Fig. 1. Schematic of HiFi-DAS system

Fig. 2. Front and side views of pipeline and optical cable. (a) Front view; (b) side view

Fig. 3. Amplitude of leakage signal at each location

Fig. 4. 2560 differential phase traces demodulated under 0.2 MPa gas pressure

Fig. 5. Standard deviation curves at the end of fiber under different conditions. (a) No leakage; (b) 0.2 MPa gas pressure

Fig. 6. Standard deviation curves of leaking holes at different positions. (a) Position 1; (b) position 2; (c) position 3

Fig. 7. 2560 differential phase traces demodulated under 0.05 MPa gas pressure

Fig. 8. Noise statistics. (a) Power spectrum; (b) amplitude distribution

Fig. 9. Differential phase trace and standard deviation curve at the end of fiber after wavelet denoising under gas pressure of 0.05 MPa. (a) Differential phase trace; (b) standard deviation at the end of fiber