This dissertation presents the fabrication and analysis of in-fiber devices based on elliptical core D-shaped optical fiber. Devices created inside optical fibers are attractive for a variety of reasons including low loss, high efficiency, self-alignment, light weight, multiplexibility, and resistance to electromagnetic interference. This work details how D-fiber can be used as a platform for a variety of devices and describes the creation and performance of two of these devices: an in-fiber polymer waveguide and a surface relief fiber Bragg grating. In D-fiber the core is very close to the flat side of the ‘D’ shape. This proximity allows access to the fields in the fiber core by removal of the cladding above the core. The D-fiber we use also has an elliptical core, allowing for the creation of polarimetric devices. This work describes two different etch processes using hydrofluoric acid (HF) to remove the fiber cladding and core. For the creation of devices in the fiber core, the core is partially removed and replaced with another material possessing the required optical properties. For devices which interact with the evanescent field, cladding removal is terminated before acid breaches the core. Etching fibers prepares them for use in the creation of in-fiber devices. Materials are placed into the groove left when the core of a fiber is partially removed to form a hybrid waveguide in which light is guided by both the leftover core and the inserted material. These in-fiber polymer waveguides have insertion loss less than 2 dB and can potentially be the basis for a number of electro-optic devices or sensors. A polarimetric temperature sensor demonstrates the feasibility of the core replacement method. This work also describes the creation of a surface relief fiber Bragg gratings (SR-FBGs) in the cladding above the core of the fiber. Because it is etched into the surface topography of the fiber, a SR-FBG can operate at much higher temperatures than a standard FBG, up to at least 1100 degrees Celsius. The performance of a SR-FBG is demonstrated in temperature sensing at high temperatures, and as a strain sensor.

This dissertation presents the novel creation of a surface relief fiber Bragg grating on the flat surface of a D-shaped optical fiber. In order to produce an efficient surface relief grating the grating must be etched into the surface of the glass fiber close to the core. A short etch that removes the cladding above the core is performed in order to decrease the core-to-flat distance and allow the light to interact with the grating on the flat surface. Due to the unique D-shape of the optical fiber the mechanical integrity of the fiber remains high even after the fabrication process. For traditional fiber Bragg gratings the index modulation occurs in the core of the optical fiber. While this method can produce highly reflective gratings they are not well suited for many sensing applications. For example, the operating temperature range is limited to a few hundred degrees Celsius before the index modulation returns to a more uniform index profile. Also because the gratings are created in the core of the fiber, interaction with the surrounding environment is limited. The surface relief fiber Bragg grating created for this work overcomes some of the sensing challenges of traditional gratings. The major accomplishments of this dissertation show a dramatic increase in operating temperature to over 1000 degrees Celsius, the ability to measure multi-dimensional bend, the ability to measure material changes around the fiber such as chemical concentration, and the ability to use a Vernier effect to dramatically increase the sensors sensitivity. In addition to the sensing applications of this work a more thorough understanding of the reflection and transmission properties of the surface relief grating is also presented. Implementation of the transfer matrix method for simulation of the gratings is also shown to be a fast and accurate modeling tool for predicting the grating response.

Afin de répondre à une demande toujours croissante en capteurs, des systèmes de mesures optiques permettant la détection de récepteurs naturels ou synthétiques sur des substrats inorganiques ont été élaborés. Par résonance des plasmons de surface (RPS), nous avons montré que des films minces à base de copolymères de N-(acryloxysuccinimide) et de dérivés acrylates de poly (éthylène glycol) ou qu'un film mince de polyglycidol présentaient une résistance accrue à l'adsorption non-spécifique des protéines et qu'ils permettaient un greffage covalent de biomolécules par l'intermédiaire de leurs groupements réactifs respectifs. Un nouveau capteur basé sur la technologie des réseaux de Bragg en angle gravés sur une fibre optique a ensuite été développé et caractérisé grâce à l'emploi de films multicouches présentant des propriétés sélectives et réversibles de reconnaissance par formation de complexes d'inclusion entre des polymères de cyclodextrine et des dérivés de l'adamantane. A partir de cette fibre optique, il a aussi été possible de suivre en temps réel les transition de conformation interfaciale de chaînes de poly (acide acrylique) immobilisée de façon covalente au support en fonction du pH. Pour les deux approches, multicouche et covalente, des biocapteurs pour la détection de l'albumine de sérum bovin (BSA) ont été réalisés. De plus, les propriétés d'inclusion des cyclodextrines ont aussi été mises à profit pour complexer des petites molécules hydrophobes telles que le toluène pour élaborer un capteur chimique. Enfin, afin d'éviter l'utilisation d'un matériel biologique, des polymères à empreinte moléculaire (MIP) ont aussi été développés. La sélectivité, la spécificité et la sensibilité des films minces envers la molécule cible d'acide gallique, ont été évaluées par voltammétrie cyclique. Les résultats obtenus permettent d'affirmer que ces polymères se comportent comme de véritables récepteurs artificiels / To answer to an always increasing request in sensors, optical measurement systems allowing the detection of natural or synthetic receptors on inorganic substrates were elaborated. By Plasmon Surface Resonance (SPR), we showed that thin films constituted with copolymers of N-(acryloxysuccinimide) and poly (ethylene glycol) acrylates derivatives or that a thin film of polyglycidol presented a strong resistance in non-specific protein adsorption and that they allowed a covalent grafting of biomolecules through their respective reagent groupings. A new sensor, a tilted fiber Bragg gratings was then developed and characterized by using multilayers films presenting selective and reversible properties of recognition by forming inclusion complexes between polymers of cyclodextrine and adamantine derivatives. From this optical fiber, it was also possible to follow in real time interfacial conformation transition, according to the pH, of poly(acrylic acid) chains immobilized covalently on the substrate. For both approaches, biosensors for the detection of bovin serum albumin (BSA) were realized. Furthermore, the inclusion properties of cyclodextrine compounds allowed also the complexation of small hydrophobic molecules such as toluene, which forming chemical sensors. Finally, to avoid the use of a biological material, molecular imprinted polymers (MIP) were also developed. Their selectivity, specificity and sensibility toward gallic acid, the target molecule, were estimated by cyclic voltammetry. The results confirm that these polymers can be considered as artificial receptors

This thesis work deals with the development of three different categories of interrogation techniques for Fiber Bragg Grating based sensor networks. Such networks are used for structural health monitoring and other applications. A bulk grating based interrogation system is described first, which includes an optical source, switch, circulator, embedded controller, and software. The center wavelength determination technique employed is detailed and is shown to be highly accurate from test data. The comparison with resistance strain gauges is presented which shows that the system developed provides an accurate strain reconstruction. The system is also compared with a commercial optical spectrum analyzer and is found to exhibit good accuracy and fidelity. The system has been field tested on an aircraft structure with 14 sensors spread over 4 channels. Strain data reconstruction from these tests is shown to accurately reproduce the loading conditions. A second system developed is based on the matched filter technique using a mechanical fiber stretcher; the details of this system are presented with a mathematical treatment of the technique. The design of the fiber stretcher is also described. This design is regarded to be novel since it tries to provide large interrogation bandwidths using a parallel topology. The results of tests have shown good resolution and comparative tests with resistance strain gauges have shown accurate reproduction of strain. Finally, an interrogation system based on a wavelength tunable source is presented. This system is a precursor to a time division multiplexed interrogation system, which has also been described. Three laser configurations have been set up and characterized. The laser sweep tests have been performed on two configurations and a sensor grating reconstruction test has also been carried out.

The different topics covered in this thesis include photosensitivity in germanosilicate fibers/glasses and application of fiber Bragg grating sensors in simultaneous strain and temperature discrimination. Fiber Bragg Gratings are wavelength dispersive refractive index structures manufactured through ultra-violet (UV) exposure of optical fibers. Their applications range from wavelength division multiplexing filters, dispersion compensators and fiber laser resonators for telecommunication applications to different types of point or distributive sensors for a variety of applications. One aim of this thesis has been to understand the mechanism of photosensitivity in germanosilicate fibers/preforms. Studies undertaken in this part of the thesis include thermal dynamics of Fiber Bragg Gratings and nano-indentation on ultra-violet irradiated germanosilicate glass preforms. An interesting, periodic appearance of a new peak has been observed in the reflected spectrum of Bragg grating inscribed in a germanosilicate fiber during thermal treatment. The new peak occurs on the longer wavelength side of the spectrum during heating and on the shorter wavelength side during cooling, following an identical reverse dynamics. A commercial grating with 99.9% reflectivity also shows a similar decay dynamics. The observed temperature induced distortion in refractive index modulation profile has been understood in the light of compaction-densification model. It is proposed that during the fabrication process of a grating, the modulation in the thermal expansion coefficient brought about by the interference fringes results in a non-uniform expansion throughout the grating length which in turn results in the distortion of the refractive index profile with increase/decrease in temperature. Since the reflection spectrum of a grating can be approximated as the Fourier transform of the refractive index profile, any distortion in the index profile results in the observed anomalous behaviour in the reflection spectrum. Nano-indentation studies have been performed to measure the changes in mechanical properties of a glass preform subjected to different levels of ultra-violet exposure. The results reveal that short term exposure leads to an appreciable increase in the Young’s modulus suggesting the densification of the glass, confirming the compaction-densification model. However, on prolonged exposure, the Young’s modulus decreases, which provides the first direct evidence of dilation in the glass leading into the Type IIA regime. The present results rule out the hypothesis that continued exposure leads to an irreversible compaction and prove that index modulation regimes are intrinsic to the glass matrix. In the second part of the thesis, three different schemes have been proposed for the use of Fiber Bragg Gratings as strain-temperature discriminating sensors: (a) The first method is based on the measurement of the different characteristic wavelength shifts of two types of gratings. Strain and temperature sensitivities of a Type I Bragg grating (G1) in germania doped silica fiber, fabricated under normal conditions, and zero strain, are compared with that of a Bragg grating inscribed under pre-strained condition (G2). Experimental results show that both, strain and temperature sensitivities of G1 and that of G2 are different. Based on this study, we have proposed an approach which enables simultaneous discrimination of axial strain and temperature. (b) In the second method, a single sensing element has been used to encode strain and temperature into an additional parameter other than the wavelength shift. The thermal out-diffusion of germanium from the core of a photosensitive fiber under elevated temperature is exploited to form a Fabry-Perot filter with a single Fiber Bragg Grating. The filter is fabricated using the standard phase-mask technique and one-time exposure. Energy Dispersive X-Ray analysis is used to measure the out-diffusion. The filter is used as a sensor for simultaneous measurement and discrimination of strain and temperature. The proposed technique, where a single grating is used to discriminate the parameters, provides a large advantage over other existing methods. (c) In the third method, a compact design based on cross-wire arrangement of Fiber Bragg Gratings having identical Bragg resonance and different reflectivity is proposed for simultaneously sensing strain (uniaxial) and temperature. Two gratings are assembled orthogonal to each other on an aluminium base. The cross-wire design allows the two sensors to experience the same temperature but different strain. The gratings are identified by their respective reflectivity and, strain and temperature are resolved from the shift in Bragg wavelength. The proposed design exploits the fact that strain is a vector and temperature is a scalar parameter. This sensor has wide industrial application in discriminating strain from temperature effects.

The research that is presented in this thesis can be divided into two major parts. The first part concerns longitudinally pumped, bulk Er-Yb lasers. In these lasers, the main limitation is the thermal shortcomings of the phosphate glass host material. From the laser experiments and the spectroscopic measurements on crystalline host materials, as well as an investigation to bring further light to the physical background of the involved dynamics, the thesis presents some novel results that contribute to the search for a crystalline replacement. The second part concerns novel laser concepts applied to Yb-doped double tungstate lasers. Different crystal orientations are investigated, such as an athermal orientation for reduced thermal lensing and a conical refraction orientation for complete polarization tuning. Furthermore, the introduction of volume Bragg gratings in the cavity enables wide spectral tuning ranges and extremely low quantum defects. Regarding the first part, the main results are the achievement of 15 % slope efficiency in a monolithic, continuous-wave Yb:GdCOB laser and the achievement of Q-switching of the same laser. The Q-switched pulse durations were around 5-6 ns and the Q-switched slope efficiency was 11.6 %. For both lasers, a maximum output power of 90 mW was obtained, which is close to ordinary glass lasers under similar conditions. A spectroscopic investigation into the Er,Yb-codoped double tungstates was also performed and the results have enabled mathematical modeling of the fluorescence dynamics in these materials. Finally, the temperature dependence of the dynamics in Er,Yb:YAG was studied and the results have given some insight into the physical background of the mechanisms involved. Regarding the second part, different end-pumped Yb:KReW laser cavities were constructed to demonstrate the different concepts. With a laser crystal cut for propagation along the athermal direction at 17º angle clockwise from the dielectric direction Nm, the thermal lens could be reduced by 50 %. In these experiments the maximum output power was 4 W at 60 % slope efficiency. In another cavity incorporating a volume Bragg grating in a retroreflector set-up, the wavelength could be continuously tuned between 997 - 1050 nm. The spectral bandwidth was 10 GHz and the peak output power was 3 W. The same output power could also be obtained at 1063 nm with the grating positioned as an output coupler instead. If, on the other hand, the grating was positioned as an input coupler, 3.6 W output power at 998 nm was obtained at a quantum defect of only 1.6 %. Furthermore, using a crystal oriented for propagation along an optic axis, internal conical refraction could be used to establish arbitrary control of the polarization direction as well as the extinction ratio. Even unpolarized light could be enforced despite the highly anisotropic medium. With this configuration, the maximum output power was 8.6 W at 60 % slope efficiency which equals the performance of a reference crystal with standard orientation. The completely novel concepts of laser tuning with Bragg grating retroreflectors, of low quantum defect through Bragg grating input couplers and of polarization tuning by internal conical refraction can all easily be applied to several other laser materials as well. / QC 20100713

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.

The objective of this thesis is to study of optical effects, arising in the form of non-uniform waveguide structure, complicated refractive index profiles or due to pulse propagation in dense wavelength division multiplexing (DWDM) optical communication systems. These effects are important and critically influence the performance of DWDM optical systems. A comprehensive survey of current literature on optical effects due to nonuniform optical structure and nonlinear optical effects is first done, showing their advantages and disadvantage in optical communication systems. A survey on methods of optical waveguide analysis is also done. The main contribution has been made to three main aspects of the problem : Accurate analysis of uniform/non-uniform optical waveguides with arbitary refractive index profiles Pulse propagation and distortion in DWDM Raman amplification systems. Use of non-uniform FBG to compensate for pulse distortion We study several existing analytical techniques developed so far for analyzing the mode of non-uniform optical waveguide structures. Later, we verify the analytical results by finite element method (FEM). The convergence study is also carried out. A new computational technique is proposed modifying the finite element method to analyze complex refractive index profiles required for the analysis, namely single mode step index profile, multi clad fiber, W -profile, chirp profile etc. An accuracy of 10−4 in the calculation of propagation constant/eigen-value is demonstrated. Dispersion characteristics of optical fibers w.r.t. different profile parameters is evaluated. A modification to scalar BPM is proposed and applied to study the effects of inhomogeneities along the propagation direction. The applicability and accuracy of the method is tested using integrated optic waveguide devices, namely, graded index slab waveguide. The proposed BPM uses Fourier decomposition of the transverse field. Coupled mode theory (CMT) of optical waveguides in non-homogeneous optical medium is applied to study the interaction of lightwaves propagation together such as in a DWDM system. The BPM results is verified by CMT. The inhomogeneous waveguide theory is extended to study pulse propagation in DWDM optical communication system. Nonlinear optical effects are an important aspects of DWDM systems with fiber Raman amplifier. Finite difference time domain (FDTD) method is necessary to study these nonlinear optical effects as other conventional methods are not suitable here. Here, we discuss DWDM optical communication systems due to nonlinearity in the form of SRS effect. In case of FRA, we study the various kinds of fiber profile design parameters, for the purpose to achieve and extend the flat gain bandwidth over the EDFA window. We also propose and study, a new bi-directional optical fiber transmission scheme with various constraints, using Raman amplification process with and without pump depletion. Our scheme, provides an advantage like high SNR, low pump induced noise, for long-haul communication link. We find that, there is a quite significant crosstalk and power coupling among the dense DWDM channels but earlier discussed BPM fails to account for possible interference effects among the channels. To reduce the harmful nonlinear optical effects like four wave mixing (FWM), we need to deploy a high chromatic dispersion fiber, which will ultimately lead to high pulse walk-off rate among the DWDM channels; hence for high bit rate long haul systems, walk-off effect can not be ignored. Application of FDTD provided an improved insight into the effect of GVD on stimulated Raman scattering crosstalk than different modulation techniques and line codes. It is shown through analysis that pulse walk-off phenomena may distort the data asymmetrically; especially for case of wide-band DWDM transmission system. Hence, the pulse walk-off effect should be considered in future systems containing optical amplifier. It is shown, that large walk-off rate may reduce the crosstalk among DWDM channels but tends to increase the asymmetric pulse distortion. Data may lose due to high walk-off effect. We also investigate channel addition/removal process in DWDM fiber Raman amplifier. We also demonstrate that the pulse walk-off effect tends to lead significantly to positive chirp for higher frequency channels. This feature can be exploited to overcome the chromatic dispersion effects in DWDM transmission systems. Pulse walk-off induced chirp, can be compensated by using the nonuniform fiber Bragg grating (NUFBG). The CMT due to periodic perturbation of the circular cylindrical waveguide structures is applied here. Here, we discuss the function of fiber Bragg grating as a transmission versus reflecting grating filter. We also discuss, FBG application to gain flattening of an EDFA window as well as how the group velocity dispersion (GVD) will be affected with bandwidth and coupling coefficient. We develop a new analytical technique to estimate the bandwidth of FBG based optical system. Finally, we investigate the dispersion compensation properties, pulse distortion, peak reflectivity analysis in uniform/non-uniform FBG due to an uniform/non-uniform incoming signal. More complicated refractive index profile can significantly reduce the GVD as well as side lobes intensity. Dispersion characteristic due to an arbitrary refractive index profile is discussed in details for the case of non-uniform FBG. Thus, we concluded that wide band DWDM optical communication system need to closely take into account various inhomogeneities and nonlinearities of optical fibers w.r.t. wave and pulse propagation.

CNPq, Capes e FINEP / Este trabalho descreve a produção e caracterização de guias de onda óticos em cristal de fluoreto de lítio (LiF) produzidos expondo o cristal a um feixe focalizado de um laser de femtosegundo, com o deslocamento do cristal na direção perpendicular ao eixo de propagação do feixe. A medida da emissão, sob iluminação específica, demonstra a presença de centros de cor dos tipos F2 e F3+ nas regiões do cristal expostas ao feixe focalizado do laser. As estruturas produzidas possuem incremento do índice de refração em relação ao índice de refração do cristal. Tais estruturas são caracterizadas em termos da sua morfologia usando microscopia convencional e confocal. A capacidade de guiamento de luz é investigada acoplando fontes laser com diferentes comprimentos de ondas. Os modos suportados são também analisados, bem como as perdas na propagação. A produção de guias de ondas de Bragg é testada acoplando uma fonte de luz branca e comparando seu espectro com o espectro que passa somente pelo cristal. A capacidade de guiamento das estruturas produzidas é confirmada pela análise dos perfis de campo próximo. Os guias suportam poucos modos e os incrementos de índices obtidos são da ordem de 10^-4. / This work describes the production and characterization of optical waveguides in lithium fluoride crystal (LiF) produced by exposing the crystal to a focused femtosecond laser beam, with the crystal displacement perpendicular to the beam. The measured emissions, with specific illumination, demonstrate the presence of color centers of types F2 and F+3 at the crystal regions exposed to the focused laser beam. The produced structures have increased refractive index relative to the crystal refraction index. Such structures are characterized in terms of their morphology using conventional and confocal microscopy. Their ability to guide light is investigated through coupling different laser light. The propagation modes supported by the guides are also estimated, as well as the propagation losses. The production of a Bragg grating waveguide is locked for by coupling a white light in the guides and comparing its spectrum with that passing only through the crystal. The guiding capacity of the structural changes produced is confirmed by the near-field profile analysis. The guides support few propagation modes and the obtained changes in the refractive index are in the order of 10^-4.

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.