Fig. 1. Schematic diagram of shaped BOTDA system based on stimulated Brillouin scattering

Fig. 2. Simplified theoretical model of distributed shape sensor

Fig. 3. BOTDA shape measurement system diagram

Fig. 4. Internal structure diagram of seven-core optical fiber

Fig. 5. Brillouin gain spectrum of multi-core fiber during bending

Fig. 6. Brillouin gain spectrum in 290~300 m bending section of multi-core fiber

Fig. 7. Brillouin frequency shift in sensing fiber segment

Fig. 8. Change in Brillouin frequency shift for each off-core

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

Fig. 10. Curvature$\kappa$of the bending section of multi-core fiber

Fig. 11. The bending section reconstructs the shape of a circle