Zhe Ma, Mingjiang Zhang, Junfeng Jiang, Jianzhong Zhang, Liantuan Xiao, Tiegen Liu. Fiber-Optic Distributed Acoustic Sensing Technology Based on Linear Frequency Modulation Pulses[J]. Laser & Optoelectronics Progress, 2023, 60(11): 1106002
- Laser & Optoelectronics Progress
- Vol. 60, Issue 11, 1106002 (2023)
Fig. 1. DAS technical classification based on modulated pulse frequency components. (a) Single frequency pulse φ-OTDR; (b) multifrequency pulse φ-OTDR; (c) LFM pulse φ-OTDR
Fig. 2. φ-OTDR discrete scattering element simplified model. (a) Without disturbance; (b) disturbance
Fig. 3. Discrete theoretical model of LFM pulse distributed acoustic sensing
Fig. 4. Typical structure of LFM pulse DAS system
Fig. 5. Discrete scattering model of LFM pulse in optical fiber
Fig. 6. Principle of step frequency scanning sensor. (a) Step frequency scanning; (b) data processing structure
Fig. 7. Frequency shift compensation principle of LFM pulse
Fig. 8. Sensing principle of wavelength scanning method. (a) Wavelength scanning; (b) data processing structure
Fig. 9. Basic principle of pulse compression[50]. (a) Matched filter; (b) unmatched filter
Fig. 10. Waterfall plot over a 40 s period for a section of field fiber[57]
Fig. 11. Waterfall plot for the full 209.4 km link produced by the real-time LFM-DAS[57]
Fig. 12. Optical pulse compression reflectometry. (a) Experimental setup; (b) spatial resolution of Gaussian pulse[39]
Fig. 13. LFM pulse combined with unmatched filtering technology. (a) Experimental setup; (b) strain distribution; (c) standard deviation of strain distribution[51]
Fig. 14. Interleaved identical LFM pulses technology[61]. (a) Experimental setup; (b) power spectral density
Fig. 15. Schematic diagram of LFM pulse principle of HDSB[66]. (a) Sensing fiber; (b) HDSB-LFM pulse; (c) coherent time-domain signal
Fig. 16. Comparison of measurement results between DAS and geophones[74]. (a) Measurement results of DAS; (b) measurement results of geophones; (c) comparison of detection waveforms
Fig. 17. Comparison of DAS and geophone[83]. (a) Measurement results of DAS; (b) VSP results of the Z-direction component of the detector
Fig. 18. DAS array and detection results[88]. (a) Layout of the DAS array; (b) location of the quarry relative to the DAS array; (c) average velocities measured in three segments before and after excavation
Fig. 19. Simulated rockfall monitoring results[90]. (a) Rockfall along the railway; (b) rockfall monitoring waterfall
Fig. 20. Traffic changes before and after blockade based on DAS[94]. (a) Average daily traffic volume change; (b) average traffic speed change
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Table 1. Classification and comparison of sensing principles based on LFM pulse DAS
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Table 2. Development of DAS performance indicators based on LFM pulse
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