Analysis of the phase response of fiber Bragg gratings to longitudinal ultrasonic fiields in the high frequency regime: towards new interrogation strategies

In this work the behaviour of a fiber Bragg grating (FBGs) phase response subjected to longitudinal ultrasonic (US) field has been investigated. Numerical results reveal high sensitivity of the FBG phase response and thus of the time delay to US waves in the high frequency and low amplitude regime. The potentialities to extend the sensing capability of FBG sensors as high frequency ultrasonic detectors are discussed with regard to new interrogation strategies based on time delay measurements.