LAUSR

In this paper, a regular octagonal photonic crystal fiber (ROPCF) is proposed to support and improve the stable transmission of orbital angular momentum (OAM) modes. The proposed ROPCF is composed of a doped high refractive index ring and four layers of air hole rings, ensuring that the effective refractive index difference between OAM modes of the same order or OAM mode group is greater than 10−4 , and can stably transmit 114 OAM modes in the wavelength range of 1.5 ∼ 1.6 μm . A finite element method (FEM) is used to analyze the designed ROPCF. The measured results show that the ROPCF has high mode quality (MQ) (all modes are greater than 95%), and the confinement losses (CL) of all vector modes are in the range of 10−14 to 10−11 dB/m. In addition, it also has a large effective mode area between 197.64 to 297.82 μm2 . Moreover, the nonlinear coefficients and chromatic dispersions (CD) are less than 0.6 W−1/km and 276 ps/nm/km, respectively. And the dispersion change is relatively flat. The 10ps walk-off lengths of all vector modes supported by ROPCF at a wavelength of 1.55 μm are also analyzed. The obtained data results show that the 10ps walk-off lengths of the most of supported vector modes are within the range of 103 to 105 m, which is beneficial for long-distance transmission of OAM modes. These significant performances indicate that ROPCF has great application value in improving communication channel capacity (CC) and spectral efficiency (SE).