Fig. 1. Cross section and refractive index profile of ideal HRC-POF

Fig. 2. Cross section of HRC-POF with geometric deformation

Fig. 3. Number of OAM modes and Δn_{eff, min} versus degree of geometric deformation in the HRC-POF

Fig. 4. The effective refractive index difference between even and odd modes versus ellipticity and misalignment in HRC-POF

Fig. 5. Mode intensity distribution versus ellipticity and misalignment in HRC-POF

Fig. 6. Walk-off length versus ellipticity and misalignment in HRC-POF

Fig. 7. The minimum purity of synthesized OAM modes versus ellipticity and misalignment in HRC-POF

Fig. 8. The crosstalk level versus ellipticity and misalignment in HRC-POF