Ultrasensitive Optical-fiber Ultrasonic Sensor Based on Phase-shifted Fiber Bragg Gratings

Using optical method in structural health monitoring (SHM) is getting more and more attentions recently due to the inherent advantages in fiber optical method. In this research, we proposed an ultrasonic phase-shifted fiber Bragg grating (PS-FBG) sensor and demonstrated its application to ultrasonic SHM. Based on this sensor, two different demodulation systems were developed, named as cascaded PS-FBG sensing system and PS-FBG balanced sensing system, for acousto-ultrasonic detection and acoustic emission detection. The experimental results show that PS-FBG sensor with higher sensitivity compared to other existent FBG has a potential to replace traditional ultrasonic lead-zirconate-titanate sensors.