Fig. 1. Schematic diagram of ECOF structure. (a) Schematic of cross section; (b) refractive index profile

Fig. 2. Structural parameter min Δn_eff versus the core radius R₁ and relative refractive index difference Δ

Fig. 3. Mode field distribution of ten modes at the core radius R₁=10.2 μm and relative refractive index difference Δ=0.94%

Fig. 4. Relationship between effective refractive index and wavelength at R₁=10.2 μm and Δ=0.94%. (a) Variation of n_eff with wavelength; (b) variation of Δn_effwith wavelength

Fig. 5. Relationship between the effective refractive index of ten modes and eccentric distance. (a) LP₅₁; (b) LP₀₃; (c) LP₂₂; (d) LP₄₁; (e) LP₁₂; (f) LP₃₁; (g) LP₀₂; (h) LP₂₁; (i) LP₁₁; (j) LP₀₁

Fig. 6. Relationship between normalized intensity and eccentric distance. (a) Core region; (b) coating region

Fig. 7. Relationship between normalized optical intensity and refractive index of coating at different eccentric distances. (a) L=52.3 μm; (b) L=50.3 μm; (c) L=48.3 μm; (d) L=0 μm

Fig. 8. Relationship between bending loss and bending radius at different bending orientations. (a) Bending direction of 0°; (b) bending direction of 180°