Fig. 1. OFDR monitoring principle

Fig. 2. DAS monitoring principle

Fig. 3. Schematic diagram of indoor test equipment

Fig. 4. Pipeline damaged strain monitoring. (a) Schematic diagram of event A₁ device; (b) schematic diagram of strain monitoring for event A₂; (c) indoor test picture

Fig. 5. Temperature monitoring model diagram. (a) Diagram of event A₁ device; (b) event A₃ empty pipe status; (c) event A₃ 1/3 water status; (d) event A₃ full water status; (e) indoor test picture

Fig. 6. Vibration monitoring model diagram. (a) Device diagram; (b) indoor test picture; (c) vibration cable layout diagram

Fig. 7. Strain monitoring result curves. (a) Monitoring results of centralized drop strain; (b) monitoring results of fine sand drop strain

Fig. 8. Temperature monitoring result curves. (a) Temperature curves of empty pipe corrosion zone; (b) temperature curves of 1/3 water corrosion zone in pipe; (c) temperature curves of full water corrosion zone in pipe

Fig. 9. Linear fitting diagrams of temperature time domain curve. (a) Empty pipe status; (b) 1/3 water in pipe; (c) full water in pipe

Fig. 10. Calibration signal of damaged area of pipeline. (a) Calibration in the front of damaged area; (b) calibration at the end of damaged area

Fig. 11. Original signal diagram

Fig. 12. Short-time Fourier transform time-frequency diagram

Fig. 13. Original signal diagram of 0.2‒0.6 s

Fig. 14. Kurtosis value diagram

Fig. 15. Absolute mean amplitude curve

Fig. 16. FFT frequency domain curve

Fig. 17. Frequency peak shift diagram

Fig. 18. Data fusion result curves. (a) Strain-temperature-absolute average amplitude; (b) strain-temperature-peak frequency

Fig. 19. Strain-temperature-vibration collaborative application model