Angular Dependence of the Frequency Response of an Extrinsic Fabry–PÉrot Interferometric (EFPI) Fiber Acoustic Sensor for Partial Discharge Detection

Extrinsic Fabry-Peacuterot interferometric (EFPI) fiber acoustic sensors have been successfully employed in partial discharge detection in a power transformer. In this paper, the angular dependence of the sensor's frequency response is investigated. The interaction between the applied pressure and the EFPI fiber sensor immersed in a fluid was modeled by finite element methods. The angular dependence of the sensor's frequency response was obtained by a coupled structure acoustic analysis in ANSYS and compared to both the soft baffle and unbaffled models and experimental results in a 1-m tank. The measured bandwidth of the sensor's angular dependence of the frequency response is in good agreement with the simulation results with a plusmn3deg 3-dB bandwidth difference and a 0.4-dB difference within a plusmn45deg incident range.