Computing of mode structure transmission parameters in commercially available optical fiber samples with large core diameter

This work presents a method of dispersion parameters computing for guided modes propagation in commercially available telecommunication silica optical fibers with a large core diameter. These real optical fibers differ from ideal model representation by non-symmetric geometry of transversal cross-section in both radial coordinates and refractive index profile. We propose a solution for detailed reconstruction of a 3D-structure for the studied optical fiber under the condition of limited data availability gathered from refractive index profile measurement protocols conducted by conventional lab kits for optical fiber analysis over conditional transversal cross-sections “X” and “Y”. The proposed solution is based on the irregular mesh with nodes located at cross-section semi-axes corresponding to refractive index profile extremums. This allows an implementation of triangularization procedure to build an adaptive mesh for representation of a studied fiber during its analysis by rigorous numerical methods. We performed a computing of guided mode structure transmission parameters for commercially available sample of multimode optical fiber 50/125 of Cat. OM2 with big core asymmetry and strong refractive index profile distortions using recently developed modification of mixed finite element method adapted for analysis of optical fibers with a large core diameter. Computation results were compared with analytical data obtained for an ideally symmetric multimode optical fiber model with structure repaired and also with the measurement data for the case of only one semi-axis.