Finite element analysis of open‐type waveguides with homogeneous cladding by the use of multipole expansion

Abstract

AbstractOpen‐type waveguides with homogeneous cladding can be analyzed by the finite element method (FEM) with the multipole expansion method. In this paper, we propose a new connection method in which the fields described by the FEM and by the multipole expansion are combined at the connection boundary between the finìte inner region and the infinite outer region by using Galerkin method. By means of this method, we can analyze open‐type waveguides with higher accuracy and less amount of calculation than conventional FEM. In addition, there is no difficulty arising from spurious mode and no restriction between the number of the basis functions of the FEM and that of the multipole expansion functions on the connection boundary. The final matrix equation is symmetric. The validity and usefulness of the method has been demonstrated in the example of a rectangular dielectric waveguide and an elliptical fiber.