Fig. 1. Detection diagram of laser ultrasound signal by Fizeau fiber interference

Fig. 2. Multi-channel fiber interference sensing system

Fig. 3. Multi-channel fiber probe

Fig. 4. Schematic diagram of multi-channel wave velocity measurement

Fig. 5. Elastic surface wave signals

Fig. 6. Signal spectra of defective and non-defective samples measured by single-channel interferometer

Fig. 7. Transmission path of elastic surface wave signal

Fig. 8. Elastic surface wave signals of non-defective sample measured by multi-channel interferometer

Fig. 9. Echo reflection path of circular hole defect

Fig. 10. Measured 18 channel signals

Fig. 11. Position of reflection point of defect echo