Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 305 for “"gratings"”.
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Acoustic Scattering by Gratings
… is compared against techniques for infinite gratings, such as the Wiener--Hopf technique. It is found that the novel method shows much greater flexibility around the lengths of the apertures; furthermore, the evaluation of the scattered field is easier and faster. This work further extends to …
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Microscopic characterisation of fibre Bragg gratings
… of optical fibres and fibre Bragg gratings, by the use of a non-invasive microscopic technique, namely differential interference contrast microscopy. The thesis aims to provide detailed information on the structural and optical properties of optical fibres and fibre Bragg gratings. …
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Advanced fibre gratings and their applications
… study of many distinguishing structures of fibre gratings. Starting from the Maxwell equations, the coupled-mode equations for both FBG and LPG were derived and the mode-overlap factor was analytically discussed. Computing simulation programmes utilising matrix transform method based on the models …
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Gratings With Multiple, Independently Apodized Layers
… 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. …
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Integrated chirped Bragg gratings for dispersion control
In this work, the need for an integrated optical dispersive device is discussed, with particular reference to pulse compression of semiconductor mode-locked laser (MLL) pulses that exhibit temporal chirp and therefore, worse than transform limited behaviour. It is shown that current techniques in …
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Fabrication and applications of fibre Bragg gratings
The consequences of fabricating Bragg gratings in various fibres, with or without hydrogen loading, and with varying laser power levels are explored. Three new techniques for fabricating chirped gratings are presented. Beams with dissimilar wavefront curvatures are interfered to give chirped …
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Fabrication of extremely smooth blazed diffraction gratings
High efficiency diffraction gratings are important in a variety of applications, such as optical telecommunications, lithography, and spectroscopy. Special interest has been placed on blazed diffraction gratings for their ability to enhance diffraction intensity at the specular reflection angle off …
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Surface acoustic wave gratings of finite width
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1979.
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Long-Period Gratings as Immuno-Diagnostic biosensors
This research presents a novel biosensor which utilizes the refractive index sensitivity of a fiber optic long-period grating. The long period grating couples light from the forward propagating guided core mode of a single-mode fiber into discrete circularly symmetric cladding modes. Due to …
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Intragrating sensing using chirped optical fibre Bragg gratings
… sensing systems employing chirped fibre Bragg gratings (CFBGs) are investigated. Intragrating sensing is the process of obtaining a continuous profile of a measurand over the grating length from either the amplitude or phase, or both the amplitude and phase of its measured reflection response. …
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Passive and active Bragg gratings for optical networks
… phase en/decoders and the tunable fibre Bragg gratings based on an S-bending technique. The advantage of an S-bending tuning FBG is that its central wavelength is invariant as the linear strain gradient along the FBG is altered. Two new devices are developed by embedding a pair of FBGs in a …
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Fibre bragg gratings for microwave photonics and sensing
… Some theoretical background about fibre Bragg gratings, photosensitivity, fibre Bragg grating sensors and filters are presented. Fibre Bragg grating sensors in other industrial applications are highlighted. Some sensing principles are also introduced. Experimental work is carried out to …
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Experimental and theoretical characterisation of tunable fibre gratings
… and experimental aspects of UV written fibre gratings. The main body of the thesis deals with the design, fabrication and testing of telecommunication optical fibre grating devices, but also an accurate theoretical analysis of intra-core fibre gratings is presented. Since more than a decade, …
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Fiber Bragg Gratings Strain Sensors for Railway Applications
Fiber optical sensors have played an important role in applications for monitoring the health of civil infrastructures, such as bridges, oil rigs, and railroads. Due to the reduction in cost of fiber-optic components and systems, fiber optical sensors have been studied extensively for their higher …
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Integrated optical filters using Bragg gratings and resonators
… of optical filters made using integrated Bragg gratings and Bragg resonators. Various topologies for making add/drop filters using integrated gratings are outlined. Each class of devices is studied in detail and the theoretical tools needed for designing the add/drop are developed. First-order …
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Properties and sensing applications of long-period gratings
… the spectral modulation provided by long-period gratings. An analytical model is developed to predict the location of the resonance bands as functions of the grating period and the parameters of the host fiber. These gratings with small insertion loss and negligible back-ret1ection are shown to …
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Microscopic and spectral characterisation of optical Fibre Bragg gratings
Fibre Bragg gratings (FBGs) have found extensive application in lasers, amplifiers, signal filtering in telecommunications and sensing. The underlying mechanisms and fundamental properties of FBGs are not completely understood, which stands in the way of full exploitation of FBG-based devices …
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