Response of an embedded fiber optic ultrasound sensor

Abstract

In this work the response of an embedded fiber optic Fabry–Perot ultrasound sensor has been investigated. Calculations were performed that model the fiber as a cylindrical elastic inclusion subjected to obliquely incident harmonic plane waves. The phase shift of the light traveling in the fiber was calculated along the principal strain axes as a function of ultrasonic frequency and incident angle. Experiments were performed to validate the calculations. Induced phase shifts were measured for the cases of normally incident ultrasound impinging upon a fiber sensor submerged in water as well as embedded in epoxy. The case of obliquely incident ultrasound at angles up to 4 deg was also investigated for a fiber embedded in epoxy. The experimental measurements were performed over a bandwidth from 2 to 8 MHz.