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In this paper, a geometrical acoustics method has been presented to describe acoustic wave propagation in a fiberacoustic waveguide in which the acoustic velocity varies continuously in the radial direction. Based on the acoustic wave equation, a WKBJ approximate method has been used to analyze the propagation and cutoff characteristics of guided acoustic modes in this waveguide. It is believed that this acoustic fiber can transmit acoustic and optical signals at the same time when the refractive index of the core material is greater than that of the cladding material and the acoustic velocity of the core material is less than that of the cladding material. Furthermore, this type of acoustic fiber is suitable because of low loss and hence long distance transmission paths.

This paper presents a discussion of multimode optical fibers used for acoustic wave (2–10 MHz) propagation. The optical fiber acts as a connecting rod between two piezoelectric transducers (PZT) that are attached at each end (dumbbell arrangement). This device is then completed by encapsulation of a solid epoxy or a strengthened composite. One piezoceramic is excited and generates an elastic wave to propagate along the optical fiber and into the other piezoceramic. An alteration of the steady‐state signal thus is indicative of an impact and/or random pressure disturbances upon the composite. Additionally, environmental temperature changes are also detectable. Experimental measurement and related theories are demonstrated.