No-Core Fiber Based Multipoint Ultrasonic Acoustic Sensors for Energy Infrastructure Monitoring

This work investigates the potential of using simple inline no-core fiber (NCF)-based multipoint acoustic sensors providing high frequency bandwidth and dynamic range for ultrasonic guided waves and acoustic emission monitoring, thus offering an effective alternative to conventional piezoelectric (PZT) sensors for diverse non-destructive evaluations and structural health monitoring applications. A multipoint fiber optic acoustic sensor system based on thin NCF has been developed and its performance is extensively examined. The NCF sensor can accurately monitor acoustic events in an ultrasonic frequency range of ∼600 kHz with a maximum signal-to-noise ratio of over 50 dB. To demonstrate practical applications, the multipoint fiber acoustic sensor system was evaluated in pipeline monitoring for detection of multiple defects using active guided waves (GWs) excitation-based acousto-ultrasonic (AU) method, followed by an evaluation of the electrical transformer for detection of passive acoustic emission (AE) signals in response to partial discharge emissions. In both health condition monitoring applications, a very good agreement has been found between the acoustic responses of the ultrasonic fiber-optic acoustic sensors and that of the electrical sensors. The work presented validates the multipoint fiber-optic acoustic sensor system utilization for detection of weak acousto-ultrasonic GWs and AE signals, showing their potential for practical condition monitoring applications, especially in the area of energy infrastructure monitoring.