Study on phase shifted fiber Bragg grating spatial sensing properties to ultrasonic wave at arbitrary excitation angle

Taking into account the birefringence effect, the sensing models of phase shifted fiber Bragg grating (PS-FBG) under ultrasonic wave from arbitrary excitation angle were established, and its reflection spectrums were analyzed by simulation based on the transfer matrix principle. Under the excitation of transverse ultrasound, the PS-FBG sharp dip was split into two peaks due to birefringence, the split point spacing increased with the transverse force; under the effect of the ultrasonic wave from random angle, the PS-FBG signal intensity and the ultrasonic excitation angle presented a Cosine curve with two peaks in the middle. Finally, the relevant conclusions were verified by experiments and 12.11 MHz ultrasonic wave was obtained by PS-FBG.