Master of Science / Department of Civil Engineering / Asadollah Esmaeily / Engineers involved in construction face various challenges. One of them being dealing with cracks in concrete. Naturally, concrete is weak in tension defining its bristle characteristics. To compensate, fiber reinforcement is used in the concrete mixes. Popular fiber types are steel, glass, polypropylene, and carbon fibers. These types of fibers are used to reinforce concrete. These fibers all increase the tensile and flexural strength of concrete. Additionally, they all have their own advantages. This paper is oriented to briefly introduce basic properties of these fibers. This includes the composition, production, advantages, applications, and restrictions of the mentioned fibers.

M.Ing. / This thesis covers the theory and development of fused, biconically tapered, fibre-optic couplers and their application in sensors. The optical coupling between fibres is described by means of the coupled-mode theory in the case of a weakly guiding coupler. Firstly, simplified expressions for the guided modes in an optical fibre are derived. This is followed by the derivation of the coupled-mode equations for a perturbed waveguide. The coupled-mode equations are then used, together with the expressions for the guided modes, to determine the coupling coefficient for a weakly guiding coupler. In the case where the coupler is not weakly guiding, a model based on a rectangular dielectric waveguide is presented. A process for the manufacture of fibre-optic couplers, based on the fusion and elongation technique, was developed. This process is described and special attention is paid to the influence which different process parameters has on the properties of the couplers. During the development, the coupling theory was utilized to optimize the process. Results obtained with couplers manufactured by this process, are presented. A specific application of couplers, namely a new type of fibre-optic coupler sensor, was developed. The operation of the sensor relies on the change of the coupling ratio with an axially applied mechanical strain. Analog signal processing of the two outputs yields a signal which is directly proportional to the strain and which is independent of fluctuations of the light source power. The sensor was investigated experimentally by manufacturing temperature and elongation sensors which work on this principle. The operation and features of these sensors are presented, together with very promising experimental results.

Light loss in single mode fiber optical switches is investigated. Loss due to reflection, aberration and fiber misalignment are evaluated. A simple model of image to fiber end face overlap for the fiber/lens system is developed. The intensity distribution of light in the fiber and imaging system is assumed to be gaussian. It was found that aberration is a major cause of loss and that fiber misalignment did not cause as much loss as expected. Loss due to reflection is assumed to be minimal due to the presence of anti-reflection coatings on the optical components. / Master of Science

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An analysis of modal noise in multimode optical fibers was performed. Both spatial and time varying modal noises were analyzed. The time varying modal noise was g.enerated in two ways: the first, by vibrating the optical fiber, the second, by varying the temperature of the optical fiber. Under controlled conditions the temperature of the optical fiber varied between 68°F to 200°F while the fiber was held stationary. The optical fiber was then vibrated while the temperature was held constant. Data indicated that the modal noise statistics agreed with the Beta distribution. The statistics of the spatial modal noise were measured and were then compared to the time varying modal noise. These statistical moments disagreed with the Beta statistics. This indicated that modal noise generated in optical fibers is possibly a non-ergodic process. Next the optical fiber's spatial auto-correlation function and spatial intensity fade statistics were computed.

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.

The fiber grating external cavity laser (FGECL) module packaged with fiber bragg grating and FP laser diode is investigated. The optical spectrum of FGECL is single longitudinal mode. In order to get stable single longitudinal mode, the FP laser diode coated with an AR-coating (reflectivity is 0.5%). To achieve higher coupling efficiency between laser diode and fiber, the hyperbolic-end lensed fiber is used. A coupling efficiency of up to 86% has been demonstrated. The alignment and fix between laser diode and fiber are accomplished by laser welding technology. The results of FGECL module show that the output power and side-mode suppression ratio (SMSR) are more than 2mW and 44dB, respectively. Comparing to the non-AR coated FGECL, the result of SMSR is 5 dB improved. Dynamic tests of the FGECL module operate at 2.5Gbps, including the eye diagram, bit error rates, impedance matching of laser diode, signal current, and the limit of the dispersion in the optical communication system has been measured. The FGECL module can meet the ITU-T G.957 standard.

Here choose wedge-shaped fiber, which have sample shape, low manufacture cost and time, to manufacture wedge-shaped fiber array in the paper. In order to reduce cost, it depends on change and reduce manufacture process steps.

Thesis (doctoral)--Lund University, 1997. / Added t.p. with thesis statement inserted.