Fig. 1. Diagram for the HC-LPFG structure

Fig. 2. Simulation results of the HC-LPFG fiber structure. (a) Optical field distribution in the X-Z plane; (b) optical field distribution in the X-Y plane; (c) comparison of simulated and experimental transmission spectra of HC-LPFG

Fig. 3. Fabricating system for the HC-LPFG structure

Fig. 4. Structure diagrams of HC-LPFG. (a) Phase-contrast image; (b) microstructure diagram

Fig. 5. Transmission spectrum of HC-LPFGs with different helical length. (a) Sample 1; (b) sample 2; (c) sample 3

Fig. 6. Schematic diagram of sensing characteristic measuring devices for HC-LPFG

Fig. 7. Torsion measurement experiment results of sample 1. (a) Spectral shift; (b) linear relationship

Fig. 8. Experimental results of HC-LPFG. (a) Temperature response; (b) strain response