Xiang Zhong, Shisong Zhao, Huaxia Deng, Jin Zhang, Mengchao Ma. Review of research on Φ-OTDR system based on pulse modulation[J]. Infrared and Laser Engineering, 2020, 49(10): 20200166
- Infrared and Laser Engineering
- Vol. 49, Issue 10, 20200166 (2020)
Fig. 1. Schematic of Φ -OTDR system
![Interference visibility of the system at different pulse widths[9]](/richHtml/irla/2020/49/10/20200166/img_2.jpg)
Fig. 2. Interference visibility of the system at different pulse widths[9]
![Law of signal to noise ratio vs pulse width[10]](/Images/icon/loading.gif){kind=icon}
Fig. 3. Law of signal to noise ratio vs pulse width[10]
Fig. 4. Numerical simulation of standard deviation of the strain level and pulse width[11]
Fig. 5. FRC of different frequency drift rates and pulse widths[12]
Fig. 6. Backscattering power traces from different pulse shapes with magnification of traces[14]
Fig. 7. Rayleigh backscattering traces of 1.5 km FUT. (a) High extinction-ratio pulse; (b) Direct-modulation pulses[16]
Fig. 8. Schematic of the pulse-width multiplexing method[21]
Fig. 9. 0-π binary phase shift pulse. (a) Phase-shifted double pulse method[24]; (b) Differential phase shift pulsing technology[25]
Fig. 10. Composite double probe pulse[27]
Fig. 11. Spectrum of NLFM optical pulse[28]
Fig. 12. Linear frequency modulates light pulses. (a) Time-domain profile; (b) Compressed profile[29]
Fig. 13. Optical pulse train. (a) Pulse shape for Φ -OTDR and MZI multiplexing system[33]; (b) Pulse shape for Φ -OTDR and polarization diversity multiplexing system [33-34]
Fig. 14. (a) Pulse train in conventional Φ -OTDR; (b) Pulse train in frequency division multiplexing Φ -OTDR; (c) Frequency variation of pulse train[35]
Fig. 15. Three groups of consequent double pulses[40]
Fig. 16. Dual-pulse using frequency division multiplexing. (a) Modulation on tunable laser source; (b) Modulation on AOM[44]
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