Polarimetric fiber‐optic ultrasonic sensor for the nondestructive evaluation of materials

A fiber‐optic polarimetric interferometer has been used as an ultrasonic sensor in a feasibility study of flaw detection and nondestructive evaluation of materials. The sensor is based on acoustic modulation of the birefringence of a polarization‐maintaining fiber. The small size of the fiber and the ability to embed it in materials provide significant advantages over conventional transducers. When the fiber and sample are both immersed in water, sample thickness and flaw location, size, and orientation have been evaluated. The fiber has also been embedded in a Plexiglas specimen and has shown the potential to locate internal flaws. [Work supported, in part, by NSF.]