Output response characteristics of resonant-type guided-wave optical acoustic emission sensor

Our group has proposed a resonant-type guided-wave optical acoustic emission (AE) sensor, which consists of a diaphragm and a single-mode optical waveguide on the diaphragm. In this study, we examined output response characteristics of the AE sensor using an acoustic sound pulse, instead of an AE pulse. Output responses of a fabricated AE sensor were investigated for each parameter, namely pulse duration, sound pressure (amplitude) and frequency. A larger output signal was obtained due to resonance effect, but it lacked similarity to the original target pulse due to a narrow bandwidth and required approximately 10 ms to reach the steady state. However, based on the experimental results, a formula was derived to determine pulse duration and amplitude. In the case of out-of-resonance, output signal is more complex, but the frequency deviation from the resonance frequency could be determined from the beat-like phenomenon for long-duration pulse.