Ultrasonic Active Fiber Sensor based on Pulse-echo Method

In this study, the concept of the ultrasonic active fiber sensor (UAFS) system based on the pulse-echo method was newly proposed for several mechanical and environmental sensors. A piezoelectric transducer, which was attached onto the end of the optical fiber, can be used for the ultrasonic wave generator and receiver. The piezoelectric patch was excited at its resonance frequency in the direction of length to generate the longitudinal ultrasonic wave, and was used for sensing the reflected signal on the end of the optical fiber. The emitted ultrasonic wave was propagated along the optical fiber and then reflected by a mechanical stimulus on the way. The time interval of the reflected ultrasonic wave was used to predict the location of the stimulus from the piezoelectric transducer. The UAFS was applied to monitor the cure conditions and to measure liquid level. In terms of the attenuation of the ultrasonic wave by the damping properties and the degree of coupling between the surrounding medium, the cure condition of the solder was successfully monitored and the water level was measured based on the linear relationship between liquid height and output signal.