| Summary: | 碩士 === 國立成功大學 === 機械工程學系碩博士班 === 95 === As for the application on optical fiber sensor, we combine the advantages of traditional LPG sensor and present prism coupler surface plasmon resonance (SPR) sensor. Now we further propose a novel type of optical fiber SPR sensor. It simply employs a long-period fiber grating with proper period to couple a core mode to the co-propagating cladding mode that can excite surface plasmon wave (SPW) and monitors the change of the transmitted core mode power, which is operating at a fixed wavelength, to determine the variation of the refractive index of analyte.
As far as the excitation of SPW, the model of numerical simulation, and the complexity of measurement equipment are concerned. In this dissertation, we derive the dispersion relation of guiding modes in this four-layer optical-fiber SPR sensor, and the unconjugated form of coupled-mode equations. In order to increase greatly the efficiency on analyzing this new SPR sensor, further simplifications on the integration form of coupling constants are proposed. In addition, we also do some basic experiment to confirm its application.
In order to understanding more about our specific period, we also discuss about the relationship between mode order and period of LPG by simulating. We calculate from two aspects which are period fixed and cladding mode order fixed to inspect the affect between each other. From the results of simulation, we can plot diagrams of the cladding mode order against grating period and effective refractive index in cladding mode against the period of grating for resonant wavelength at 1550 nm. In aspects of mathematics and physics, all cladding modes exist possibly by solving the structure of fiber through arithmetic equations. But to be concerned with practicality, it is impossible to control the cladding modes independently and accurately.
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