Fig. 1. Change curves of BGS and LCF

Fig. 2. Schematic of ANN^[30]

Fig. 3. Fiber temperature distribution diagram extracted by ANN under different frequency sweep intervals, where temperature of fiber at 41 m of tail is (a) 21.00 ℃ (room temperature), (b) 29.90 ℃, (c) 39.14 ℃, and (d) 48.63 ℃^[30]

Fig. 4. Ratio of time spent in processing BGS data between LCF and ANN^[30]

Fig. 5. Schematic of SVM extraction temperature^[32]

Fig. 6. Measured BGS distribution and temperature distribution extracted by SVM-0.5 °C^[32]

Fig. 7. Uncertainty and RMSE comparison curves under different SNR^[32]. (a1) (a2) 11.5 dB; (b1) (b2) 6.1 dB

Fig. 8. Structure and extraction principle of DNN^[35]. (a) DNN structure; (b) schematic of extracting temperature and stress at the same time by DNN

Fig. 9. Experimental device of LEAF and comparison curves of extraction results of different methods^[35]. (a) Experimental device; (b) comparison curves of temperature and stress under DNN and equation solving method

Fig. 10. BGS signal processing flow based on K-SVD algorithm ^[37]

Fig. 11. Temperature error curves of K-SVD algorithm and LCF algorithm^[37]

Fig. 12. ELM training and testing process^[38]

Fig. 13. CNN structure for extracting BFS ^[40]

Fig. 14. Comparison of BFS results after CNN and LCF algorithm processing^[40]