Acoustic signal sensing using peak extraction and interferometric interrogation for <i>π</i> FBG sensor

Abstract A new peak extraction technique is proposed to isolate the central narrow peak of a π phase-shifted fiber Bragg grating ( π FBG) sensor, enabling acoustic signal detection through interferometric interrogation scheme. Owing to the complex spectral response of a π FBG sensor, direct measurement of sound signal using this sensor and interferometric demodulation approach is not feasible. To circumvent this, a pair of closely matched FBGs (OF1 &amp; OF2) is employed for central peak extraction, thereby discarding the undesired sections of the π FBG spectrum. The developed FlexiStretch concept is also tested for tunability and stability characteristics which is essential for any sensing system. The system design offers fine-tuned extraction of the central peak for π FBG over a tuning range of 220 pm and long-term stability for a period of 08 h. The system also has the inherent capability to manually adjust the spectral position of the two optical filters in order to negate any major spectral shift of the π FBG sensor position due to undesired environmental perturbations.