Circular photonic crystal fiber supporting 110 OAM modes

We propose a new circular photonic crystal fiber (CPCF), which can support orbital angular momentum (OAM) modes as many as 110 in C and L communication bands. Using finite element method (FEM), the characteristics of the CPCF for different OAM modes are systematically studied. The numerical analysis shows that most eigenmodes effective index differences are at the order of 10−3, which is helpful to reduce the mode coupling and ensure stable OAM modes transmission. Moreover, the nonlinear coefficient is relatively low, with the values for most modes are within 2.80 W−1∕km at 1.55 μm. In addition, the confinement loss of most eigenmodes possesses low values under 10−7 dB/m. Besides, all of the OAM modes have relative flat dispersion. In brief, the designed CPCF features large effective index contrast, small nonlinear coefficient, low confinement loss and relatively flat dispersion, which could find potential application in high capacity OAM mode division multiplexing (MDM) fiber communication systems.