Optimized acoustic wave detector based on long period grating

Abstract

In this paper, a long period grating (LPG)-based optical fibre sensor system designed for narrow band acoustic wave detection is presented and a means to optimize it is investigated. Due to the fibre being fixed at both extremities, a string resonance appears allowing a narrow band sensitive detection of sound. Varying the curvature of the LPG creates a change in the shape of frequency response of the sensor. By selecting carefully the curvature of the fibre, a ten-fold increase in the detected signal intensity is demonstrated thereby making the sensor a suitable candidate for sound detection in harsh environments taking advantage of the properties of the optical fibres involved.