Fig. 1. The cross section of the ring fiber and electric field intensity distribution of each vector mode. (a) Cross section of the OAM photonic crystal fiber; (b) electric field intensity distribution of each vector mode

Fig. 2. Corresponding field distribution and phase distribution

Fig. 3. Relationship between parameters of vector eigenmode. (a) Relationship between effective refractive index and wavelength; (b) relationship between effective refractive index difference and wavelength

Fig. 4. Relationship between effective index difference of each mode and D and d_c. (a) D; (b) d_c

Fig. 5. Relationship between the effective refractive index difference of each vector mode of two kinds of photonic crystal fibers and wavelength

Fig. 6. Loss characteristics of different types of optical fibers. (a)Confinement loss of different modes under different cladding air hole structures; (b) relationship between confinement loss of each mode and wavelength

Fig. 7. Birefringence of vector modes at 1.55 μm corresponding to various bending radii. (a) Bending diagram; (b) effective refractive index and field distribution of HE11odd and HE11even modes when the bending radius is 1 mm and 18 mm; (c) variation of refractive index difference of selected vector modes with bending radius