A new approach to prepare graded refractive index polymer optical fibers by extrusion of PMMA rods

High bandwidth, Graded-index (GRIN) polymer optical fiber has emerged as a very attractive application tool in optical communications. Two kinds of materials are generally used as GRIN materials: glass and polymers. Polymers have the advantages of excellent mechanical properties, molecular design flexibility, and easy processability. The purpose of this project was to develop Graded-index polymer fibers by the extrusion process. The materials used in this investigation were base polymer of polymethylmethacrylate (PMMA) and a refractive index modifier. Two different formulations having refractive index modifier compositions of 5% and 10% were used. A proprietary method was used to obtain a concentration gradient of the refractive index modifier. Special cutting and polishing methods were developed in order to test the rods. The refractive index profile was measured by the reflection method. Scanning Electron Microscopy along the diameter was used to study the concentration profile of the dopant. A significant parabolic curve was obtained for dopant distribution by the proprietary method. The basic extrusion process parameters for the fabrication of the PMMA fibers were established.