This work encompasses a study of fibre optic devices and micro-resonator cavities and their use as strain sensors, interferometers, and eventually as light sources. We demonstrate the use of a pi-shifted fibre Bragg grating as a strain sensor and quantify its performance through several metrics relevant to its operation in a frequency-locked system. We then discuss the use of waveguide devices as refractive index sensors in a detailed and critical analysis of most of the literature on fibre optic-based interferometry where we define new metrics of assessment that are aimed to be device-independent. We then categorize and study the performance of the literature on fiber-optic refractive index sensors and highlight few key devices of each category based on their performance or design. We relate the performance of these interferometers to various design parameters to outline a way for future researchers to create high-performance devices. Finally, we study light emission in dye-loaded droplet micro-resonators, which are a promising new platform to generate low-threshold lasing action excited by lasers coupled to the whispering gallery modes of the resonator. We characterize multiple types of emissions in these cavities and pave the way for future microdroplet-based lasers. / Graduate / 2022-08-10

This thesis is based on a research project to monitor the temperature profile along a power cable using the fibre optic Distributed Temperature Sensing (DTS) technology. Based on the temperature measured by a DTS system, real time condition monitoring of power cables can be achieved. In this thesis, there are three main research themes. 1. Develop a DTS system for industrial applications. The entire hardware system and measuring software are developed to be an industrial product. Multiple functions are provided for the convenience of users to conduct temperature monitoring, temperature history logging and off-line simulation. 2. Enhance the robustness of the DTS system. An algorithm for signal compensation is developed to eliminate the signal fluctuation due to disturbance from the hardware and its working environment. It ensures robustness of the system in industrial environments and applicability to different system configurations. 3. Improve the accuracy of the DTS system. A calibration algorithm based on cubic spline fitting is developed to cope with non-uniform fibre loss in the system, which greatly improved the accuracy of the temperature decoding in real applications with unavoidable nonlinear characteristics. The developed DTS system and the algorithms have been verified by continuous experiments for about one year and achieved a temperature resolution of 0.1 degree Celsius, a spatial resolution of 1 meter, and a maximum error of 2 degree Celsius in an optic fibre with the length of 2910 metres.

One of the major purposes of this project was to demonstrate optical components which will be used in fibre optic distribution systems. These include the fibre itself, couplers, connectors, splices, sources and detectors. All components used are state-of-the-art, the star coupler and fusion splice technique being developed by the author during the completion of the project. The star coupler has proved to have one of the lowest insertion losses of any such component to date. Although the telephone system demonstrated has only 3 stations, very similar or identical components would be used in an expanded network. / Thesis / Master of Engineering (MEngr)

Structural Health Monitoring (SHM) is a helpful tool for engineers in order to control and verify the structural behaviour. SHM also guides the engineers and owners of structures in decision making concerning the maintenance, economy and safety of structures. Sweden has not a very sever tradition in monitoring, as countries with strong seismic and/or aerodynamic activities. Anyway, several large scale monitoring projects have taken place in recent years and SHM is slowly making entrance as an essential implement in managing structures by engineers as well as owners. This licentiate thesis presents a state-of-the art-review of health monitoring activities and over sensory technologies for monitoring infrastructure constructions like bridges, dams, off-shore platforms, historical monuments etc. related to civil engineering. The fibre optic equipment is presented with special consideration. The permanent monitoring system of the New Årsta Bridge consists of 40 fibre optic sensors, 20 strain transducers, 9 thermocouples, 6 accelerometers and one LVDT. The aims of the static study are: to control the maximal strains and stresses; to detect cracking in the structure; to report strain changes under construction, testing period and in the coming 10 years; and to compare conventional system with fibre optic system. The system installation started in January 2003 and was completed October 2003. The measurements took place from the very beginning and are suppose to continue for at least 10 years of operation. At the construction phase the measurements were performed manually and later on automatically through broad band connection between the office and central data acquisition systems located inside the bridge. The monitoring project of the New Årsta Railway Bridge is described from the construction phase to the testing phase of the finished bridge. Results of the recorded statistical data, crack detection and loading test are presented and a comparison between traditional techniques like strain transducers and fibre optic sensors is done. Various subjects around monitoring and sensor technologies that were found under the project are brought up in order to give the reader a good understanding, as well of the topics, techniques and of the bridge. Example of few applications is given with the aim of a deeper insight into monitoring related issues. / QC 20101112

Structural Health Monitoring (SHM) with emerging technologies like e.g. fibre optic sensors, lasers, radars, acoustic emission and Micro Electro Mechanical Systems (MEMS) made an entrance into the civil engineering field in last decades. Expansion of new technologies together with development in data communication benefited for rapid development. The author has been doing research as well as working with SHM and related tasks nearly a decade. Both theoretical knowledge and practical experience are gained in this constantly developing field. This doctoral thesis presents lessons learned in SHM and sensory technologies when monitoring civil engineering structures, mostly bridges. Nevertheless, these techniques can also be used in most applications related to civil engineering like dams, high rise buildings, off-shore platforms, pipelines, harbour structures and historical monuments. Emerging and established technologies are presented, discussed and examples are given based on the experience achieved. A special care is given to Fibre Optic Sensor (FOS) technology and its latest approach. Results from crack detection testing, long-term monitoring, and sensor comparison and installation procedure are highlighted. The important subjects around sensory technology and SHM are discussed based on the author's experience and recommendations are given. Applied research with empirical and experimental methods was carried out. A state-of-the art-review of SHM started the process but extensive literature studies were done continuously along the years in order to keep the knowledge up to date. Several SHM cases, both small and large scale, were carried out including sensor selection, installation planning, physical installation, data acquisition set-up, testing, monitoring, documentation and reporting. One case study also included modification and improvement of designed system and physical repair of sensors as well as two Site Acceptance Tests (SATs) and the novel crack detection system testing. Temporary measuring and testing also took place and numerous Structural Health Monitoring Systems (SHMSs) were designed for new bridges. The observed and measured data/phenomena were documented and analysed.  Engineers, researchers and owners of structures are given an essential implement in managing and maintaining structures. Long-term effects like shrinkage and creep in pre-stressed segmental build bridges were studied. Many studies show that existing model codes are not so good to predict these long-term effects. The results gained from the research study with New Årsta Railway Bridge are biased be the fact that our structure is indeed special. Anyhow, the results can be compared to other similar structures and adequately used for the maintenance planning for the case study. A long-term effect like fatigue in steel structures is a serious issue that may lead to structural collapse. Novel crack detection and localisation system, based on development on crack identification algorithm implemented in DiTeSt system and SMARTape delamination mechanism, was developed, tested and implemented. Additionally, new methods and procedures in installing, testing, modifying and improving the installed system were developed. There are no common procedures how to present the existing FOS techniques. It is difficult for an inexperienced person to judge and compare different systems. Experience gained when working with Fibre Optic Sensors (FOS) is collected and presented. The purpose is, firstly to give advice when judging different systems and secondly, to promote for more standardised way to present technical requirements. Furthermore, there is need to regulate the vocabulary in the field. Finally, the general accumulated experience is gathered. It is essential to understand the complexity of the subject in order to make use of it. General trends and development are compared for different applications. As the area of research is wide, some chosen, specific issues are analysed on a more detailed level. Conclusions are drawn and recommendations are given, both specific and more general. SHMS for a complex structure requires numerous parameters to be measured. Combination of several techniques will enable all required measurements to be taken. In addition, experienced specialists need to work in collaboration with structural engineers in order to provide high-quality systems that complete the technical requirement. Smaller amount of sensors with proper data analysis is better than a complicated system with numerous sensors but with poor analysis. Basic education and continuous update for people working with emerging technologies are also obligatory. A lot of capital can be saved if more straightforward communication and international collaboration are established: not only the advances but also the experienced problems and malfunctions need to be highlighted and discussed in order not to be repeated. Quality assurance issues need to be optimized in order to provide high quality SHMSs. Nevertheless, our structures are aging and we can be sure that the future for sensory technologies and SHM is promising. The final conclusion is that an expert in SHM field needs wide education, understanding, experience, practical sense, curiosity and preferably investigational mind in order to solve the problems that are faced out when working with emerging technologies in the real world applications.  The human factor, to be able to bind good relationship with workmanship cannot be neglected either. There is also need to be constantly updated as the field itself is in continuous development. / QC 20111117 / SHMS of the New Årsta Railway Bridge

The research carried out here employed analytical and imaging transmission electron microscopy and scanning transmission electron microscopy to gain a good understanding of local structure and composition of semiconductor nanocrystals and quantum dots for electronics and optoelectronics applications. One of the world's most advanced analytical scanning transmission electron microscopes in the field, the Daresbury SuperSTEM, was used to scrutinise the structure and composition of the samples. Three nanostructure systems are investigated in this thesis: 1. Structures consisting of Ge-nanocrystals (NCs) in alumina. Here HRTEM suggests relaxed and twinned smaller NCs grown annealed at lower temperature compared to elongated non-faulty bigger NCs annealed at higher temperature. HRTEM also suggests a polycrystalline structure of the matrix. 2. With regards to the InAs/GaAs quantum dots (QD) the study aims in particular at elucidating QD formation by investigating samples grown with and without growth interrupt (GI). Diffraction contrast TEM shows formation of buried dots in the sample prepared with GI whereas for the sample without GI the immediate growth of GaAs after InAs inhibits diffusion and segregation of In adotoms, and no footprint of buried dots has been observed. HRTEM and HAADF show coherent QDs in the sample with GI and abrupt InAs/GaAs interfaces in the sample without GI. In executing energy electron loss spectroscopy (EELS) and geometric phase analysis (GPA) the distribution of In in InGaAs/GaAs QDs has been obtained in samples grown in the critical thickness regime for quantum dot formation. The highest In percentage achieved in the dots grown with a nominal fraction of 100% was ~70%. EELS shows variations in the In concentration within the QD structure and wetting layer 3. In the case of Er-doped Si-NCs in silica this research tries to provide an understanding of structure, composition and position of excess Si and Er in the silica matrix of materials prepared under different growth conditions and to correlate this information with the PL emission, all with the aim to find preparation routes for optimum optical efficiency for applications of this materials system in silicon photonics. High spatial correlation between Si-NCs, Er and O in the Er and Si co-implanted sample with strong indication of an Er-oxide/Si core-shell structure had been found. The lack of an Er-oxide plasmon indicates, however, that the shell structure and its interface with the SiNCs is highly defective and a likely cause for non-radiative recombination. The sample with similar excess Er and Si concentrations but prepared in a two-stage implantation and annealing process shows a 10 times improvement in the optical emission. Here no spatial correlation between Er and Si-NCs was found in core loss EELS. EELS and HAADF evidenced more highly, near-atomically dispersed Er in the matrix with no formation of a core-shell structure as compared to the co-implanted sample. No footprint of Er-silicide plasmon was observed by low loss valence band EELS investigation in the co-implanted sample.

The work deals with dispersive effects of single mode fibers. We learn about the chromatic dispersion, the main attention is paid to the Polarization Mode Dispersion. We clarify the root cause origin of the Polarization Mode Dispersion describing parameters and its effect on transmitted data. Further on, the works dedicates to measure methods of the Polarization Mode Dispersion which is the interferometric method or the POTDR method. We explain the ways of the PMD removal at contemporary optic routes and options of PMD compensation by using compensators of various types. There is also mentioned the possibility of profiting from the soliton transmission. The last chapter deals with measuring of a real optic route. It includes measured data and its evaluation due to the ITU-T demands.

This thesis considers the problem of calculating and observing the mixing of modes of positive and negative frequency in inhomogeneous, dispersive media. Scattering of vacuum modes of the electromagnetic field at a moving interface in the refractive index of a dielectric medium is discussed. Kinematics arguments are used to demonstrate that this interface may, in a regime of linear dispersion, act as the analogue of the event horizon of a black hole to modes of the field. Furthermore, a study of the dispersion of the dielectric shows that five distinct configurations of modes of the inhomogeneous medium at the interface exist as a function of frequency. Thus it is shown that the interface is simultaneously a black- and white-hole horizon-like and horizonless emitter. The role, and importance, of negative-frequency modes of the field in mode conversion at the horizon is established and yields a calculation of the spontaneous photonic flux at the interface. An algorithm to calculate the scattering of vacuum modes at the interface is introduced. Spectra of the photonic flux in the moving and laboratory frame, for all modes and all realisable increase in the refractive index at the interface are computed. As a result of the various mode configurations, the spectra are highly structured in intervals with black-hole, white-hole and no horizon. The spectra are dominated by a negative-frequency mode, which is the partner in any Hawking-type emission. An experiment in which an incoming positive-frequency wave is populated with photons is assembled to observe the transfer of energy to outgoing waves of positive and negative frequency at the horizon. The effect of mode conversion at the interface is clearly shown to be a feature of horizon physics. This is a classical version of the quantum experiment that aims at validating the mechanism of Hawking radiation.

To better manage deteriorating infrastructure, quantitative data about the performance of infrastructure assets is required. Rayleigh based distributed fibre optic strain sensing (FOS) is a technology that has the potential to offer this type of data and unlike traditional strain sensors it can measure the strain along the full length of the structure. A series of experiments were undertaken to develop installation techniques and evaluate sensor accuracy for typical civil engineering materials: steel, concrete and reinforced concrete. The results of these experiments showed that the choice of sensing fibre and adhesive was dependent on the material being monitored. When the sensing fibre and adhesive are chosen correctly, the Rayleigh system can provide the same accuracy as a strain gauge for steel and concrete, and useful measurements can be obtained even in areas of concrete cracking. The FOS technique was utilized to determine whether distributed strain measurements could be used to detect and quantify localized deterioration of the steel reinforcement (localized area reductions of 0-30%) at service loads. A series of specimens was tested, the sensing system was able to detect the presence of localized deterioration with embedded nylon and polyimide fibres, but the nylon fibre cannot quantify large strain gradients due to slip within the sensing fibre. The strain profiles gave insights to the failure mechanism occurring in the reinforced concrete specimens. The strain profiles for both test series indicated that the tension reinforcement was acting as a tension tie and the strain profiles suggested the presence of compressive struts indicative of an arching mechanism in the specimens. The Black River bridge in Madoc, Ontario was instrumented with fibre optics sensors to determine whether the use of FOS is both practical and beneficial for reinforced concrete bridge assessment when compared to conventional instrumentation. The FOS showed reasonably good agreement with conventional sensors. The fibre optic strain results are used to calculate curvature, slope and displacement but careful consideration of the boundary conditions is required. The results from the fibre optic sensors can be used to show the bridge load distribution and give insights into the support conditions of the beams. / Thesis (Master, Civil Engineering) -- Queen's University, 2013-08-21 11:56:53.276

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.