Based on the Helmholtz equations, the full-vector finite element method (FEM) accompanied with the shifted iteration algorithm is used to analyze in-phase supermodes of a 19-core photonic crystal fiber. The effects of fiber structural parameters on the in-phase supermode field are also studied. The results indicate that the form of the fiber structure plays a key role on coupling of fiber cores, and the desired mode shapes which have the same amplitude in each core can be obtained by choosing the appropriate diameter of airhole. The results show a viable option for further achieving high-power laser output.
