Fibre Bragg Grating-Based Cascaded Acoustic Sensors for Potential Marine Structural Condition Monitoring

This paper explores the potential of using multiple fibre Bragg grating-based sensors for acoustic emission (AE) detection, thus offering an effective alternative to conventional piezoelectric (PZT) sensors, especially where they have shown limitations in use, such as in the marine sector. A cascaded fibre optic acoustic sensor system, using optical filter signal demodulation has been developed and its performance extensively evaluated. To undertake this under standardized conditions, the optical sensor system was evaluated using a glass plate to detect the acoustic signal, followed by an evaluation using a metal plate to identify the location of acoustic sources, when subjected to sonotrode excitation, mimicking acoustic detection in cavitation detection. Under these circumstances, very good agreement has been reached between the outputs of the optical acoustic sensors and of the colocated PZT acoustic sensors. This work confirms the utility of these sensors-they can detect not only weak AE signals, but also enable multipoint simultaneous measurement, showing their potential for condition monitoring applications, especially in the marine sector.