Fig. 1. Schematic diagram of DPP-BOTDA bending measurement system

Fig. 2. Schematic diagram of differential pulse pairs

Fig. 3. Simplified model of distributed bending sensor

Fig. 4. DPP-BOTDA experimental measurement sensing system

Fig. 5. MCF internal structure

Fig. 6. Time-domain analysis results for core 1 and core 7 at 70 ℃. (a) Three-dimensional Brillouin gain diagram of core 1; (b) top view of Brillouin gain diagram of core 1; (c) three-dimensional Brillouin gain diagram of core 7; (d) top view of Brillouin gain diagram of core 7

Fig. 7. Temperature fitting curves for cores 1, 3, 5, 7

Fig. 8. Cores 1, 3, 5, 7 temperature compensated bending measurements. (a) BFS of four cores 1, 3, 5, 7 at positions 16.5‒19.5 m; (b) temperature information obtained by solving core 1; (c) changes in BFS of cores 3, 5, 7 after subtracting effect of temperature

Fig. 9. Strain curves for cores 3, 5, 7

Fig. 10. Curvature of bending section of an optical fiber