Method of manufacturing a preform for a refractive index distributed type plastic optical fiber

摘要

A preform having a core and a cladding portion is prepared for a refractive index-distributed type plastic optical fiber. The fiber obtained has a large difference in refractive index between the central and peripheral zone of the core portion. This suppresses light propagation modes in the cladding portion, a cause of deteriorated transmission characteristics, without raising the concentration of non- polymerizable compounds contained in the core portion. To manufacture the preform, a cylindrical vessel is prepared from a polymer, which serves as cladding portion. The inner surface of the preform is then provided with a polymer-containing layer having a refractive index lower than that of the polymer used for the core portion, so as to leave a cavity inside this vessel. This cavity is then filled with a monomer, which is subsequently polymerized while dissolving the lower-refractive index, polymer-containing layer, so as to form the core portion.