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.