Fig. 1. Schematic diagram of the molecular energy level transition in Raman scattering

Fig. 2. Principle of OTDR technology

Fig. 3. Principle of OFDR technology

Fig. 4. Flow chart of demodulation process

Fig. 5. Schematic diagram of the double-ended detection structure of RDTS system

Fig. 6. Structure optimization of the RDTS system with mirrors^[37]

Fig. 7. Experimental setup of Cyclic pulse coding technology^[50]

Fig. 8. Schematic diagram of chaotic laser based RDTS system^[56]

Fig. 9. Schematic diagram of RDTS system device based on fiber optic cascade^[45]

Fig. 10. Comparison of temperature measurement accuracy before and after M factor calibration under three different measurement methods^[66]. (a) Result of dual-demodulation based on single-ended detection structure; (b) result of self-demodulation based on single-ended detection structure; (c) result of double-ended detection

Fig. 11. Temperature measurement results compared to the original data (blue) after denoising by the NLM algorithm (red) ^[77]. (a) SNR; (b) temperature resolution

Fig. 12. Network structural diagram of the 1DDCNN ^[79]

Fig. 13. 15 cm long heated area reconstructed using total variational deconvolution^[21]

Fig. 14. Current situation and forecast of global and Chinese DTS market scale^[91]

Fig. 15. Application of RDTS system in embankment dams safety and pipeline leakage monitoring. (a) Schematic diagram of the dam safety monitoring application structure^[108]; (b) leakage test site^[114]; (c) schematic diagram of the pipeline leakage monitoring^[125]; (d) pipeline leakage monitoring site^[124]

Fig. 16. Application of RDTS system in power system safety monitoring. (a) Integration of optical fiber in the cable^[135]; (b) thermal conductivity model of the overhead cable ^[138]; (c) application in photovoltaic panel temperature monitoring^[139]; (d) application in motor temperature monitoring^[140]

Fig. 17. Application of RDTS system in the tunnel fire detection^[68]

Fig. 18. Application schematic diagram of of RDTS system in oil well ^[146]

Fig. 19. Application of RDTS system in high and low temperature sensing. (a) Measured temperature distribution using gold-coated fibers at different temperatures^[163]; (b) measured temperature distribution of the scatterer at low temperature^[164]

Fig. 20. Application of RDTS system in nuclear industry safety monitoring. (a) Schematic diagram of application in nuclear radiation field^[168]; (b) schematic diagram of the structure used for the safety monitoring of radioactive waste ^[170]