Development of graded Index plastic optical fibers by controlling composition profile of copolymers

Abstract

The polymer optical fiber (POF) is a strong candidate for next generation optical transmission medium of high data transmission rate. In this thesis, after introduction to the general aspect of the polymer optical fiber including the advantages, the problems, the production method and the optical measurements, it has been investigated that three different methods for production of the PMMA-based copolymer gradient refractive index (GRIN) preform possessing a parabolic-like refractive index gradient The first method for the fabrication of the graded index-polymer optical fiber (GI-POF) is the laminar shear mixing (LSM) method. A GRIN preform was successfully prepared by using LSM, and the GI-POF satisfied IEEE1394b specification was obtained. To fabricate the GRIN rod a liquid monomer mixture with a relatively low refractive index was placed in a prepared cylindrical glass reactor, and a transparent polymer rod with a higher refractive index was introduced at the center of the reactor. The reactor and the polymer rod were then rotated concurrently with a small rotating speed difference to generate a Couette flow in the liquid phase. The centrifugal force generated by rotation and the polymer diffusion into the liquid monomer mixture developed a graded concentration profile in a radial direction. The Couette flow could reduce the concentration fluctuation in a tangential direction. In addition, the graded index profile could be controlled by the copolymer composition of the rod and its diameter. The second method to manufacture the GI-POF is the use of automatic refilling (AR) reactor. In order to overcome the volume shrinkage problem of the bulk radical polymerization of an acrylic monomer during manufacturing of the preform with radial GRIN for the PMMA-based GI-. POF, it was designed the novel cylindrical reactor with a three dimensional structure which can prevent the vacancy due to the volume shrinkage from propagating into the main reaction part of the reac...