Fig. 1. 3D shape reconstruction technology flow chart

Fig. 2. Schematic diagram of the seven-core optical fiber sensing principle. (a) Curvature; (b) Torsion

Fig. 3. Schematic diagram of 3D shape reconstruction

Fig. 4. Simulation results of different grating spacings. (a) Diagram of 3D reconstruction effect; (b) Spatial position error; (c) Relationship between grating spacing and error curve slope

Fig. 5. Experimental setup for 3D shape sensing. (a) Schematic diagram of the system; (b) End face of seven-core fiber; (c) Optical fiber with ribbon structure; (d) 3D helical curvature groove

Fig. 6. (a) Grating spectrum of each fiber core; (b) Spectrum of grating string

Fig. 7. 3D shape sensing experiment. (a) Reconstructed curve and true curve; (b) Error