Abstract This article presents the theoretical analysis of a signal coupling between a proposed Photonic Crystal Fiber (PCF) and a Conventional Fiber with Step Index (CFSI) system. In this analysis, the Finite Element Method (FEM) and Beam Propagation Method (BPM) are applied together with Daubechies wavelets as basis function and described in the mathematical formulation. The simulations were performed casting the PCF signal into CFSI core using the PCF refractive index. For simulation purposes, the cladding material refractive index was set as 1.5% lower than the core index. The application of Daubechies wavelets as basis functions in BPM analysis presented insertion loss around 3.8% during the fiber coupling.