Fig. 1. Schematic of the step-index fiber structure. (a) Cross section; (b) refractive index distribution of cross section

Fig. 2. Variation of the n_eff with r₁ at the λ=1550 nm

Fig. 3. Power distribution of 14 modes of the FMF

Fig. 4. Structure of double-clad FMF. (a) Cross section; (b) refractive index distribution of cross section

Fig. 5. Minimum Δn_eff versus the core radius r₁ and relative refractive index difference Δ. (a) r₁=9--10 μm,Δ=1.5%--1.75%; (b) r₁=9--9.4 μm,Δ=1.67%--1.75%

Fig. 6. Variation of the n_eff and Δn_eff with d/r₁ at the λ=1550 nm. (a) n_eff; (b) Δn_eff

Fig. 7. Mode field distribution of 14 modes at d=253 nm

Fig. 8. Power distribution of 14 modes of nanopore-assisted FMF

Fig. 9. Wavelength dependence of n_eff and Δn_eff of traditional step index fiber and nanohole-assisted fiber. (a) Wavelength dependence of n_eff of the traditional step index fiber; (b) wavelength dependence of Δn_eff of the traditional step index fiber; (c) wavelength dependence of n_eff of the nanohole-assisted fiber; (d) wavelength dependence of Δn_eff of the nanohole-assisted fiber

Fig. 10. Dependence of bending loss on double-cladding parameters. (a) Dependence of bending loss on W; (b) dependence of bending loss on Δ₁; (c) dependence of bending loss on D

Fig. 11. Variation curve of bending loss versus bending radius. (a) Fiber without grooves; (b) fiber with grooves

Fig. 12. Effective mode field area dependence on the parameters of double-clad. (a) Dependence of the effective mode field area on W; (b) dependence of the effective mode field area on Δ₁

Fig. 13. Dependence of the DMD of the optical fiber on the wavelength

Fig. 14. Dependence of fiber dispersion on wavelength