are investigating. Firstly, we propose the embedded-core capillary fiber structure for acting as a pressure sensor. Analyt-ical and numerical studies were performed and showed that high pressure sensitivity could be achieved with this simplified fiber structure, which consists of a capillary structure with a germanium-doped core placed within the capillary wall. Experiments allowed measuring a sensitivity of (1.04 ± 0.01) nm/bar, which is high when compared to other microstructured optical fiber-based pressure sensors. Moreover, we studied the so-called surface-core optical fibers, which are fibers whose cores are placed at the external boundary of the fiber. In this approach, Bragg gratings were used to obtain refractive index ¿ making use of the interaction between the guided mode evanescent field and the external medium ¿ and directional curva-ture sensors ¿ by exploring the off-center core position. The measured refractive index and the curvature sensitivities, respectively 40 nm/RIU around 1.41 and 202 pm/m-1, compares well to other fiber Bragg grating-based sensors. Additionally, antiresonant polymer capillary fibers were investigated as temperature and pressure sensors. For the temperature sensing descrip-tion, one used an analytical model to simulate the transmission spectra of such fibers and the dependence on temperature variations. Regarding the pressure sensing application, pressure-induced capillary wall thickness variations were analytically accounted and related to the sys-tem pressure sensitivity. In both these applications, experimental data were presented. Finally, additional opportunities using specialty optical fibers were presented, namely, a photonic-crystal fiber-based dual-environment pressure sensor, a three parameters sensor using Bragg gratings, tapered fibers and multimode interference, a liquid-level sensor based on Bragg grat-ings and multimode interference, and a temperature sensor based in an embedded-core fiber filled with indium. The results reported herein demonstrates the potential of optical fibers for providing sensing platforms to attain measurements of different sort of parameters with highly sensitivity and improved resolutionsDoutoradoFísicaDoutor em Ciências152993/2013-4CNP

Review of Fiber Optic Displacement Sensors

Displacement Measurements Are of Significant Importance in a Variety of Critical Scientific and Engineering Fields, Such as Gravitational Wave Detection, Geophysical Research, and Manufacturing Industries. Due to the Inherent Advantages Such as Compactness, High Sensitivity, and Immunity to Electromagnetic Interference, in Recent Years, Fiber Optic Sensors Have Been Widely Used in an Expansive Range of Sensing Applications, Ranging from Infrastructural Health Monitoring to Chemical and Biological Sensing. of Particular Interest Here, Fiber Optic Displacement Sensors Have Gained Wide Interest and Have Evolved from Basic Intensity Modulation-Based Configurations to More Advanced Structures, Such as Fiber Bragg Grating (FBG)-Based and Interferometric Configurations. This Article Reviews Specifically the Advanced Fiber Optic Displacement Sensing Techniques that Have Been Developed in the Past Two Decades. Details Regarding the Working Principle, Sensor Design, and Performance Measures of FBG-Based, Interferometers-Based (Including the Fabry-Perot Interferometer, the Michelson Interferometer, and the Multimode Interferometer), Microwave Photonics-Based, and Surface Plasmon Resonance-Based Fiber Optic Displacement Sensors Are Given. Challenges and Perspectives on Future Research in the Development of Practical and High-Temperature Tolerant Displacement Sensors Are Also Discussed

Opto-Mechanical Interactions in Multi-Core Optical Fibers and Their Applications

[EN] Optical fibers containing multiple cores are being developed towards capacity enhancement in space-division multiplexed optical communication networks. In many cases, the fibers are designed for negligible direct coupling of optical power among the cores. The cores remain, however, embedded in a single, mechanically-unified cladding. Elastic (or acoustic) modes supported by the fiber cladding geometry are in overlap with multiple cores. Acoustic waves may be stimulated by light in any core through electrostriction. Once excited, the acoustic waves may induce photo-elastic perturbations to optical waves in other cores as well. Such opto-mechanical coupling gives rise to inter-core cross-phase modulation effects, even when direct optical crosstalk is very weak. The cross-phase modulation spectrum reaches hundreds of megahertz frequencies. It may consist of discrete and narrow peaks, or may become quasi-continuous, depending on the geometric layout. The magnitude of the effect at the resonance frequencies is comparable with that of intra-core cross-phase modulation due to Kerr nonlinearity. Two potential applications are demonstrated: single-frequency opto-electronic oscillators that do not require radio-frequency electrical filters, and point-sensing of liquids outside the cladding of multi-core fibers, where light cannot reach.This work was supported in part by a Starter Grant from the European Research Council (ERC) under Grant H2020-ERC-2015-STG 679228 (L-SID), in part by the Israeli Ministry of Science and Technology under Grant 61047, and in part by the Spanish Ministry of Economy and Competitiveness under the DIMENSION TEC2017 88029-R Project. H. H. Diamandi was supported by the Azrieli Foundation for the award of an Azrieli Fellowship. The work of J. Madrigal was supported by Universitat Politecnica de Valencia scholarship PAID-01-18. The work of D. Barrera was supported by Spanish MICINN fellowship IJCI-2017-32476.Diamandi, HH.; London, Y.; Bergman, A.; Bashan, G.; Madrigal-Madrigal, J.; Barrera, D.; Sales Maicas, S.... (2020). Opto-Mechanical Interactions in Multi-Core Optical Fibers and Their Applications. IEEE Journal of Selected Topics in Quantum Electronics. 26(4):1-13. https://doi.org/10.1109/JSTQE.2019.2958933S11326

High temperature tolerant optical fiber inline microsensors by laser fabrication

Fiber sensors are particularly attractive for harsh environment defined by high temperature, high pressure, corrosive/erosive, and strong electromagnetic interference, where conventional electronic sensors do not have a chance to survive. However, the key issue has been the robustness of the sensor probe (not the fiber itself) mostly due to the problems stemmed from the traditional assembly based approaches used to construct fiber optic sensors. For example, at high temperatures (e.g., above 500°C), the thermal expansion coefficient mismatch between different composited parts has a high chance to lead to sensors\u27 malfunction by breaking the sensor as a result of the excessive thermo-stress building up inside the multi-component sensor structure. To survive the high temperature harsh environment, it is thus highly desired that the sensor probes are made assembly-free. We are proposing to fabricate assembly-free fiber sensor probes by manufacturing various microstructures directly on optical fibers. This dissertation aims to design, develop and demonstrate robust, miniaturized fiber sensor probes for harsh environment applications through assembly-free, laser fabrication. Working towards this objective, the dissertation explored three types of fiber inline microsensors fabricated by two types of laser systems. Using a CO₂ laser, long period fiber grating (LPFG) and core-cladding mode interferometer sensors were fabricated. Using a femto-second laser, an extrinsic Fabry-Perot interferometric (EFPI) sensor with an open cavity was fabricated. The scope of the dissertation work consists of device design, device modeling/simulation, laser fabrication system setups, signal processing method development and sensor performance evaluation and demonstration. This research work provides theoretical and experimental evidences that laser fabrication technique is a valid tool to fabricate previously undoable miniaturized photonic sensor structures, which can avoid complicated assembly processes and, as a result, enhance robustness, functionality and survivability of the sensor for applications in harsh environments. In addition, a number of novel optical fiber sensor platforms are proposed, studied and demonstrated for sensing and monitoring of various physical and chemical parameters in high temperature harsh environments --Abstract, page iii

Sensing using Specialty Optical Fibers

Fiber optic based sensing is a growing field with many applications in civil and aerospace engineering, oil and gas industries, and particularly in harsh environments where electronics are not able to function. Optical fibers can be easily integrated into structures, are immune to electromagnetic interference, can be interrogated from remote distances, and can be multiplexed for distributed measurements. Because of these properties, specialty fiber designs and devices are being explored for sensing temperature, strain, pressure, curvature, refractive index, and more. Here we show a detailed analysis of a multicore fiber (MCF) for sensing, including its design and optimization in simulation, as well as experimental operation when used as sensor. The multicore fiber sensor\u27s performance as a function of temperature, strain, bending, and acoustic waves are all explored. The MCF sensors are shown to be able to withstand temperatures up to 1000°C, making them suitable to be harsh environment sensors. Additionally, a simple method for increasing the sensitivity of the MCF to longitudinal force is shown to multiple the sensitivity of the MCF sensor by a factor of seven. Also, a configuration for decoupling force and temperature will be presented. Finally, a developing all-fiber device, a photonic lantern, will be shown in conjunction with the MCF in order to increase sensitivity, add directional sensitivity, and lower the cost of the sensor interrogation for bending measurements. In addition to the multicore fiber, an analysis of anti-resonant hollow core fiber (ARHCF) is also presented. The fibers\u27 design-dependent propagation losses are explored, as well as their higher order mode content. Also, a potential application of an ARHCF for an in-fiber Raman air sensor is introduced, and the design optimization in simulation is shown

In-situ deformation monitoring of aerospace qualified composites with embedded improved draw tower fibre Bragg gratings

Aerospace certified fibre reinforced plastics (FRPs) are extreme performing construction materials, which today are increasingly applied in primary structures of the new generation aircrafts (e.g. Boeing 787, Airbus 350, Bombardier C-Series), such as the fuselage, the wings and the fin. An interesting aspect on the technological point of view of sensing is that airplane manufacturers such as Airbus and Boeing are looking at incorporating health-monitoring systems (such as optical fibre sensors, especially fibre Bragg gratings) that will allow the airplane to self-monitor and report maintenance requirements to ground-based computer systems. However, one has to realize that the mechanical behaviour of anisotropic FRPs is significantly different compared to conventional isotropic construction materials. In this dissertation, the author focuses on monitoring the strain and (permanent) deformation in carbon reinforced plastic laminates with embedded fibre Bragg gratings. The research is divided in two main parts. In the first part of this research, the existing fibre draw tower technology is utilized, to manufacture an improved version of the existing in-line high quality, draw tower fibre Bragg gratings (DTG®s). With respect to accurate measurements and structural integrity, the research focuses on reducing the total diameter of the optical fibre, so the incorporation in the reinforcement fibres is enhanced and the distortion in the composite is reduced. The author elaborates in detail the methods of strain and temperature calibrations and the different setups which are applied. Additionally, with respect to the high temperatures during the composite manufacturing process, the thermal stability of the DTG®s is studied at elevated temperatures (>300°C). In the second part, the author embeds the DTG®s in specific types of thermoset and thermoplastic carbon reinforced plastic laminates. The author applies the embedded DTG®s in several stages of the composite lifetime. Starting with the monitoring of the composite manufacturing process and ending with fatigue testing until failure of the composite laminates. During the different experiments, the sensors are subjected to high temperatures, high pressures, extreme longitudinal strains and transverse strains and in the mean time, they are employed to very accurately measure (multi-axial) strains inside composites at microstrain level (~10 6)

Optical sensors for cultural heritage and biomedical applications

The current Ph.D. thesis is articulated in 4 different research paths. The main research topic is on the fiber Bragg grating (FBG) sensor and its applications, mainly related to the conservation of the original status of the artworks. The second topic is related to the development of a new methodology for measuring the cracking of the Structural Health Monitoring (SHM) of cultural heritage. In the third topic, it is addressed the subject on the complex diatribe related to the risk in delivering anesthesia; field in which I have been also working, being a Biomedical Engineer. Finally, in the last topic it is proposed a biomechanics study on the patellar taping with the purpose of finding a correlation between the taping and a neuromuscular response. A new era of pollution requires an important focus on the conservation of archaeological sites and monuments. In the last years, great efforts were made to develop various sensors for different tasks; the FBG was one of the most studied thanks to the multitude of applications and the surprising performances. An original fiber optic sensor that combines the fiber Bragg gratings with a pH responsive polymer coating for monitoring the pH of the rains on critical and prestigious monuments is proposed. In this study, the arrangement setup of the optical sensor is modeled with Comsol Multiphysics (Wave Optics Module), based on the FEM (Finite Element Method) solver. Monitoring the pH of the rain can be used by experts to predict and control the corrosion of specific materials, especially limestone and marble, thus scheduling timely restoration. This also depends on the materials under analysis and it can have an important impact in terms of cost reductions and higher maintenance efficiency. In conclusion, the swelling response of hydrogels to the change of surrounding pH allowed the development of a model of hydrogel coated FBG pH sensor. Modelling the FBG pH sensor for monitoring the rain in archaeology and in cultural heritage provided innovative results in terms of high sensitivity and small dimensions of the device, allowing better intervention planning. In the first chapter, a preliminary study regarding the optical ring resonator is conducted because, ultimately, the goal is to realize a sensor that combines the FBG and the ring resonator for future developments in order to improve the sensor performances. Along with the development of the FBG sensor, a new methodology for measuring the cracking for the Structural Health Monitoring (SHM) of cultural heritage is also studied. The methodology is characterized by being minimally invasive on the artefact that has to be preserved, which is one of the main qualities required in this field. The approach is to determine the relative distance between two optical tags, using advanced fitting algorithms for the objective function. Different kinds of objective-function were taken into account in order to identify the best configuration to determine the fitting parameters, useful to the SHM. The optical tags are introduced for this scope; they are nothing but adhesive labels with appropriate images, through which, by using advanced fitting methods and algorithms, it is possible to determine the absolute and relative position and three-dimensional rotations of the images. The third chapter of this thesis deals with the risk and perception of risk in delivering anesthesia. The study examines the different perceptions of risk associated with anesthesia systems from the viewpoints of the product manufacturer and the caregiver. Only little research has been done on the impact of the perception of risk for patient safety in anesthesia. The role of the manufacturer in mitigating the perception of risk is central in the work. The risk was examined as the probability of negative occurrences based on the Medical Device Reportable (MDR) events and these risks were compared to how the caregiver perceives and manages them when delivering anesthesia. Analysis of the manufacturer’s public Medical Device Reportable (MDR) events data was performed in the US market and it represents the actual risk achieved; the bibliographic review provided a perspective on how the risk is perceived and managed by the caregiver when delivering anesthesia. The goal of the research path is to highlight how the role of the manufacturers can have an impact on the reduction of perception of risk in anesthesia, increasing patient safety. Finally, a biomechanical proposal on the estimation of Centre of Mass (CoM) trajectory has been developed. Motion capture systems and force platforms are still considered the gold standard for the estimation of accurate CoM measurements. In the last decade, several methods based on inertial sensors systems have been proposed based on double integration of acceleration signals of pelvis-worn sensors (M. J. Floor-Westerdijk, 2012). Although the portability of those methodologies is higher, drift errors due to extremely lengthy time acquisitions affect measurements, limiting their use. For the purpose of avoiding drift error and providing an accurate tool for ambulatory and/or home CoM assessment, the accuracy of a novel method based on a Biomechanical Model (BM) will be investigated. Among the large number of potential applications, this novel approach could be used in the identification of the effects of the patellar taping on neuromuscular control. More specifically, the patellar taping technique proposed by McConnell (J. McCONNELL, 1986) allows patients to engage in pain-free physical therapy exercises, by medializing the patella. Although this technique has been demonstrated to reduce the perceived pain of patients with patellofemoral pain syndrome and improve neuromuscular activity (N. Aminaka and P. A. Gribble, 2008), a deeper investigation on how patellar tape influences postural stability thought CoM assessment could be of great interest in the long term management of Chondromalacia Patellae. It has been demonstrated, in fact, that patellar taping affects knee proprioception other than relieving pain in subjects with patellofemoral pain syndrome (M. J. Callaghan, 2008). The aim of this research program is to pursue through static and dynamic tasks performed twice both by healthy subjects and not-healthy ones, with and without patellar tape