Dissertations / Theses on the topic 'Non-imaging fiber optic system'

Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2014.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 63-65).
In this thesis, the design and implementation of a fiber optic Doppler optical coherence microscopy (FO-DOCM) system for cochlear imaging applications is presented. The use of a fiber optic design significantly reduces system size and complexity and the construction of a novel alignment and micropositioning apparatus increases ease of use for the researcher performing the imaging. To enable precise measurements of tissue motion, a time domain DOCM approach is used, utilizing an acousto-optic modulator (AOM) based optical heterodyne system to generate a stationary interference carrier frequency. By referencing this interference signal against the AOM drive signals, measurements of motions with magnitude on the order of 10 pm are shown to be possible. In addition to interferometrically measuring small amplitude motion, the FO-DOCM system is shown to be capable of imaging with a volumetric resolution of 10 x 9 x 9 pm. Demonstrative results of imaging cochlear tissue are presented by using the FO-DOCM system to image and measure motion in a guinea pig cochlea in vitro.
by Logan P. Williams.
M. Eng.

La microscopie multiphotonique est un outil essentiel d’investigation en biologie cellulaire et tissulaire. Son extension à l’endoscopie est l’objet d’intenses efforts de recherche pour des applications en neurosciences (imagerie cérébrale du petit animal) ou en clinique (diagnostic précoce, aide à la biopsie). Ce manuscrit porte sur le développement d’un endomicroscope multiphotonique présentant des performances inédites. Ce dispositif est alimenté par un oscillateur titane-saphir standard. Vient ensuite un module de pré-compensation des distorsions linéaires et non linéaires se produisant dans la fibre endoscopique. Ce module permet d’obtenir des impulsions compressées de 39 fs à la sortie d’une fibre microstructurée air-silice innovante à double gaine de 5 mètres de long qui est optimisée pour l’excitation multiphotonique (cœur central de 3,4 µm à maintien de polarisation) et la collection du signal produit par les cibles biologiques. A l’extrémité de la fibre, on trouve une sonde endoscopique, de 2,2 mm de diamètre pour 37 mm de long, composée d’un micro-scanner à fibre optique et d’un micro-objectif achromatique de distance de travail supérieure à 400 µm. La résolution spatiale de l’appareil vaut 0,83 µm et l’acquisition se fait en simultané sur deux canaux spectraux à 8 images/s. L’appareil a permis l’enregistrement d’images in vivo sans marquage des tubules et de la capsule rénale, respectivement par fluorescence à deux photons des flavines et par génération de second harmonique du collagène, avec 30 mW sur les tissus et jusqu’à 300 µm sous la surface de l’organe
Multiphoton microscopy is an essential investigative tool in cell and tissue biology. Its extension to endoscopy is the subject of intensive research for applications in neuroscience (brain imaging of small animals) or clinical (early diagnosis, help for biopsy). This manuscript focuses on the development of an endomicroscope with multiphoton unprecedented performance. This device is powered by a standard titanium-sapphire oscillator. Then comes a pre-compensation module of linear and nonlinear distortions occurring in the endoscopic fiber. This module provides compressed pulses of 39 fs at the direct output of 5 meters long innovative double-clad air-silica microstructured fiber which is optimized for multiphoton excitation (polarization maintaining central core of 3.4 µm) and the collection of the signal produced by biological targets. At the end of the fiber, there is an endoscopic probe, 2.2 mm in diameter and 37 mm long, composed of a micro fiber scanning system and an achromatic micro-objective with a working distance greater than 400 µm. The spatial resolution of the device is 0.83 µm and the acquisition is done simultaneously on two spectral channels at 8 frames/s. The device has recorded in vivo images without label of the tubules and the renal capsule, respectively by two-photon excitation fluorescence of flavins and second harmonic generation of collagen, with 30 mW on the tissues and 300 µm below the surface of the organ

Cancer is a major health problem in the world today. Almost all cancers have a significantly better chance for therapy and recovery if detected at their early stage. The capability to perform disease diagnosis at an early stage requires high-resolution imaging that can visualise the physiological and morphological changes at a cellular level. However, resolving powers of current medical imaging systems are limited to sub-millimeter sizes. Furthermore, the majority of cancers are associated with morphological and functional alterations of cells in epithelial tissue, currently assessed by invasive and time-consuming biopsy. Optical imaging enables visualisations of tissue microstructures at the level of histology in non-invasive means. Optical imaging is suitable for detecting neoplastic changes with sub-cellular resolution in vivo without the need for biopsy. Nonlinear optical microscopy based on multi-photon absorption and higher harmonic generation has provided spectacular sights into visualisation of cellular events within live tissue due to advantages of an inherent sectioning ability, the relatively deep optical penetration, and the direct visualisation of intrinsic indicators. Two-photon excited uorescence (TPEF) from intrinsic cell components and second harmonic from asymmetric supermolecular structures can provide complementary information regarding functionalities and morphologies in tissue environments, thus enabling premalignant diagnosis by detecting the very earliest changes in cellular structures. During the past sixteen years, nonlinear optical microscopy has evolved from a photonic novelty to a well-established laboratory tool. At present, in vivo imaging and long-term bedside studies by use of nonlinear optical microscopy have been limited due to the fact that the lack of the compact nonlinear optical instrument/imaging technique forces the performance of nonlinear optical microscopy with bulk optics on the bench top. Rapid developments of fibre-optics components in terms of growing functionalities and decreasing sizes provide enormous opportunities for innovation in nonlinear optical microscopy. Fibre-based nonlinear optical endoscopy will be the soul instrumentation to permit the cellular imaging within hollow tissue tracts or solid organs that are inaccessible with a conventional optical microscope. Lots of efforts have been made for development of miniaturised nonlinear optical microscopy. However, there are major challenges remaining to create a nonlinear optical endoscope applicable within internal cavities of a body. First, an excitation laser beam with an ultrashort pulse width should be delivered eciently to a remote place where ecient collection of faint nonlinear optical signals from biological samples is required. Second, laser-scanning mechanisms adopted in such a miniaturised instrumentation should permit size reduction to a millimeter scale and enable fast scanning rates for monitoring biological processes. Finally, the design of a nonlinear optical endoscope based on micro-optics must maintain great exibility and compact size to be incorporated into endoscopes to image internal organs. Although there are obvious diculties, development of fibre-optic nonlinear optical microscopy/endoscopy would be indispensible to innovate conventional nonlinear optical microscopy, and therefore make a significant impact on medical diagnosis. The work conducted in this thesis demonstrates the new capability of nonlinear optical endoscopy based on a single-mode fibre (SMF) coupler or a double-clad photonic crystal fibre (PCF), a microelectromechanical system (MEMS) mirror, and a gradientindex (GRIN) lens. The feasibility of all-fibre nonlinear optical endoscopy is also demonstrated by the further integration of a double-clad PCF coupler. The thesis concentrates on the following key areas in order to exploit and understand the new imaging modality. It has been known from the previous studies that an SMF coupler is suitable for twoii photon excitation by transmitting near infrared illumination and collecting uorescence at visible wavelength as well. Although second harmonic generation (SHG) wavelength is farther away from the designed wavelength of the fibre coupler than that of normal TPEF, it is demonstrated in this thesis that both SHG and TPEF signals can be collected simultaneously and eciently through an SMF coupler with axial resolution of 1.8 um and 2.1 um, respectively. The fibre coupler shows a unique feature of linear polarisation preservation along the birefringent axis over the near infrared and the visible wavelength regions. Therefore, SHG polarisation anisotropy can be potentially extracted for probing the orientation of structural proteins in tissue. Furthermore, this thesis shows the characterisation of nonlinear optical microscopy based on the separation distance of an SMF coupler and a GRIN lens. Consequently, the collection of nonlinear signals has been optimised after the investigation of the intrinsic trade-off between signal level and axial resolution. These phenomena have been theoretically explored in this thesis through formalisation and numerical analysis of the three-dimensional (3D) coherent transfer function for a SHG microscope based on an SMF coupler. It has been discovered that a fibreoptic SHG microscope exhibits the same spatial frequency passband as that of a fibreoptic reection-mode non-uorescence microscope. When the numerical aperture of the fibre is much larger than the convergent angle of the illumination on the fibre aperture, the performance of fibre-optic SHG microscopy behaves as confocal SHG microscopy. Furthermore, it has been shown in both analysis and experiments that axial resolution in fibre-optic SHG microscopy is dependent on the normalised fibre spot size parameters. For a given illumination wavelength, axial resolution has an improvement of approximately 7% compared with TPEF microscopy using an SMF coupler. Although an SMF enables the delivery of a high quality laser beam and an enhanced sectioning capability, the low numerical aperture and the finite core size of an SMF give rise to a restricted sensitivity of a nonlinear optical microscope system. The key innovation demonstrated in this thesis is a significant signal enhancement of a nonlinear optical endoscope by use of a double-clad PCF. This thesis has characterised properties of our custom-designed double-clad PCF in order to construct a 3D nonlinear optical microscope. It has been shown that both the TPEF and SHG signal levels in a PCF-based system that has an optical sectioning property for 3D imaging can be significantly improved by two orders of magnitude in comparison with those in an SMF-based microscope. Furthermore, in contrast with the system using an SMF, simultaneous optimisations of axial resolution and signal level can be obtained by use of double-clad PCFs. More importantly, using a MEMS mirror as the scanning unit and a GRIN lens to produce a fast scanning focal spot, the concept of nonlinear optical endoscopy based on a double-clad PCF, a MEMS mirror and a GRIN lens has been experimentally demonstrated. The ability of the nonlinear optical endoscope to perform high-resolution 3D imaging in deep tissue has also been shown. A novel three-port double-clad PCF coupler has been developed in this thesis to achieve self-alignment and further replace bulk optics for an all-fibre endoscopic system. The double-clad PCF coupler exhibits the property of splitting the laser power as well as the separation of a near infrared single-mode beam from a visible multimode beam, showing advantages for compact nonlinear optical microscopy that cannot be achieved from an SMF coupler. A compact nonlinear optical microscope based on the doubleclad PCF coupler has been constructed in conjunction with a GRIN lens, demonstrating high-resolution 3D TPEF and SHG images with the axial resolution of approximately 10 m. Such a PCF coupler can be useful not only for a fibre-optic nonlinear optical probe but also for double-clad fibre lasers and amplifiers. The work presented in this thesis has led to the possibility of a new imaging device to complement current non-invasive imaging techniques and optical biopsy for cancer detection if an ultrashort-pulsed fibre laser is integrated and the commercialisation of the system is achieved. This technology will enable in vivo visualisations of functional and morphological changes of tissue at the microscopic level rather than direct observations with a traditional instrument at the macroscopic level. One can anticipate the progress in bre-optic nonlinear optical imaging that will propel imaging applications that require both miniaturisation and great functionality.

Дисертація присвячена вирішенню наукової проблеми підвищення ефективності незображуючих волоконно-оптичних систем (НВОС) для мінімально інвазивної клінічної медицини. Розроблено узагальнені принципи структурно-функціональної організації незображуючих волоконно-оптичних систем для мінімально інвазивної клінічної медицини, в основі яких лежать узагальнені класифікації НВОС та волоконно- оптичного інструменту (ВОІ); оригінальну математичну модель розповсюдження оптичного випромінювання всередині біотанини та математичну модель флуоресцентного сигналу від неї; нові математичні моделі та технічні рішення побудови оригінальних базових функціональних модулів з оцінюванням і оптимізацією їх ефективності за запропонованими кількісними показниками з метою цілеспрямованого створення діагностичних та лікувальних систем і наступним їх впровадженням у виробництво та клінічну практику.

Beneath North America's roads lie 1.6 million miles of pipeline that provides users with potable water and carry away wastewater. These buried infrastructure systems have been functioning for duration longer than their intended design life, often with little or no repair. Asset management of pipeline systems pose a major challenge for most municipalities due to budgetary constraints, demand for quality service, and need to preserve existing pipeline infrastructure. The first step in developing and implementing a comprehensive asset management plan is to perform a condition assessment. There is a gamut of inspection and monitoring technologies available to enable the condition assessment of pipelines. All of these have advantages and limitations, which determine the performance quality and effectiveness of an individual technology for particular utility assets. Unfortunately, utilities choose technologies not suitable for their specific assets and collect data that is not useful for understanding the condition of their system. The objective of this thesis is to develop a framework for the effective selection of condition assessment technologies for water and wastewater utilities. A Microsoft-Excel based framework is developed to help the utility managers in selecting condition assessment technologies for their water and wastewater pipeline assets. The recommended tool selection approach uses a multi-step exclusion protocol in which the tools are excluded on the basis of their applicability relating to technical feasibility and technical suitability for a particular situation. Usable tools are then compared against a performance and cost database to determine performance and cost in a given project/ utility condition. This thesis provides a brief description and review of 24 non-destructive commercialized condition assessment technologies, including the principal and implementation considerations. A framework for decision system tool was developed to facilitate utilities in selecting appropriate condition assessment technologies. This framework could facilitate the selection of usable technologies by excluding the options which are not technically feasible and suitable. The user can then further explore the usable tools and determine the most suitable technologies for their assets. The data considered in the research is provided by technology providers, thus it may lack complete understanding of the capabilities and limitations of technology. This thesis also presents a case study which highlights the existing gap between the understanding of capabilities and limitations of various technologies. A program is developed as a part of this thesis, Condition Assessment Selection Tool (CAST), which consists of performance and economic database, a graphical user interface to facilitate user input, and the results of the comparison of each usable technology in the database to the project information provided by the user for their assets. The results are presented as performance indices and economic indices indicating the performance and technology cost of usable technologies. A data reliability index was also developed to provide a scale for comparing the reliability of the existing data in the database.
Master of Science

A high speed, 125 mega-bit per second data rate, data communication channel using fiber optic technology is described. Medical image data, generated by CT scanner or magnetic resonance imaging type imaging equipment, passes from standard American College of Radiology - National Electrical Manufactures Association (ACR-NEMA) interface equipment to the High Speed Fiber Optic Network Interface (HSFONI). The HSFONI implements the ACR-NEMA standard interface physical layer with fiber optics. The HSFONI accepts data from up to 8 devices and passes data to other devices or to a data base archive system for storage and future viewing and analysis. The fiber components, system level, and functional level considerations, and hardware circuit implementation are discussed.

A study of the application of single-mode fiber optics to the multiple-beam interferometric recombination problem is presented. In the laboratory, the fibers have been used in wide bandwidth, two-arm, Mach-Zehnder test interferometers as well as a 5-telescope imaging interferometer connected to an all-fiber beam combiner. Based upon these experiments and some theoretical studies it is shown that fiber optics and fiber optic components such as directional couplers provide an excellent alternative to conventional optics such as mirrors, beamsplitters, and relay lenses. The equations describing the measurement of the complex degree of coherence in an interferometer with a single-mode fiber in each arm are derived. The equations reveal an important feature of the fibers: they filter phase fluctuations due to aberrations and turbulence at the input and convert them to intensity fluctuations at the output. This leads to a simplification of the calibration of measured visibilities. The coupling efficiency of light which has passed through a turbulent atmosphere is also studied as a function of fiber parameters and turbulence conditions for both image motion stabilized and non-stabilized cases. For the former case, coupling efficiency remains greater than 50% as long as telescope diameter is no larger than the turbulence coherence length. Beam combination architectures using arrays of directional couplers are fully discussed. Arrays accommodating up to 20 input beams are presented. The arrays require only N detector pixels for N input beams. A scheme of temporal multiplexing of the phase of each beam is used to identify individual fringe pairs. One possible scheme allows wide bandwidths even for large numbers of beams. A 5-telescope interferometer has been constructed and connected to an all-fiber beam combiner. Two extended objects were observed and reconstructed using standard radio astronomy VLBI software. The interferometer and beam combiner had good thermal and polarization stability and high throughput. Reconstructed images had dynamic ranges of about 50.

Bioengineering
Ph.D.
More than 350,000 anterior cruciate ligament (ACL) injuries occur every year in the United States. A torn ACL is typically replaced with an allograft or autograft tendon (patellar, quadriceps or hamstring), with the choice of tissue generally dictated by surgeon preference. Despite the number of ACL reconstructions performed every year, the process of ligamentization, transformation of a tendon graft to a healthy functional ligament, is poorly understood. Previous research studies have relied on mechanical, biochemical and histological studies. However, these methods are destructive. Clinically, magnetic resonance imaging (MRI) is the most common method of graft evaluation, but it lacks adequate resolution and molecular specificity. There is a need for objective methodology to study the ligament repair process that would ideally be non- or minimally invasive. Development of such a method could lead to a better understanding of the effects of therapeutic interventions and rehabilitation protocols in animal models of ligamentization, and ultimately, in clinical studies. Fourier transform infrared (FT-IR) spectroscopy is a technique sensitive to molecular structure and composition in tissues. FT-IR fiber optic probes combined with arthroscopy could prove to be an important tool where minimally invasive tissue assessment is required, such as assessment of graft composition during the ligamentization process. Spectroscopic methods have been used to differentiate normal and diseased connective tissues, but have not been applied to investigate ligamentization, or to investigate differences in tendons and ligaments. In the proposed studies, we hypothesize that infrared spectroscopy can provide molecular information about the compositional differences between tendons and ligaments, which can serve as a foundation to non-destructively monitor the tissue transformation that occurs during ligamentization.
Temple University--Theses

In recent years, a growing number of diagnostic examinations in a hospital are being generated by digitally formatted imaging modalities. The evolution of these systems has led to the development of a totally digitized imaging system, which is called Picture Archiving and Communication System (PACS). A high speed computer network plays a very important role in the design of a Picture Archiving and Communication System. The computer network must not only offer a high data rate, but also it must be structured to satisfy the PACS requirements efficiently. In this dissertation, a computer network, called PACnet, is proposed for PACS. The PACnet is designed to carry image, voice, image pointing overlay, and intermittent data over a 200 Mbps dual fiber optic ring network. The PACnet provides a data packet channel and image and voice channels based on Time Division Multiple Access (TDMA) technique. The intermittent data is transmitted over a data packet channel using a modified token passing scheme. The voice and image pointing overlay are transferred between two stations in real-time to support the consultive nature of a radiology department using circuit switching techniques. Typical 50 mega-bit images are transmitted over the image channel in less than a second using circuit switching techniques. A technique, called adaptive variable frame size, is developed for PACnet to achieve high network utilization and short response time. This technique allows the data packet traffic to use any residual voice or image traffic momentarily available due to variation in voice traffic or absence of images. To achieve optimal design parameters for network and interfaces, the PACnet is also simulated under different conditions.

This paper describes the design and simulation of a network interface unit (NIU) for a picture archiving and communication system (PACS) network called PACnet. PACnet is a dual fiber optic ring network under development at the Computer Engineering Research Laboratory of the University of Arizona. This network integrates voice, data, and image communications in a hospital environment and supports a throughput rate between 200-500 megabits per second. At each node in the network, an NIU implements the Data Link Layer and Physical Layer protocols of PACnet. The initial network interface unit design for PACnet was a functional description of NIU protocols and major components. In order to construct a demonstration prototype of PACnet,the NIU description must be refined and an architecture must be specified. The NIU design is specified and simulated using the hardware description language VHDL. Simulation results provide information on NIU timing characteristics and logic families required to implement the NIU.

Ces travaux de thèse présentent l’étude des différentes classes d’effets linéaires et non-linéaires en optiquequi génèrent des événements extrêmes dont les propriétés sont analogues à celles des « vagues scélérates » destructrices qui apparaissent à la surface des océans. La thèse commence avec un bref aperçu de l’analogie physique entre la localisation d’onde dans les systèmes hydrodynamique et les systèmes optique, pour lesquels nous décrivons les mécanismes de génération de vagues scélérates linéaire et non-linéaire. Nous présentons ensuite quelques résultats numérique et expérimentaux de la génération de vagues scélérates dans un système optique linéaire dans le cas d’une propagation spatiale d’un champ optique qui présenteune phase aléatoire, où nous interprétons les résultats obtenus en terme de caustiques optiques localisées.Nous considérons ensuite les vagues scélérates obtenues dans des systèmes non-linéaires qui présentent une instabilité de modulation décrite par l’équation de Schrödinger non-linéaire (ESNL). Nous présentons une étude numérique détaillée comparant les caractéristiques spatio-temporelles des structures localisées obtenues dans les simulation numérique avec les différentes solutions analytiques obtenues à partir de l’ESNL.Deux études expérimentales d’instabilités de modulation sont ensuite effectuées. Dans la première, nous présentons des résultats expérimentaux qui étudient les propriétés d’instabilité de modulation en utilisant un système d’agrandissement temporel par lentille temporelle; dans la deuxième, nous rapportons des résultats expérimentaux sur les propriétés des instabilités de modulation dans le domaine fréquentiel en utilisant une technique de mesure spectrale en temps-réel. Cette dernière étude examine l’effet sur la bande spectrale et surla stabilité d’un faible champ perturbateur. Tous les résultats expérimentaux sont comparés avec la simulation d’ESNL et abordés en termes des propriétés qualitatives d’instabilité de modulation. Dans toutes ces études,différentes propriétés statistiques sont analysées en rapport avec l’apparition des vagues scélérates
This thesis describes the study of several different classes of linear and nonlinear effects in optics that generatelarge amplitude extreme events with properties analogous to the destructive “rogue waves” on the surface of theocean. The thesis begins with a brief overview of the analogous physics of wave localisation in hydrodynamicand optical systems, where we describe linear and nonlinear rogue wave generating mechanisms in bothcases. We then present numerical and experimental results for rogue wave generation in a linear opticalsystem consisting of free space propagation of a spatial optical field with random phase. Computed statisticsbetween experiment and modelling are in good agreement, and we interpret the results obtained in termsof the properties of localised optical caustics. We then consider rogue waves in the nonlinear system ofmodulation instability described by the Nonlinear Schrodinger Equation (NLSE), and a detailed numericalstudy is presented comparing the spatio-temporal characteristics of localised structures seen from numericalsimulations with different known analytic solutions to the NLSE. Two experimental studies of modulationinstability are then reported. In the first, we present experimental results studying the properties of modulationinstability using a time-lens magnifier system; in the second, we report experimental results studying thefrequency-domain properties of modulation instability using real-time spectral measurements. The latter studyexamines the effect of a weak seed field on spectral bandwidth and stability. All experimental results arecompared with the NLSE simulations and discussed in terms of the qualitative properties of modulationinstability, in order to gain new insights into the complex dynamics associated with nonlinear pulse propagation.In all of these studies, different statistical properties are analised in relation to the emergence of rogue waves

Bien que l’avantage principal des communications optiques est de permettre la transmission des capacités élevées en multiplexant les longueurs d’onde, le traitement des données, par exemple en vue de régénération ou de routage, doit être effectué dans le domaine électrique, nécessitant ainsi des conversions optique-électrique-optique. Cependant, certaines fonctions de traitement pourraient être effectuées plus efficacement directement dans le domaine optique, ce qui est connu par le traitement de signal tout-optique. Comme des nouvelles techniques exploitant la dimension spatiale dans les fibres multimodes ont été proposées afin d'augmenter la capacité de transmission, une meilleure compréhension des effets non linéaires associés aux interactions multimodes est donc souhaitable. Cette thèse visait à explorer le traitement du signal tout-optique dans le multiplexage modal. En particulier, l'objectif était de démontrer comment les effets non linéaires dans les fibres multimodes pouvaient être utilisés pour manipuler les propriétés des signaux, de manière indépendante ou dépendante du mode. Deux types de fibres ont été conçus. La première permet de réaliser certaines fonctions de traitement de signal tout-optique pour tous les modes de la fibre individuellement et simultanément, en utilisant l'effet non linéaire mélange à quatre ondes intramodal. La deuxième fibre a été conçue de manière à réaliser du traitement de signal tout-optique entre différents modes de la fibre, en utilisant le mélange à quatre ondes intermodal
While the main advantage of optical communications is to enable transmission of ultra-high capacities by multiplexing dozens of wavelength channels operating at high bit rates, the processing of the data, for instance in view of its regeneration or routing, needs to be performed in the electrical domain, thus requiring optical-to-electrical-to-optical conversions. However, some processing functionalities could be performed more efficiently directly in the optical domain, which is known as all-optical signal processing. As new techniques exploiting the spatial dimension in multimode fibers have been proposed in order to further increase the transmitted capacity, a better understanding of nonlinear effects associated with multimode interactions is desirable. This thesis aimed to explore paths for all-optical signal processing in modedivision multiplexing. In particular, the target was to demonstrate how nonlinear effects in multimode fibers could be used to manipulate the properties of optical signals, either in a mode independent way, or mode dependent way. Two types of fibers were designed. The first one allows to perform some all-optical signal processing functionalities for all the modes of the fiber individually and simultaneously, by using the intramodal fourwave mixing nonlinear effect. The second fiber was designed in a way to perform all-optical signal processing between different modes of the fiber, using intermodal four-wave mixing

Les méthodes de mesure optiques sont très performantes avec une sensibilité et une résolution généralement supérieure aux autres techniques, et elles possèdent aussi l’avantage d’être sans contact et non invasives. Cette thèse introduit plusieurs nouvelles techniques de détection optique et d'imagerie basées sur l’utilisation de sources super continuum dans l’infrarouge.Les propriétés uniques de ce type de source lumineuse, en particulier leur large bande spectrale combinée à une cohérence spatiale parfaite,permettent d’obtenir des performances supérieures en terme de résolution ou de sensibilité.Les techniques proposées sont expérimentalement démontrées et leurs performances caractérisées.La thèse démontre une technique de spectroscopie par absorption en cavité résonnante ainsi qu’une technique de spectroscopie par effet photo-acoustique, pour la première fois dans l’infrarouge moyen. La thèse introduit un nouveau concept de détection et d'imagerie par corrélations,équivalent à l’imagerie fantôme mais dans le domaine spectral, et son application à la spectroscopie par absorption ainsi qu'à la tomographie par cohérence optique d'objets physiques sont démontrées. Les techniques proposées et étudiées dans cette thèse ouvrent de nouvelles perspectives pour la détection sensible et l’imagerie dans l’infrarouge. De manière plus générale,les concepts introduits étant génériques, ils peuvent être étendus à d’autres régions du spectre électromagnétique et les travaux présentés sont amenés à stimuler de nouvelles idées et de nouveaux développements pour les techniques de détection et d'imagerie optiques
The ability to detect substances or molecules with high sensitivity and to image objects with high resolution plays an important role in our everyday life as well as in advances in understanding fundamental phenomena. Optical techniques are generally highly beneficial for this purpose as they are intrinsically remote, non-invasive and exhibit superior sensitivity and resolution. In this context, it is thus not surprising that a wide range of sensing and imaging techniques have been developed in the past decades and are continuously the subject intense research. The performance of these methods depends dramatically on the type of light source that is used and it is therefore essential to tailor the light source properties to the intended method of application.A spectral region which has recently attracted a wide interest is the mid-infrared corresponding to the molecular fingerprint region and the atmospheric transparency window. This in turn has triggered renewed research effort into adapting existing technique to this particular region of the electromagnetic spectrum including the light sources and detection schemes. This thesis reports novel, proof-of-concept, broadband optical sensing and imaging techniques in the infrared using supercontinuum light, a class of light sources with unique properties. The techniques are experimentally demonstrated and their performances discussed.Specifically, the thesis demonstrate incoherent broadband cavity enhanced absorp- tion spectroscopy in the mid-infrared wavelength range from 3000 to 3450 nm. Multi-component gas detection with sub-ppm accuracy is achieved in this range, which constitutes the widest continuous detection range for this technique in the mid-infrared.Cantilever-enhanced photoacoustic spectroscopy in the mid-infrared is also demonstrated for the first time in this thesis. The approach is broadband and allows for higher photoacoustic signal intensity and enhanced signal-to-noise ratio as compared to conventional systems that use back-body radiation sources. These results offer novel perspective for photoacoustic detection opening the door to sensitive broadband and compact analysers in the mid-infrared spectral region.Exploiting the shot-to-shot fluctuations of an incoherent supercontinuum and the recent progress in ultrafast real-time spectral measurement techniques, the thesis finally reports on a novel proof-of-concept correlation sensing and imaging method in the form of spectral-domain ghost imaging. The method is fast, scan-free, and offer new opportunities for remote sensing in scattering and absorbing media, or in spectral regions where sensitive detectors are lacking. Application of this technique to broadband spectroscopic measurements gases as well as for interferometric imaging of physical objects is demonstrated. One can legitimately expect that the work presented in this thesis will foster new ideas and developments for optical sensing and imaging

Ce manuscrit de thèse présente l’étude d’instabilités non-linéaires et la génération d’ondes scélérates complexes liées à la propagation de la lumière dans des fibres optiques standards des télécommunications optiques. Un rappel est tout d’abord présenté sur les phénomènes physiques linéaires et non-linéaires impliqués et qui peuvent présenter une analogie directe avec le domaine de l’hydrodynamique. Les différentes formes d’ondes scélérates liées au processus d’instabilité de modulation, aussi appelées « breathers », sont alors présentées, elles sont obtenues par la résolution de l’équation de Schrödinger non-linéaire. À partir de ces solutions exactes, divers systèmes expérimentaux sont alors conçus par simulation numérique à partir de deux méthodes d’excitation d’ondes scélérates. La première est une génération exacte à partir des solutions analytiques en effectuant une mise en forme spectrale en intensité et en phase d’un peigne de fréquence optique. La seconde méthode est basée sur des conditions initiales approchées avec des ondes continues modulées sinusoïdalement. Les mesures expérimentales réalisées avec ces deux méthodes démontrent parfaitement la génération d’ondes scélérates complexes (solutions d’ordre supérieur du système) issues de la superposition non-linéaire ou collisions de « breathers » de premier ordre. Enfin, nous avons également étudié un système non-linéaire équivalent au modèle de Manakov, qui fait intervenir la propagation de deux ondes distinctes avec des polarisations orthogonales dans une fibre optique. L’analyse de stabilité et des simulations numériques de ce système multi-variable mettent en évidence un nouveau régime d’instabilité de modulation vectorielle ainsi que de nouvelles solutions d’ondes scélérates noires et couplées en polarisation. Un nouveau système expérimental mis en place a permis de confirmer ces prédictions théoriques avec un excellent accord quantitatif
This manuscript presents the generation of complex rogue waves related to nonlinear instabilities occurring through the propagation of light in standard optical fibers. Linear and nonlinear physical phenomena involved are first listed, in particular some of them by analogy with the field of hydrodynamics. The different forms of rogue waves induced by the modulation instability process are then presented. They are also known as "breathers", and they are obtained by solving the nonlinear Schrödinger equation. From these exact solutions, various experimental systems were designed by means of numerical simulations based on two rogue-wave excitation methods. The first one is an exact generation of mathematical solutions based on the spectral shaping of an optical frequency comb. The second method uses approximate initial conditions with a simple sinusoidal modulation of continuous waves. For both cases, experimental measurements demonstrate the generation of complex rogue waves (i.e., higher-order solutions of the system) arising from the nonlinear superposition or collision of first-order breathers. Finally, we also studied a nonlinear fiber system equivalent to the Manakov model, which involves the propagation of two distinct waves with orthogonal polarizations. The stability analysis and numerical simulations of this multi-component system highlight a novel regime of vector modulation instability and the existence of coupled dark rogue-wave solutions. A new experimental system setup was conceived and theoretical predictions are confirmed with an excellent quantitative agreement

碩士
國立陽明大學
生醫光電研究所
105
Laser Speckle Contrast Imaging (LSCI) is one of the optical technologies that can visualize blood flow in the imaging field. Simple optical setup and free of contrast agents have made LSCI a popular tool for many studies ,such as vascular structure and hemodynamics. Starting from the Free Space, this thesis verified the relationship between the flow rate and laser speckle contrast, step by step, and the optimal exposure time parameter in the hardware architecture using phantom. Then we verified the “Relative Temporal Minimum Reflectance” and the relationship between the exposure time and the flow rate. Finally, animal experiments were used to verify the parameters in phantom study are appropriate or not. After that, the use of an optical fiber structure was proposed, which can make the laser speckle contrast imaging into a simple system, and not limited to measure the small animal using anesthesia, and ultimately can be applied to monitor the hemodynamics neural in awake, moving animals. At present, we can not obtain an optimized image in the Fiber Bundle System. The mesh pattern of the fiber bundle itself will affect the calculation of the laser contrast. Finally, we refer to the method Cell erasure, but still can not get the best image. We speculate that the single fiber in the fiber bundle may be too thick or the number of effective fibers in the fiber is not enough.

碩士
國立臺北科技大學
製造科技研究所
106
This study demonstrate a imaging method by using fiber to achieve fiberize photoacoustic imaging (PAI). The imaging system primarily consists of a 532 nm fiber laser source with a high pulse repetition rate of up to 600kHz combined with a dual-axis galvanometer mirror. A laser beam is reflected by a beam splitter onto a high speed photodiode to generate trigger signals for a data acquisition card (PXI-5152, National Instruments) and another side is reflected to dual-axis galvanometer mirror to do scanning. For the confocal and coaxial ability of the optical excitation and ultrasonic detection, we use laser through fiber to generate and the Confocal Photoacoustic Transducer (CPT) to detect. Laser radiate in the fiber with the theory of total reflection. The incident is greater than the critical angle, only the incident angle in some range the laser can coupler to the fiber totally. The CPT manufacturing is cooperated with Japanese Professor Tanabe, they help us made the CPT and we do the experiment. Further, a PZT piezoelectric film is coated on a customized stainless steel substrate is applied in photoacoustic imaging. This CPT has a good axial and lateral resolution because of the outstanding focus ability. With the OR-PAM system, the image of copper wire with diameter 100μm and the vessel with width 100μm in the chicken testicle and chicken heart are successfully reconstructed in a 1x1mm2 field of view (FOV).

A previously designed lens system is constructed and characterized for possible application to engine diagnostics and 3D reconstructions of combusting flows. Since optical engines cannot be operated at the same conditions as a production engine, optical access to a production engine, with minimum changes in the engine geometry is necessary for developing a better understanding of the in-cylinder processes. The application of a probe designed to fit in the pressure transducer port of a diesel engine was demonstrated in this work. Measurement of various optical parameters established the ability of the lens system to have a good resolution over the entire stroke length of the cylinder. The temperature analysis of the probe and lens system confirmed its ability to withstand the high-temperature conditions in the engine cylinder head. The lens system design was coupled with imaging fibers to transmit images from the image plane of the probe to a high-speed camera located at a safe distance from the combusting environment. Due to the robust design of the probe and its compatibility with an imaging fiber, the probe was identified to be a good alternative as an inexpensive lens system for tomography in challenging environments. To validate its use, 3D reconstruction of a sewing pin using a range of views was demonstrated. Parameters affecting the reconstructions were identified and optimized to obtain high-quality reconstructions.

PURPOSE. To image the fundus non-invasively at two different penetration depths using a multispectral imaging system. Monochromatic images at visible spectrum wavelengths and near-infrared wavelengths were qualitatively assessed for choroidal visibility. These images were used calculate oxygen saturation in retinal tissue, optic nerve head tissue, vein, and choroidal tissue in healthy controls and glaucoma patients. METHODS. A fundus camera-based multispectral snapshot oximeter imaged the fundus of healthy subjects and patients with varying ophthalmological pathology. The images of healthy controls and glaucoma patients were analyzed to determine oxygen saturation in the optic nerve head cup and rim, superficial and deep vein, macula and choroidal tissue. RESULTS. Visible: Average oxygen saturation for the ONH cup was 65 ± 6 percent for healthy controls and 61 ± 10 percent for glaucoma patients. For the ONH rim, it was 67 ± 3 percent for healthy controls and 64 ± 17 percent for glaucoma patients. For the vein, it was 67 ± 15 percent for healthy controls and 56 ± 22 percent for glaucoma patients. For the macula, it was 87 ± 10 percent for healthy controls and 93 ± 1 percent for glaucoma patients. NIR: The average oxygen saturation for the vein was 66 ± 20 percent for healthy controls, 58 ± 0.4 percent for glaucoma suspects and 54 ± 17 percent for glaucoma patients. For the choroidal tissue below the macula, it was 99 ± 5 percent in healthy controls and 81 ± 8 percent in glaucoma patients. CONCLUSIONS. Choroidal visibility is enhanced in near infrared monochromatic images from visible spectrum monochromatic images. Oxygen saturation results were lower in glaucoma patients for all anatomical areas analyzed except the avascular macula.
acase@tulane.edu

Optics are a powerful probe of chemical structure that can often be linked to theoretical predictions, providing robustness as a measurement tool. Not only do optical interactions like second harmonic generation (SHG), single and two-photon excited fluorescence (TPEF), and infrared absorption provide chemical specificity at the molecular and macromolecular scale, but the ability to image enables mapping heterogeneous behavior across complex systems such as biological tissue. This thesis will discuss nonlinear and linear optics, leveraging theoretical predictions to provide frameworks for interpreting analytical measurement. In turn, the causal mechanistic understanding provided by these frameworks will enable structurally specific quantitative tools with a special emphasis on application in biological imaging. The thesis will begin with an introduction to 2nd order nonlinear optics and the polarization analysis thereof, covering both the Jones framework for polarization analysis and the design of experiment. Novel experimental architectures aimed at reducing 1/f noise in polarization analysis will be discussed, leveraging both rapid modulation in time through electro-optic modulators (Chapter 2), as well as fixed-optic spatial modulation approaches (Chapter 3). In addition, challenges in polarization-dependent imaging within turbid systems will be addressed with the discussion of a theoretical framework to model SHG occurring from unpolarized light (Chapter 4). The application of this framework to thick tissue imaging for analysis of collagen local structure can provide a method for characterizing changes in tissue morphology associated with some common cancers (Chapter 5). In addition to discussion of nonlinear optical phenomena, a novel mechanism for electric dipole allowed fluorescence-detected circular dichroism will be introduced (Chapter 6). Tackling challenges associated with label-free chemically specific imaging, the construction of a novel infrared hyperspectral microscope for chemical classification in complex mixtures will be presented (Chapter 7). The thesis will conclude with a discussion of the inherent disadvantages in taking the traditional paradigm of modeling and measuring chemistry separately and provide the multi-agent consensus equilibrium (MACE) framework as an alternative to the classic meet-in-the-middle approach (Chapter 8). Spanning topics from pure theoretical descriptions of light-matter interaction to full experimental work, this thesis aims to unify these two fronts.