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Fiber Bragg Grating Sensors : An Exploration Of Applications In Diverse FieldsGuru Prasad, A S 12 1900 (has links) (PDF)
Sensors have become essential elements in human life for safe and comfortable existence in the ever demanding world. Various technologies over decades have contributed in their own way fulfilling innumerable sensing requirements. The discovery of optical sensor technologies has revolutionized the sensing field due to their inherent advantages. Among the large number of fiber optic sensor technologies, FBG based sensors have become widely known and popular within and outside the photonics community and has seen a prominent rise in their utilization.
This thesis explores the use of FBG sensors for a wide range of applications scanning across a variety of engineering and medical applications, in the areas of civil engineering, biomechanical engineering, aerospace engineering, geoengineering, etc. It also deals with newer methods of packaging FBG sensors for the measurement of specific engineering parameters like strain, temperature, pressure, displacement and vibration.
In the field of civil engineering, FBG sensors are employed for strain sensing on a prism and furthermore tested on a full size brick wallet. During this study, emphasis is made on substituting traditional sensors by specially packaged FBG sensors with the intent of either enhancing the sensing system’s performance or in merging/uniting the inherent advantages of FBG sensors.
In the area of biomechanics, a novel sensor methodology using FBG sensors, for measuring surface strains generated on the skin of the calf muscle during various leg exercises is proposed. This methodology is used to address one of the most critical and life threatening issues in long distance air travel, namely the Deep Vein Thrombosis. Further, a FBG sensor based plantar sensing plate, is designed and developed, to measure plantar strain distribution in foot and also to analyze the postural stability.
In the field of aerospace engineering, FBG sensors are used for addressing two of the most vital issues; Structural Health Monitoring (SHM) and direct measurement of pressure and temperature on the surface of an aircraft under hypersonic wind flow. Carbon Fiber Composite coupon level testing is carried out to obtain a generic strain calibration factor for the FBG sensor. Further, FBG sensors are exploited for the direct measurement of absolute temperature and pressure on the leeward surface of blunt cone at hypersonic wind speeds.
In the domain of geoengineering, the feasibility studies have been undertaken to use a FBG as a seismic sensor and as a bore-well characterizing sensor. A novel FBG seismic sensor package is developed using a single FBG sensor to pick up the seismic waves propagating through the ground generated from earthquakes and ground tremors. Further, FBG sensors are used for measurement of temperature profiles in a bore-well to delineate and characterize the behavior of fractures during seasonal climatic changes. To summarize, the present thesis demonstrates a comprehensive experimental study which bring out the utility of FBG sensors in a variety of challenging applications.
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Durability of Embedded Fibre Optic Sensors in CompositesLevin, Klas January 2001 (has links)
This thesis concerns various aspects of the durability offibre optic sensors embedded in composite. Since repair orreplacement of embedded sensors is not generally possible, thefunctional reliability of embedded sensors is one of the mostimportant prerequisites for successful use. The main researchobjective was to investigate the interaction between the sensorand the composite, and how this is affecting the mechanical andoptical sensor response. Fibre optic sensors embedded incomposite structures induce local stress concentrations whenthe composite is subjected to mechanical loads andenvironmental changes such as temperature and moisture. Acomplex transfer of stresses through the interfaces between theembedded sensor and the composite occurs and can result inlarge local stresses in the composite and a significant changein the response of the embedded sensor. These stressconcentrations make the interfaces susceptible todebonding. The sensor performance was studied experimentally andnumerically. Some basic results were generated for the EFPI andBragg grating sensors. The phase-strain response was determinedduring static and fatigue loading. The results showed that thesensors were more reliable in compression than in tensilestatic and fatigue loading. Generally, the sensor reliabilityduring loading was significantly improved for the Bragg gratingsensors over that of the EFPI sensor, as an effect of thesensor geometry. This was also demonstrated in theinvestigations on impacts. Impacts do not necessarily result indamage in the composite, but might cause debonding or otherfailure modes in the sensor area. Large, local stressconcentrations occur at several positions in the EFPI sensor,which pointed out that this sensor type was not suitable forembedded applications. The shift in focus from the sensor concept based on the EFPIsensor to that based on the Bragg grating sensor manifesteditself in several studies. The calculated deformation fieldaround an embedded optical fibre was verified in experimentsusing a high-resolution moiré interferometric technique.Furthermore, the improvement in the coating technology wasverified. A significant higher interfacial strength wasobtained with the silane-treated glass surface. The resultsindicated that at least a twofold improvement of the shearstrength was obtained. To simultaneously measure the in-plane strain components andthe temperature change, embedded Bragg grating sensors werearranged in a rosette configuration. The relationship betweenthe optical response from each sensor and the strains in thelaminate was numerically and analytically established. Damage lead to stress redistribution in the sensor region,which may influence the output from the embedded Bragg gratingsensor. The effect was numerically evaluated for interfacialdamage, and was compared to that of a sensor with undamagedinterface. The results showed that debonding might have asignificant influence, in particular for combined thermal andmechanical loading. <b>Keywords</b>: composites, fibre optic sensor, embedded, EFPIsensor, Bragg grating sensor, durability, fatigue, impact,strain measurement, interface, stress analysis
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Durability of Embedded Fibre Optic Sensors in CompositesLevin, Klas January 2001 (has links)
<p>This thesis concerns various aspects of the durability offibre optic sensors embedded in composite. Since repair orreplacement of embedded sensors is not generally possible, thefunctional reliability of embedded sensors is one of the mostimportant prerequisites for successful use. The main researchobjective was to investigate the interaction between the sensorand the composite, and how this is affecting the mechanical andoptical sensor response. Fibre optic sensors embedded incomposite structures induce local stress concentrations whenthe composite is subjected to mechanical loads andenvironmental changes such as temperature and moisture. Acomplex transfer of stresses through the interfaces between theembedded sensor and the composite occurs and can result inlarge local stresses in the composite and a significant changein the response of the embedded sensor. These stressconcentrations make the interfaces susceptible todebonding.</p><p>The sensor performance was studied experimentally andnumerically. Some basic results were generated for the EFPI andBragg grating sensors. The phase-strain response was determinedduring static and fatigue loading. The results showed that thesensors were more reliable in compression than in tensilestatic and fatigue loading. Generally, the sensor reliabilityduring loading was significantly improved for the Bragg gratingsensors over that of the EFPI sensor, as an effect of thesensor geometry. This was also demonstrated in theinvestigations on impacts. Impacts do not necessarily result indamage in the composite, but might cause debonding or otherfailure modes in the sensor area. Large, local stressconcentrations occur at several positions in the EFPI sensor,which pointed out that this sensor type was not suitable forembedded applications.</p><p>The shift in focus from the sensor concept based on the EFPIsensor to that based on the Bragg grating sensor manifesteditself in several studies. The calculated deformation fieldaround an embedded optical fibre was verified in experimentsusing a high-resolution moiré interferometric technique.Furthermore, the improvement in the coating technology wasverified. A significant higher interfacial strength wasobtained with the silane-treated glass surface. The resultsindicated that at least a twofold improvement of the shearstrength was obtained.</p><p>To simultaneously measure the in-plane strain components andthe temperature change, embedded Bragg grating sensors werearranged in a rosette configuration. The relationship betweenthe optical response from each sensor and the strains in thelaminate was numerically and analytically established.</p><p>Damage lead to stress redistribution in the sensor region,which may influence the output from the embedded Bragg gratingsensor. The effect was numerically evaluated for interfacialdamage, and was compared to that of a sensor with undamagedinterface. The results showed that debonding might have asignificant influence, in particular for combined thermal andmechanical loading.</p><p><b>Keywords</b>: composites, fibre optic sensor, embedded, EFPIsensor, Bragg grating sensor, durability, fatigue, impact,strain measurement, interface, stress analysis</p>
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Real-Time Signal Processing and Hardware Development for a Wavelength Modulated Optical Fiber Sensor SystemMusa, Shah M. 09 September 1997 (has links)
The use of optical fiber sensors is increasing widely in civil, industrial, and military applications mainly due to their, (a) miniature size, (b) high sensitivity, (c) immunity from electro-magnetic interference, (d) resistance to harsh environments, (e) remote signal processing ability, and, (f) multiplexing capabilities. Because of these advantages a variety of optical fiber sensing techniques have evolved over the years having potentials for myriad of applications. One very challenging job, for any of these optical fiber sensing techniques, is to implement a stand alone system with the design and development of all the signal processing models along with the necessary hardware, firmware, and software satisfying the real-time signal processing requirements. In this work we first develop the equations for the system model of the wavelength modulated extrinsic Fabry-Perot interferometric (EFPI) optical fiber sensor, and then design and build all the hardware and software necessary to implement a stand-a / Ph. D.
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[en] EFFECTS AND APPLICATIONS OF NON-HOMOGENEOUS STRAINS IN BRAGG GRATINGS / [pt] EFEITOS E APLICAÇÕES DE DEFORMAÇÕES NÃO HOMOGÊNEAS EM REDES DE BRAGGADRIANO FERNANDES PINHO 21 September 2005 (has links)
[pt] Redes de Bragg em fibras ópticas (RBF) são formadas por
modulações periódicas
introduzidas no índice de refração do núcleo de fibras
ópticas. Estes componentes
comportam-se como filtros espectrais de banda passante, ou
seja, quando iluminados por
um sinal óptico de banda larga, refletem apenas uma fina
fatia espectral de luz, cujo
centro, o comprimento de onda de Bragg, é proporcional ao
período espacial da
modulação no índice de refração. As RBF têm encontrado
aplicações importantes no
sensoriamento das mais diversas grandezas, sendo hoje
utilizadas em sistemas de
monitoramento para vários segmentos industriais, tais como
os setores de petróleo e gás,
construção civil e aeroespacial, que, estima-se, respondem
em conjunto por cerca de 70%
destas aplicações. Em diversas situações o sensoriamento
com RBF baseia-se em
medidas indiretas da grandeza de interesse, sendo
empregados mecanismos de
transdução que transformam variações do mensurando em
deformações na fibra óptica.
Nestes casos, um problema que deve ser tratado com atenção
é o acoplamento entre
temperatura e deformação, uma vez que as RBF são sensíveis
a estas duas variáveis. Não
raro, a alternativa é utilizar simultaneamente duas RBF
para obter-se a compensação de
temperatura na medida de deformação.
Este trabalho apresenta um estudo sobre deformações não
homogêneas em redes de
Bragg e discute aplicações de duas técnicas que podem ser
utilizadas como alternativas
para eliminar o efeito da temperatura no sensoriamento de
deformação com apenas uma
RBF. A primeira delas explora a birrefringência óptica
induzida na RBF por
carregamentos transversais à fibra óptica. A segunda
baseia-se nos efeitos sobre o
espectro refletido pela rede de Bragg quando submetida a
um campo de deformações
longitudinais não uniformes ao longo da direção axial da
fibra óptica. No trabalho são
apresentados protótipos e dispositivos que exploram tais
técnicas para a medida simultânea de pressão e
temperatura. Esses protótipos foram projetados com auxílio
de
ferramentas CAD e modelados utilizando-se o método de
elementos finitos em conjunto
com a teoria de modos acoplados da Rede de Bragg. As
previsões obtidas utilizando-se
estes modelos mostraram-se bastante próximas dos
resultados das implementações
experimentais dos protótipos, indicando que a metodologia
de modelagem desenvolvida
pode ser aplicada nos projetos de transdutores baseados
nas duas técnicas estudadas. / [en] Fiber Bragg gratings (FBG) are modulations in the
effective refractive index of
optical fibers, introduced in a small length along the
fiber core. Such components operate
as narrow band reflective filters, that is, when
illuminated by a broad-band light source,
they reflect a narrow spectral band centered at a specific
wavelength, the Bragg
wavelength. This wavelength is proportional to the spatial
period of the refractive index
modulation. Fiber Bragg gratings have find an increasing
number of applications as
sensors for different quantities, and today are being
employed as part of permanent, real
time monitoring systems in various industrial segments.
The oil and gas sector, together
with civil infrastructure and aeronautics and aerospace,
account for almost 70% of this
applications. In a number of situations, FBG sensing is
based on indirect measurements
of the quantity being monitored, and a transduction
mechanism is employed to transform
changes in the measured quantity in strain sensed by the
optical fiber. Since the FBG is
sensitive to strain and temperature, proper temperature
compensation is always
necessary. Usually, a second grating is employed to
simultaneously measure temperature
and strain, performing the required compensation.
This thesis presents a study on effects due to non-
homogeneous strains in the
Bragg grating and discusses application of two different
techniques, based on these
effects, to allow temperature compensated strain
measurement using a single FBG. The
first technique explores strain induced optical
birefringence when the fiber is loaded
transversely. The second technique is based on changes in
the spectral shape of the light
signal reflected by the grating when subjected to non
homogeneous axial strain fields.
Prototypes of pressure and temperature transducers based
on these techniques have been
developed. These prototypes have been designed by
employing CAD techniques and
modeled using the finite element method in conjunction
with the theory of coupled
modes for fiber Bragg gratings. Comparisons between
results provided by theoretical models and experimental
realizations of the prototypes are very close,
demonstrating that
the developed approach can be applied to design
transducers based on the discussed
techniques. Results obtained with the proposed pressure
and temperature sensors are also
encouraging indicating that the two techniques are
suitable for industrial applications.
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[en] APPLICATIONS OF FIBER BRAGG GRATING SENSORS IN THE MEASUREMENT OF PH AND OF STRAIN IN HARD THIN FILMS / [pt] APLICAÇÕES DE SENSORES A REDE DE BRAGG EM FIBRAS ÓPTICAS NA MEDIÇÃO DE PH E DEFORMAÇÃO DE FILMES FINOS DE ALTA DUREZASULLY MILENA MEJIA QUINTERO 07 November 2006 (has links)
[pt] Este trabalho versa sobre duas diferentes aplicações de
sensores a redes de
Bragg em fibra óptica. A primeira consiste no
desenvolvimento de uma técnica
de sensoriamento do pH empregando fibra óptica, que visa a
monitoração
contínua e permanente deste parâmetro em poços de petróleo
depletados e de
injeção. Nesta aplicação, as redes de Bragg são acopladas,
através de um
mecanismo transdutor, a sistemas poliméricos que respondem
a alterações do pH
apresentando uma variação expressiva de seu volume. O
tempo de resposta e o
fator de inchamento do sistema polimérico foram
caracterizados para valores de
pH 3, 4, 5, e 6, em soluções aquosas contendo sais
dissolvidos em concentrações
típicas das encontradas em águas de formação. As medições
foram realizadas a
temperaturas e pressões ambientes, assim como na presença
de óleo, e após a
pressurização do sistema polimérico até 5000 psi.
Diferentes mecanismos
transdutores foram projetados e construídos, e suas
respostas, avaliadas em
soluções aquosas com composição similar à das águas de
formação. Foram
estimadas a sensibilidade da técnica e as principais
fontes de incerteza na
medição do pH. Procurou-se também avaliar a funcionalidade
dos mecanismos
transdutores visando uma futura instalação em poço. Na
segunda aplicação, é
proposta uma técnica para a medição in situ da tensão
residual induzida em
filmes finos de alta dureza durante sua deposição em
câmaras de sputtering
assitido por rádio-frequência e campo magnético. A técnica
é constituída por
uma viga em aço engastada, tendo uma de suas faces
instrumentada com um
conjunto de redes de Bragg a fibra óptica, enquanto a face
oposta é exposta ao
fluxo de íons do material a ser depositado. O sistema
sensor é instalado em uma
câmara que opera sob alto vácuo, enquanto os aparelhos de
leitura permanecem
no exterior. A resposta do protótipo em função de
variações do campo
magnético e da temperatura no interior da câmara foi
levantada. Em seguinda,
foram realizadas medições da deformação da viga durante a
deposição de filmes
de sílica, de óxido de titânio-índio, e de carbeto de
silício. A tensão residual dos filmes foi calculada e
comparada com resultados de medições de curvatura do
substrato realizadas empregando um perfilômetro. Tensões
residuais de 6 MPa
até 0,2 Gpa foram obtidas durante as diferentes deposições. / [en] This work treats of two different applications of optical
fiber Bragg grating
sensors. The first application consists of a pH sensing
technique that employs
optical fiber to permanent and continuously monitor the pH
in depleted and
injection oil wells. In this application, the Bragg
gratings are coupled by a
transduction mechanism to a polymeric system which
responds to pH variations
with a large volume change. The response time as well as
the swelling factor of
the polymeric system at pH 3, 4, 5, and 6 have been
characterized in aqueous
solutions with dissolved salts in concentrations typical
of those found in
formation waters. Experiments have been carried out at
room temperature and
pressures, in the presence of oil, and after
pressurization up to 5000 psi. Several
mechanisms of transduction have been designed,
constructed, and tested in
solutions similar to the formation waters. The sensitivity
of the technique and the
main sources of uncertainties related to the pH
measurement have been
investigated. Also, the functionality of the mechanisms
has been evaluated
aiming at a future installation in the petroleum wells.
The second application
investigated is a technique for in situ measurement of the
residual stress induced
in hard thin films during deposition by RF magnetron
sputtering. The sensing
technique consists of a cantilever steel beam. One of the
surfaces of the beam is
instrumented using optical fiber Bragg gratings; the
opposite face is exposed to
the ion flux that originates the thin film. The sensing
system is installed in a
vacuum chamber while the interrogating apparatus remains
outside. The
prototype has been characterized with respect to
variations of the magnetic field
and the temperature inside the chamber. Measurements of
the beam strain have
been carried out during deposition of silica, indium-
titanium oxide, and silicon
carbide thin films. The residual stresses have been
calculated and the results
compared with data obtained using perfilometry. Residual
stress values varying
from 6 MPa up to 200 MPa have been obtained during the
different deposition processes.
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[pt] ACELERÔMETRO TRIAXIAL A REDES DE BRAGG / [en] TRIAXIAL BRAGG GRATING ACCELEROMETER03 September 2004 (has links)
[pt] Desde o final da década de 80 a indústria de fibras
óticas têm passado por avanços consideráveis. Através de
técnicas controladas, as fibras ópticas podem gerar sinais
associados a uma vasta gama de grandezas físicas
funcionando como sensores denominados de Sensores a Fibra
Óptica (SFO s). Diversas técnicas podem ser empregadas
para tal, e entre as existentes a baseada em redes de
Bragg é a que mais tem se destacado. O interesse por
transdutores empregando esta técnica se justifica
pelas vantagens proporcionadas pelo uso da luz, tais como
sua capacidade de multiplexação, boa relação sinal/ruído,
medições a longas distâncias, imunidade a campos
eletromagnéticos, ausência de faísca, entre outras.
Neste trabalho buscou-se desenvolver um transdutor e uma
técnica de medição baseada em sensores a rede de Bragg
para medição de vibrações mecânicas. Um acelerômetro
óptico triaxial é projetado e construído. Diferentes
modelos foram testados em busca das características de
desempenho desejadas. Simulações numéricas empregando o
método dos elementos finitos auxiliaram na decisão por
melhores desenhos para o transdutor. Resultados de testes
experimentais e calibrações empregando um sistema de
aquisição de sinais desenvolvido são mostrados. Medições
de longa duração para avaliação de estabilidade do sistema
e efeitos de temperatura também são apresentados. / [en] Since the end of the 1980s, the fiber optics industry has
experienced considerable advances. Through a number of
controlled techniques, fiber optics can generate signals
associated with a vast array of physical measures, working
as sensors denominated Optical Fiber Sensors (OFS s).
Many different techniques can be employed to achieve this
objective. Among these, the one based on Bragg networks
has received the greatest amount of attention. The
interest in transducers employing this technique is
justified by the advantages of using light, such as its
multiplexing capability, good signal-to-noise ratio,
possibility of long distance measurements, immunity
to electromagnetic fields, and absence of sparks. In the
present work, a transducer and measurement technique based
on Bragg network sensors vibration are developed, in order
to measure mechanical vibrations. A triaxial optical
accelerometer is designed and built. Different models are
tested in the search for the desired performance
characteristics. Numerical simulations employing the
finite element method help the decision making process for
better transducer designs. Results from experimental and
calibration tests using a newly developed signal
acquisition system are presented. Long duration
measurements to evaluate system stability and temperature
effects are also shown.
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All-Fiber Sensing Techniques For Structural Health Monitoring And Other ApplicationsMadhav, Kalaga Venu 09 1900 (has links)
In this thesis, we explore the four aspects of fiber Bragg grating sensors: mathematical modeling of Fiber Bragg Grating response/spectral characteristics, fabrication using phase mask, application and interrogation. Applications of fiber Bragg gratings, also known as in-fiber gratings, with emphasis on their sensing capabilities, interrogation of an array of sensors and their performance in structural health monitoring scenario are documented.
First, we study the process of photosensitivity phenomenon in glasses, in particular GeO2:SiO2 glasses. For mathematical modeling we consider the 1-D refractive index profile along the propagation axis of an optical fiber drawn from the preform of such glasses. These 1-D index structures exhibit a bandgap for propagation along the fiber axis. We show how the bandgap is dependent on the two structural parameters: index periodicity and effective refractive index. The mathematical model provides the characteristics of three sensor parameters -resonance wavelength also known as the Bragg wavelength (λB ), filter bandwidth (ΔλB ), and reflectivity (R). We show that the evolution of the index structure in germanosilicate glasses is dependent on the inscription parameters such as exposure time, intensity of the laser used for inscribing, the interference pattern, and coherence of the laser system. In particular, a phase mask is used as the diffffacting element to generate the required interference pattern, that is exposed on the photosensitive fiber. We present a mathematical model of the electromagnetic diffraction pattern behind the phase mask and study the effect of the limited coherence of the writing laser on the interference pattern produced by the diffracting beams from the mask.
Next, we demostrate the sensing capabilities of the fiber Bragg gratings for measuring strain, temperature and magnetic fields. We report linearity of 99.7% and sensitivity of 10.35pm/◦C for the grating temperature sensor. An array of gratings assigned with non-overlapping spectral windows is inscribed in a single fiber and applied for distributed sensing of structural health monitoring of an aircraft’s composite air-brake panel. The performance of these sensors is compared with the industry standard resistance foil gauges. We report good agreement between the two gauges (FBG and RSG).
In some applications it is more desirable to know the spectral content, rather than the magnitude of perturbation. Fiber Bragg gratings sensors can be used to track events that occur in a very small span of time and contain high frequencies. Such applications demand very high speed wavelength demodulation methods. We present two interrogation techniques: wavelength-shift time-stamping (WSTS) and reflectivity division multiplexing (RDM). WSTS interrogation method employs the multiple threshold-crossing technique to quantize the sensor grating fluctuations and in the process produces the time stamps at every level-cross. The time-stamps are assembled and with the a priori knowledge of the threshold levels, the strain signal is reconstructed. The RDM methodology is an extension of the WSTS model to address multiple sensors. We show that by assigning unique reflectivities to each of the sensors in an array, the time-stamps from each of the sensors can be tagged. The time-stamps are collected by virtue of their corresponding pulse heights, and assembled to reconstruct the strain signal of each of the array sensor. We demonstrate that the two interrogation techniques are self-referencing systems, i.e., the speed at which the signals are reconstructed is instantaneous or as fast as the signal itself.
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Development of Fiber Bragg Grating Sensor Based Devices for Force, Flow and Temperature Measurement for Emerging Applications in Biomedical DomainShikha, * January 2016 (has links) (PDF)
Efficient and accurate sensing of various parameters is needed for numerous applications. In this regard, different categories of sensors play a significant role and different applications require diverse sensing mechanisms owing to the operating conditions and field constraints. Among the several sensor methodologies available, optical fiber sensors have found significant attention, because of their advantages such as negligible foot print, small mass, immunity to Electromagnetic Interference, etc.
In the category of optical fiber sensors, Fiber Bragg Grating (FBG) sensors have found importance in many fields such as health monitoring of civil structures, environmental monitoring involving gas & humidity sensing, monitoring parameters like pressure, tilt, displacement, etc. In the recent times, FBGs have found applications in biomedical, biomechanical and biosensing fields.
A FBG is a periodic change of the refractive index of the core of a single mode optical fiber along its longitudinal axis. The periodic modulation in the index of refraction is obtained by exposing a photosensitive germanium-doped silica fiber to an intense UV laser beam. FBGs, in the basic form, can sense strain and temperature. However, in recent years, several newer sensing applications of FBGs have been demonstrated. Some of the main features of the FBG sensor which qualify them for diverse sensing applications are high sensitivity, large operational bandwidth, multiplexing & multi modal sensing capability, etc.
In this thesis work, FBG sensor based devices have been developed for newer applications in bio-medical fields for the measurement of force, flow and temperature.
Particularly, novel transduction methodologies have been proposed, in order to convert the measurand parameter into a secondary parameter that can be sensed by the FBG sensor.
The evaluation of the force required for a spinal needle to penetrate various tissue layers from skin to the epidural space is vital. In this work, a novel technique for dynamic monitoring of force experienced by a spinal needle during lumbar puncture using Fiber Bragg Grating (FBG) sensor has been developed. The Fiber Bragg Grating Force Device (FBGFD) developed, measures the force on the spinal needle due to varied resistance offered by different tissue layers during its traversal.
The effect of gauge of the spinal needle used for the lumbar puncture procedure affects the force required for its insertion into the tissue. The FBGFD developed, has been further utilized for a comparative study of the force required for lumbar puncture of various tissue layers with spinal needle of different gauges. The results obtained may serve as a guideline for selection of suitable gauge spinal needle during lumbar puncture minimizing post puncture side effects on patients.
The pulmonary function test carried out using a spirometer, provides vital information about the functional status of the respiratory system of the subject. A Fiber Bragg Grating Spirometer (FBGS) has been developed which has the ability to convert the rate of air flow into a shift in wavelength that can be acquired by the FBG sensor. The FBGS can dynamically acquire the complete breathing sequence comprising of the inhalation phase, pause phase and exhalation phase in terms of the air flow rate along with the time duration of each phase. Methods are adopted to analyse and determine important pulmonary parameters using FBGS and compare these parameters with those obtained with a commercially available hospital grade pneumotachograph spirometer.
Thermal imaging is one of the emerging non-invasive neuro-imaging techniques which can potentially indicate the boundaries of a brain tumor. The variation in tissue surface temperature is indicative of a tumor existence. In this work a FBG temperature sensor (FBGTS) has been developed for thermography of a simulated tissue using Agar material. The temperature of the embedded heater which mimics a brain tumor along with the surface temperature of the tissue model, is acquired using FBGTSs simultaneously. Further, the surface temperatures are studied for varying heater temperatures as well as varying positions of the heater in the simulated tissue model.
To conclude, FBG based devices have been developed in this work, for applications in biomedical domain, with appropriate transduction methodologies for sensing different parameters such as force, flow and temperature.
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Design, Development and Validation of Fiber Bragg Grating Sensor Based Devices for Detecting Certain Healthcare ParametersChethana, K January 2016 (has links) (PDF)
Several sensor technologies have been developed and experimented over the last few decades to cater various needs of medical diagnostics. Among these, fiber optic sensors, in particular, Fiber Bragg Grating (FBG) based sensors have attracted considerable attention due to their inherent advantages such electrical passiveness, immunity to Electro Magnetic Interference (EMI), chemical inertness, etc. The present research work focuses on design, development and validation of FBG sensor based devices for measurement of certain healthcare parameters in the context of foot function/gait cycle, cardiac and breathing activity, nostril dominance, hand grip/wrist angle force function, etc. The experimental work presented here emphasizes on the effectiveness and competitiveness of the FBG devices developed, in comparison with standard tools such as Accelerometer, Load cell, Electronic Stethoscope, Electromyogram and Dynamometer.
In the field of human balance, stability and geriatrics, two independent FBG devices namely, Fiber Bragg Grating based Stability Assessment Device (FBGSAD) and Optical Sensor Ground Reaction Force measurement Platform (OSGRFP) have been designed, developed and experimented for postural stability assessment and gait analysis respectively. The result of these studies have significant implications in understanding of the mechanism of plantar strain distribution, identifying issues in gait cycles, detecting foot function discrepancies, identifying individuals who are susceptible to falls and to qualify subjects for balance and stability.
In the field of ergonomic assessment, Fiber Braggs Grating based Hand Grip Device (FBGHGD) is designed and developed for the measurement of hand grip force which helps in the understanding of several important biomechanical aspects such as neuromuscular system function, overall upper-limb strength, vertebral fracture, skeletal muscle function, prediction of disability, incapacity, mortality and bone mass density (forearm, skeletal sites, spine, hip etc.). Further as an extension of this work, the FBGHGD is used for measurement of force generated by the wrist in different positions of the flexion and extension which relates to the wrist muscle activity and its enactment.
In the field of cardiac activity monitoring, a novel, in-vivo, non-invasive and portable device named Fiber Bragg Grating based Heart Beat Device (FBGHBD) is developed for the simultaneous measurement of respiratory and cardiac activities. The work involves designing FBGHBD, validating its performance against traditional diagnostic systems like electronic stethoscope, exploration of its clinical relevance and the usage of FBGHBD in studies involving normal persons and patients with myocardial infarction. The unique design of FBGHBD provides critical information such as nascent morphology of cardiac and breathing activity, heart rate variability, heart beat rhythm, etc., which can assist in early clinical diagnosis of many conditions associated to heart and lung malfunctioning. Further, the scope of this work extends towards evaluating several signal processing algorithms and demonstrating a suitable signal processing architecture for real-time extraction of heart beat and respiratory rates along with its nascent morphologies for critical health care application.
In the area of breath monitoring, a Nostril Pressure and Temperature Device (NPTD) is designed and developed which aims at simultaneous, accurate and real-time measurement of nostril air flow pressure and temperature to aid in clinical diagnosis of nasal dysfunction and associated nose disorders. The results of NPTD can offer certain vital features like breathing pattern, respiratory rate, changes in individual nostril temperature/pressure, nostrils dominance, body core temperature etc., which can assist in early clinical diagnosis of breathing problems associated with heart, brain and lung malfunctioning. Since the research work in this thesis involve experiments engaging human subjects, necessary approvals from the ethical committee is obtained before the experiments and required ethical procedures are followed during all the experimental trials.
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