Thesis (M.S.)--University of Nevada, Reno, 2008. / "Dec 2008." Includes bibliographical references (leaves 61-66). Online version available on the World Wide Web.

Thesis (D.Eng.) - University of St Andrews, June 2009.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1987. / Vita. Abstract. Includes bibliographical references (leaves 41-42). Also available via the Internet.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 83-89). Also available via the Internet.

Η εποχή μας χαρακτηρίζεται από πολλούς ως η ‘’Εποχή της Πληροφορίας’’ και της διακίνησης της. Η καλύτερη λύση σήμερα στα ενσύρματα μέσα μετάδοσης εμφανίζεται να είναι η οπτική ίνα η οποία εξαναγκάζει την τεχνολογία των τηλεπικοινωνιών να μεταπηδήσει από τον κόσμο των ηλεκτρονίων στον κόσμο των φωτονίων. Κατά την μετάδοση της πληροφορίας υπάρχουν όμως φαινόμενα εξασθένησης και παραμόρφωσης του σήματος. Την λύση σε αυτά τα προβλήματα καλείται να δώσει η χρήση σολιτονίων. Στην παρούσα ερευνητική εργασία δημιουργήσαμε έναν αλγόριθμο στην Fortran για να μελετήσουμε την επίδραση διάφορων τύπων διαταραχών στην διάδοση οπτικών σολιτονίων. Συγκεκριμένα πήραμε ένα θεμελιώδες σολιτόνιο αλλά και ανώτερης τάξης και μελετήσαμε την σκέδαση Raman, την αυτό-διαμόρφωση απότομων άκρων (self-steepening) και την διασπορά τρίτης τάξης ξεχωριστά ή και με συνδυασμό αυτών. Επιπλέον χρησιμοποιήσαμε ένα θεμελιώδες σολιτόνιο και για διάφορες τιμές της μιας παραμέτρου το συγκρίναμε με θεωρία. Συμπεράναμε πως η θεωρία διαταραχών προβλέπει σωστά αποτελέσματα με την εξομοίωση για μικρές τιμές των παραμέτρων. / Our era is considered to be the ‘’Era of Information’’ and of its distribution. The optimum solution for the wired communication is considered nowadays to be the fiber optic which forces the telecommunication technology to go over from electrons to photons. During the transmission of information, phenomena as the attenuation and the deformation of the signal, take place. A description of these phenomena is given through the use of Solitons. During this master thesis we built up an algorithm in program language Fortran in order to study the effect of various types of perturbations in optical Solitons. We considered a fundamental and higher-order Solitons and we studied separately the Raman scattering, self-steepening and higher-order dispersion and all together. Also we considered a fundamental Soliton and for various values of one of the three parameters we compared it with the theory expectations. We found out that for small values of the three parameters the perturbation theory provides results which are in alignment with the experiment.

Thesis (MTech (Electrical Engineering))--Peninsula Technikon, Cape Town, 1998 / The purpose of this study was to perform an investigation into advances in the field of opto-electronics and to develop a suitable lightwave sensor, for application in smart structures research. Included in the scope of this research was the theoretical development and analysis of an appropriate technology to lead to an implementation of such sensors. This project forms part of an overall plan to gain experience in optoelectronic (photonic) sensor design. In research done previously in smart structure monitoring, piezo-electric techniques with the usual electrical interconnections was used. In a highly distributed sensor system the problems of electromagnetic interference, the tribo-electric effect and noise could be problematic. In this research, opto electronic techniques were thoroughly researched and an improvement on laser based fibre-optic interferometers was made. A non monochromatic lightwave interferometer was developed from theory and a prototype tested. The results suggests that an interferometric sensor can be operated with a non monochromatic source by using a second interferometer to modulate the frequency spectrum of the light before it is detected by a photodetector. Various test and measurement circuits for improved photodetector performance were evaluated, as well as a study of signal processing techniques that would be of use for an upgrade of the project where specific feature detection and analysis using the sensor is envisaged. A specification for a computer based data acquisition system was developed to do initial tests. The project should continue, with the sensor head being improved and all the necessary signal processing routines programmed into a Labview based data acquisition system.

Thesis (DTech (Electrical Engineering))--Peninsula Technikon, Cape Town, 2002 / In the last decade, the South Amcan Electricity Supply Commission would have had their ability to serve an ever demanding public severely tested. With the dilemma of providing electricity supply through hazardous environmental conditions, and with prospects of supplying power even beyond South Afiican borders, the need for a comprehensive damage and power delivery assessment strategy becomes all the more relevant. The rapid growth being made in the evolution of so called "intelligent" structures, with inherent sensor, actuator and control mechanisms built in can have direct influence on a power distribution network. At least in the foreseeable future, the impact ofphotonic sensors with inherent miniaturization, a foremost candidate in Smart System technology, can play a vital role in damage assessment of a potentially large network such as that found in the supply ofelectricity. Smart systems are nonliving systems that integrate the functions of sensing, actuation, logic and control, to respond adaptively to changes in their condition or environment to which they are exposed, in a useful and usually repetitive manner. Sensors are a fundamental part of the evolution of such systems and form the basis for the topic of this dissertation. The use ofoptical fiber sensors is increasing widely mainly due to their (a) miniature size, (b) remote signal processing ability, and (c) multiplexing capabilities. Because of the above features a variety of optical fiber sensing techniques has evolved over the years having potential for a myriad of applications. In this work a systems model and equations was developed for modeling the propagation of light in a optical waveguide, in order to study a Fabry Perrot sensor topology for application as a miniaturised sensor in a new type of smart structure, namely a smart electrical power system.

Thesis (DTech (Mechnical Engineering))--Cape Peninsula University of Technology, 2005 / Among the issues that are taken into consideration for many years by Engineers and Technologists is the integrity of the servicing elements in structures and mechanisms. It is a documented phenomenon that after a certain period of time, in service, engineering components tend to change their original state, and begin to develop faults and defects. This includes the original shape distortion due to effects such as bending, twisting, and cracks. The above-sited effects may be caused by the sudden or accumulative effect of overloading, thermal shocks, corrosion etc, which eventually lead to malfunction of these engineering components. The occurrence of the cracks may be as a result of stress variation in excess of different or similar materials; thermal shocks, vibration, etc. A system of structural health monitoring using optical fiber sensors to track down a crack occurrence and its propagation is considered to be a promising method in warning of catastrophic events. Taking advantage of optical fibers' properties and behavior, such as easy interaction with other materials, small size, low weight, corrosion resistance, geometrical flexibility and an inherent immunity to electromagnetic interference, there is potential in adopting the Fiber Optic Sensors (FOS) for structural health monitoring systems. Structural integrity does not confine itself to crack detection only. For example there are many instances where unwanted or excessive displacement may occur. Optical fibers play an important role in proximity sensing as evidenced in the literature [49] to [54] and available commercial systems. However it is felt that FOS displacement sensors may suffer in measurement accuracy due to in situ conditions.

M.Ing. / The development of fibre optic technology as we know it today, has taken a giant leap forward since the introduction of Internet technology and other telecommunication devices. More recently, the need exists to retrieve and send huge amounts of data fast and efficiently by using fibre optic cable in computer networks, without the need of expensive equipment. Due to the large amounts of data (like video and audio) that has to be sent and received across a computer network at large distances, this dissertation is primarily concerned with the design and manufacturing of low-loss uniform long period fibre gratings for the realization of future optical add/drop multiplexers. An azimuthally symmetric manufacturing method is implemented using several optical components and devices. Several electronic devices are connected to a Mannesmann Rexroth ECODRIVE03 drive controller unit, and a computer control program was written in VISUAL BASIC 6.0 to control these devices during the manufacturing of these unique LPGs. A number of theories and numerical methods such as the coupled-mode theory and the transfer matrix method are applied in the analysis, modelling, and simulation of short/long-period fibre gratings. Simulation results were obtained in MATLAB 6.5 and the code was written in such a way that the end user could simulate any short/long-period grating and obtain the necessary results such as the transmission spectra, time delay and dispersion for uniform fibre gratings. These simulations obtained were a good indication on how the experimental results should look after manufacturing the unique symmetric LPGs.

M.Ing. (Mechanical Engineering) / The dissertation explores the applications and limitations of optic Fibre Bragg Grating (FBG) sensors for the purpose of structural health monitoring of high performance composite aerospace structures. The absence of a set of stringent performance criteria governing the form and function of a sensory system for embedded high performance applications highlights the major hurdle to be overcome before widespread acceptance of these technologies becomes apparent. The dissertation therefore develops through an extensive literature study a basic framework of performance criteria to be met by the sensory system upon which a prototype Structural Health Monitoring (SHM) system can be further developed. The resolution of the performance criteria into categories of mechanical and non-mechanical performance allows independent evaluation of factors that directly affect the performance of the sensor (in terms of strength, embeddability and load carrying ability) as well as its functional performance (in terms of orientation, spatial resolution and measurement philosophy). The literature study uses the non-mechanical performance limitations as a guideline for the selection of Fibre Bragg Grating (FBG) sensors as the sensory mechanism. The mechanical performance limitations of these specific sensors are then called into question and evaluated. Independent experiment campaigns are therefore developed to evaluate the mechanical and non-mechanical performance limitations such that a set of performance criteria can be developed governing the use of embedded sensory systems. Non mechanical performance with particular emphasis on sensor placement and orientation is investigated by simulating a fixed-free Euler Bernoulli cantilever using the Finite Element Method (FEM). The ability of the sensor to identify structural changes by measuring changes in modal response shows good results. Furthermore the inability of modal based monitoring to identify structural changes in the vicinity of modal inflection points is identified as an opportunity to locate structural deficiencies by monitoring multiple modes with known inflection point positions. The method also provides recommendations of sensor placement and orientation (close to the beam fixture and parallel with the neutral axis) such that the effectiveness of strain component measurements from all measurable modes is maximised. Mechanical performance of embedded FBG sensors is evaluated through an extensive fracture testing program which measures the fracture strains of fibre samples subjected to two-point bending. The fracture test program allows the quantification of the effects of the presence of the fibre’s protective polymer coating on fibre embeddability in composites, the consequent effects that the removal of this coating has on the mechanical performance and fracture behaviour of FBG sensors. These effects are qualified and mitigatory measures developed to improve the mechanical performance. A system of crack masking, hydrofluoric acid etching and fibre treatment is developed and statistical data analysis methods are employed and refined such that improvements in the mechanical properties of the FBG sensors can be quantified. An evaluation of the effectiveness of the proposed mechanical performance improvements yields good results culminating in the development of a comprehensive set of mechanical performance criteria to facilitate further development of a reliable SHM system.