Investigation of the dynamic demodulation ability of a tilted fiber Bragg grating filter in an all-fiber displacement sensing system

Abstract

This paper investigates the dynamic detecting ability of a tilted fiber Bragg grating (TFBG)-based intensity modulation technique in an all-fiber displacement sensing system. The bandwidth of the spectrum of the TFBG is controlled via the fabrication process to obtain larger dynamic detecting range and high sensitivity. We demonstrate the dynamic demodulation ability of the TFBG by measuring the transient wave propagation on a square aluminum solid with an out-of-plane point-wise fiber Bragg grating (FBG) displacement sensor. The measurement sensitivity and the sensing range of the TFBG filter-based demodulation technique is compared with that based on an FBG filter. The accuracy of measurement for transient responses of particle motions measured by the FBG displacement sensor is verified by a laser Doppler vibrometer (LDV) simultaneously. The proposed TFBG filter-based displacement sensing system is proved to be able to measure transient point-wise displacement responses with high sensitivities. Unlike other traditional fiber grating filters, the desired demodulation range and sensitivity for the TFBG filter can be controlled via the fabrication process.