By "intelligently" locating a sensor with respect to its environment it is possible to minimize the number of sensing operations required to perform many tasks. This is particularly important for sensing media which provide only "sparse" data, such as tactile sensors and sonar. In this thesis, a system is described which uses the principles of statistical decision theory to determine the optimal sensing locations to perform recognition and localization operations. The system uses a Bayesian approach to utilize any prior object information (including object models or previously-acquired sensory data) in choosing the sensing locations.

D.Ing. (Electrical and Electronic Engineering) / The subject of this research work was the reflective fibre optic ring interferometer utilizing allow coherence length source. The interferometer consists of an interrogating fibre connected to a fibre ring via an input/output splitting coupler, and a reflector. The fibre ring is formed between one input and one output leg of a fibre coupler. The reflector can be of any type, including a fibre loop mirror, Faraday rotator mirror, a silvered fibre end-face or multilayer dielectric mirror deposited on the fibre end face. A theoretical treatment was developed for the interferometer. It was shown that the interferometer had a reflectance vs nonreciprocal phase shift characteristic, similar to that of a Fabry-Perot interferometer. Upon phase modulation of the interferometer quadrature terms were obtained at harmonics of the modulation frequency. It was shown that by decreasing the finesse of the sensor a quadrature phase tracker could be employed. The dependence of the sensor's reflectance, finesse and sensitivity on various system parameters were simulated with the aid of the abovementioned theory. A high finesse interferometer was proposed. It utilizes a fibre doped amplifier which would increase the sensitivity above that of a Sagnac interferometer. Intermediate and low finesse versions of the reflective ring interferometer were applied as gyroscopes...

L’utilisation de capteurs à fibres optiques pour le génie civil n’est pas une idée nouvelle. Leur intérêt repose principalement sur les propriétés intrinsèques des fibres optiques: neutralité électromagnétique, capacité de multiplexage importante et accès à de longues distances de mesure. Ces capteurs sont susceptibles de couvrir de nombreuses fonctions des capteurs traditionnels : détection, localisation et surveillance. Grâce à des interactions entre la lumière et la fibre optique, telle que la diffusion Brillouin, la fibre optique peut constituer, sur toute sa longueur, un capteur continûment distribué. Le phénomène de diffusion Brillouin est très étudié de part sa grande efficacité de diffusion, sa dépendance vis-à-vis de la température et de la déformation et sa portée pluri-kilométrique. Cependant, la sensibilité de la fréquence de décalage Brillouin à la fois à la température et à la déformation rend problématique la mesure simultanée de ces deux paramètres. Nous présenterons une possibilité de discrimination de la température et de la déformation correspondant aux précisions souhaitées en terme de surveillance d'ouvrage de génie civil. / Optical fibers sensors for civil engineering are not a new idea. Their interest is based mainly on the intrinsic properties of optical fibers: electromagnetic neutrality, important capacity of multiplexing and access to long distances of measure. These sensors may cover numerous functions of the traditional sensors: detection, localization and surveillance. Thanks to interactions between the light and the optical fiber, such Brillouin scattering, the optical fiber can be on all its length, a continuously distributed sensor.The phenomenon of Brillouin scattering is well studied due to its big efficiency of scattering, its dependence towards temperature and strain and its pluri-kilometric reach. However, the double sensibility of the Brillouin frequency in temperature and strain is problematic for the simultaneous measurement of these two parameters. We shall present a possibility of discrimination of temperature and strain corresponding to the precisions wished for surveillance health monitoring.

An index grating is a periodic perturbation of the refractive index in a waveguide's axial direction. Gratings have important roles in optical communication as spectral filters and dispersion compensators. The spectral response characteristics of gratings can be controlled by shaping the profile of the index modulation, a process called apodization. Apodizing different layers of the grating using different apodizing functions is proposed for adding more degrees of freedom to the design. An approach to designing a two-layer separately apodized grating that yields virtually the same reflectivity and dispersion responses as an arbitrary zero-"dc", apodized, un-chirped grating is proposed. A design example is presented, and coupled-mode theory is employed to compute the reflectivity responses of the original zero-"dc" design and the nearly equivalent separately-apodized design proposed in this thesis. An approach to designing a four-layer separately apodized grating that yields virtually the same reflectivity and dispersion responses as an arbitrary chirped grating is proposed. The largest bandwidth a four-layer separately-apodized grating designed using this approach can yield is as large as the largest bandwidth a variable-period conventional design can yield. Also, a similar, less-capable design approach is proposed for two-layer separately apodized gratings that are equivalent to conventional, chirped gratings. Design examples are presented. For all of the separately apodized gratings designed, the layers have a varying "dc" index change that is proportional to the varying "ac" index change. Furthermore, the period, which is the same in every layer, is constant, i.e. independent of the position. Both considerations enhance the prospects of fabricating the separately-apodized designs using a simple, reproducible technique. One such technique is proposed that separately-apodizes halves of the waveguide, instead of layers, but the design approaches are easily adjusted to this case. / Master of Science

A model is developed for the optimization. The model can be used for the merger of both identical and non-identical networks. The overall costs for various topologies are optimized with respect to different interconnection build costs. It is shown that the merger of two optical networks can reduce more than 50% of operational fiber links, while routing between any two nodes in the two optical networks are maintained. This has been proven through case analysis and analytical results. / An algorithm for resource optimization is also developed for the consolidation of two coexisting networks. In all cases after critical interconnection build cost, only two interconnection fiber links are needed. It is shown that the optimization is to find a Hamiltonian path that covers all the nodes in each network or to find a path that contains a maximum number of directly connected articulation nodes with different groupings. / Case analysis results for part of a real China network and other topologies are discussed. Analytical results can be derived for both the minimum number of links required for arbitrary connected networks and the locations of the two interconnections for the merger of two networks. In addition, more comprehensive analysis on the effects of node degree, protection, and traffic demand are discussed. It is conclusive that through the merger of two optical networks substantial saving to the network operator will occur. / In this thesis, the merger of two networks by adding interconnection fiber links is investigated. Interconnection fiber links are only allowed at the co-located nodes of the two networks. With the additional interconnection links, it is possible to reduce the number of fiber links that are operational while maintaining the full connectivity between any two nodes in the two networks. By suspending some of the fiber links, the operational expenses of those links can be saved. Optimal cost and the number of interconnection links with their optimal locations for the merger of the two optical networks are investigated. / Telecommunication networks have been designed to carry voice traffic for decades. With the growth of data traffic in recent years, network operators have constructed substantial amount of fiber optic networks. Multiple telecommunication networks create redundancy in fiber resources. Resources have not been used optimally and revenue has plunged to its lowest since inception. Many network operators are considering co-location and merging in order to reduce cost. Merging two networks can achieve operational savings in redundant fiber links and therefore cost saving to the network operator. / The proposed model finds the optimal interconnection locations for different topologies. We analyzed the optimal location for several cases when the number of interconnection fiber links is two and some analytical results are derived. This assists network planners to focus on the optimal locations for interconnection links to be installed. / Leung, Raymond Hai Ming. / Adviser: Lian Kuan Chen. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3690. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 112-115). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

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A theoretical study of an electrically passive, loss-compensated, optical position sensor is the goal of this project. Optical fiber sensors exploit light as the information carrier. Fiber-optic sensors consist of a constant light source launched into an optical fiber and transmitted to another point at which a measurement is made.In the proposed optical position sensor, a Light Emitting Diode (LED) produces a constant beam of light, which is channeled through an optical fiber to a Graded Index (GRIN) lens. This lens makes all the light rays parallel to one another, a process called collimation. The light then enters a polarizer which is a lens that further orders the light rays in a process called polarization.Then the light enters a chamber in which a doubly refracting (birefringent) crystal is situated. The crystal is a wedge, and thus has a varying thickness throughout its length. The light beam strikes the crystal, sending a spectrum, or spectral signature, that is distinct to the particular thickness of the crystal. That signature goes directly from the chamber housing the crystal into a lens called an analyzer which orders the light again through polarization. Then the light goes into another GRIN lens, and this GRIN lens focuses the light onto an optical fiber, which transmits the particular spectral signature of this light to an optical spectrum analyzer (OSA). The OSA uses a Photodiode Array to accept the incoming light, a device that takes in light and redistributes it to a monitor for display by the user. Such a device is called a detector. The thickness of the crystal that the light travels through is determined by the crystal's position.If the crystal rests on a platform which is connected to an object whose position must always be monitored, then the crystal will move as the object moves. The different spectral signatures shown on a monitor reveal different thicknesses of the crystal, which reveal different positions of the monitored object. The object whose position is measured is the measurand.The selected crystal is quartz. It has a 12.5-mm length, a width of 10.8-mm at its thinnest end, and a taper angle to the thickest end of only 0.008 degrees, which corresponds to a 0.17-micron difference between the two. This angle is called the polishing angle of the quartz. The quartz itself is called the active cell. The Photodiode Array Detector receives the spectral signature from the optical fiber, and that signature is projected on an OSA, which is software built-in to the computer. A mathematical program is used to evaluate the signature, and the position of the measurand is thereby revealed. How accurate the measurement is can be revealed by use of a control device. If the quartz crystal is moved by a measuring device, such as a micrometer, the distance that the crystal moved may be measured by the micrometer, as well as by the OSA. By comparing the two, the accuracy of the spectrograph, and the position it reveals, can be known. / Department of Physics and Astronomy

At present, optical fiber transmissions are dominated by intensity modulation and direct detection, which fundamentally limit the signal processing capabilities in optical fiber networks. On the other hand, manipulation of optical phase enables advanced signal processing techniques for various applications. This thesis includes three parts and makes contributions in three research areas in optical fiber networks, by applying optical and electronic signal processing techniques. In the first part of the thesis, optical signal processing is employed to realize a novel all-optical label swapping (AOLS) technique using synchronous phase modulation. This technique is shown to address the forwarding speed bottleneck in optical packet switched networks (OPSN). By exploiting the unique symmetry of phase-shift keying (PSK), for the first time, label erasure and insertion are performed in a single step by a phase modulator without wavelength conversion. We also propose and demonstrate a polarization insensitive phase modulator to address the polarization sensitivity of AOLS. Furthermore, we emulate multi-hop all-optical label swapping in a re-circulating loop to investigate the power penalties from the accumulated phase errors and the timing mismatch. Based on the experimental and analytical results, we show that this technique can save wavelength converters significantly if compared with conventional AOLS techniques requiring dedicate wavelength converters.

Thesis (Ph.D.)--Pennsylvania State University, 2007. / Mode of access: World Wide Web.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 77-79). Also available via the Internet.