A novel nested three-ring-core photonic crystal fiber for OAM transmission

A novel nested three-ring-core photonic crystal fiber (PCF) is designed and analyzed. OAM modes are transmitted independently in the three guided mode regions and the nested structure increases the number of OAM modes. In the wavelength range of 1.5–2.0 µm, the PCF shows stable transmission of 46 + 62 + 74 OAM modes. The mode purity of all the eigenmodes is greater than 91% and the isolation parameters remain above 55 dB. The larger effective mode field areas result in ultra-low nonlinear coefficients less than 1.04 m²W⁻¹ and the confinement losses of the supported modes are less than 1.18 × 10⁻⁸ dB/m. In addition, the structure comprising circular air holes and silica enables easier manufacturing and the excellent performance also suggest large potential in large-capacity transmission systems.