Frequency response of fiber optic ultrasound sensors

In this work the response of an embedded fiber optic ultrasound sensor has been investigated. Calculations were performed which 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 frequency and incident angle. Experiments were performed to validate the calculations. Induced phase shifts were measured for the case of normally incident ultrasound impinging upon a submerged and an embedded fiber sensor. The case of obliquely incident ultrasound was also investigated for an embedded fiber at angles up to 4 degrees. The experimental measurements were performed over a bandwidth from 2 MHz to 8 MHz.