Design of Photonic Crystal Fiber Supporting 190 Orbital Angular Momentum Modes with Low Nonlinearity Coefficient

A new photonic crystal fiber is proposed for the transmission of more orbital angular momentum modes with a rectangular air hole arrangement to increase the cladding air-filling rate. The results reveal that the fiber can support 190 orbital angular momentum modes in the C+L band, with the topological charge ordering up to 48, and the effective refractive index difference between adjacent eigenmodes is above 10−3. The effective mode area of all the eigenmodes is larger than 208.02 μm2, the nonlinearity coefficient is less than 0.43W−1∙km−1, the confinement loss reaches up to 10−12-10−8 dB/m, the dispersion is flat and the minimum dispersion change is 3.15ps∙nm−1∙km−1, with mode purity greater than 97.4%. Compared to existing typical orbital angular momentum transmission photonic crystal fibers, this fiber can support more orbital angular momentum modes for most purposes with lower nonlinearity coefficient, higher mode purity, better propagation characteristics but simpler structure. The highest nonlinearity coefficient is reduced by at least 0.3W−1∙km−1 compared to existing typical orbital angular momentum transmission photonic crystal fibers. The effect of fabrication errors on the transmission quality of orbital angular momentum modes is also discussed, and the results reveal that the effect on mode transmission quality is small at 1% to 2% variations of air holes. Therefore, this photonic crystal fiber is promising in high-capacity communication systems.