Browsing by Author "Vengsarkar, Ashish Madhukar"

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    Localized wave solutions in optical fiber wavelengths
    Vengsarkar, Ashish Madhukar (Virginia Tech, 1991)
    A novel bidirectional decomposition of exact solutions to the scalar wave equation has been shown to form a natural basis for synthesizing localized wave (LW) solutions that describe localized, slowly decaying transmission of energy in free space. In this work, we demonstrate the existence of LW solutions in optical fiber waveguides operated in the linear regime. In this sense, these solutions are fundamentally different from the non-linear, soliton-based communication systems. Despite the dielectric waveguiding constraints introduced by the fiber, solutions that resemble the free-space solutions can be obtained with broad bandwidth source spectra. As with the free-space case, these optical waveguide LW solutions propagate over very long distances, undergoing only local variations. Four different source modulation spectra that give rise to solutions similar to Focus Wave Modes (FWM’s), splash pulses, the scalar equivalent of Hillion’s spinor modes and the Modified Power Spectrum (MPS) pulses are considered. A detailed study of the MPS pulse is performed, practical issues regarding source spectra are addressed, and distances over which such LW solutions maintain their non-decaying nature are quantified. Present day state-of-the-art technology is not capable of meeting requirements that will make practical implementation of LW solution-based fiber optic systems a reality. We address futuristic technology issues and briefly describe efforts that could lead to efficient LW solution-based fiber optic systems.
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    Novel microbend loss fiber optic hydrophones for direction sensing
    Vengsarkar, Ashish Madhukar (Virginia Tech, 1988-08-05)
    Dual purpose fiber optic microbend loss sensors have been developed for measurement of underwater acoustic wave amplitudes and for detection of the direction of wave propagation. Cylindrical sensing elements with external threads have fibers wound around them. Axial slots, cut along the length of the cylinder and deeper than the threads, provide the microbends. Three different construction schemes for cylindrical sensing elements are built. The dual purpose hydrophones are characterized for frequencies ranging from 15 kHz to 75 kHz. Based on the results, an improved design that uses the wavelength dependence of microbend loss in a single mode fiber is proposed.