Fig. 1. New FBG vibration sensor. (a) I-typed section; (b) structure diagram; (c) physical drawing

Fig. 2. Modal simulation of the sensor. (a) Displacement nephogram of the first order modal; (b) strain nephogram of the first order modal

Fig. 3. Strain distribution. (a) Strain distribution of black curve position with length of 20.0 mm; (b) strain distribution at the grating paste position

Fig. 4. Sensor performance simulation. (a) Frequency response at acceleration of 2.0g; (b) accelerated response at vibration frequency of 300 Hz

Fig. 5. Testing system of the sensor

Fig. 6. Time-frequency response curves of the senor. (a) Time domain at 90 Hz; (b) frequency domain at 90 Hz; (c) time domain at 350 Hz; (d) frequency domain at 350 Hz

Fig. 7. Amplitude frequency response curve of sensor

Fig. 8. Spectra of short grating at different frequencies. (a) 90 Hz; (b) 350 Hz

Fig. 9. Acceleration response repeatability curve

Fig. 10. Anti-interference characteristic curve

Fig. 11. Structural damage simulation of I-beam

Fig. 12. Schematic of I-beam working condition

Fig. 13. Time-frequency domain response characteristic of the senor. (a)Time domain response of health status; (b) frequency domain response of health status; (c) time domain response of one crack; (d) frequency domain response of one crack ; (e) time domain response of two cracks; (f) frequency domain response of two cracks

Fig. 14. Energy ratio of three operating frequency bands. (a) Health status; (b) one crack; (c) two cracks

Fig. 15. Wavelet packet energy ratio characteristic

Fig. 16. Identification and comparison results between ELM and BP