Modeling And Characterization Of A Fabry Perot Pressure Sensor
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Fabry-Perot interferometers (FPIs) have been used as sensing elements for pressure transducers in many applications. Most of the current FPI pressure sensors measure amplitude changes of the reflected signals from a deformable diaphragm. A new technique to design an FPI pressure sensor has been proposed in this thesis. The proposed methodology aims to maximize the sensitivity by measuring frequency shifts and optimize the dimensions of the sensors for various materials and applications. The sensor diaphragm is built directly on the end surface of an optical fiber with a sacrificial layer introducing the required FPI cavity height. The resulting sensor detects frequency shifts transduced by pressure variations deforming the diaphragm. The sensor is modeled on two theories and a methodology is derived combining an iterative analysis between the mechanical characteristics and the optical performance to achieve optimal sensitivity. Applying this methodology, design parameters for different applications are extracted. The practical issues of designing a fiber optic Fabry-Perot pressure sensor have been investigated. Structural modifications are introduced to optimize the dimensions without compromising sensitivity. A bossed diaphragm structure is proposed to eliminate the effects of optical scattering from the reflection surface. Different configurations of the bossed structures under conditions of diverse diaphragm supports have been studied. The optical performance and sensor dimension combination that yields in the maximum sensitivity has been achieved. The modeling-based methodology has been adopted to choose design parameters for different materials, catering to the requirements of small sensor dimensions over numerous different applications.