Circular photonic crystal fiber supporting 118 orbital angular momentum modes transmission

Circular photonic crystal fiber consisting of doped amethyst and big and small round air holes is designed to support transmission of 118 orbital angular momentum (OAM) modes in the range of 1.2 to 1.65  μm. Numerical analysis by the finite element method (FEM) reveals that the effective index difference of all the modes are larger than 1  ×  10  −  4, which can propagate OAM modes stably. The nonlinear coefficient is 0.583  W  −  1 km  −  1 at 1.55  μm, which is very low and helps to reduce mode coupling. In addition, the confinement loss of the eigenmode is between 10  −  12 and 10  −  8  dB  /  m. The dispersion is very flat for the low-order mode HE1,1, for which the dispersion variation is just 1.459  ps  /    (  km nm  )  . This fiber has great potential in stable and large-capacity mode propagation in optical communication.