The subject invention pertains to a method and apparatus for manufacturing a plastic optical
transmission medium. The subject invention also relates to materials for use in producing plastic optical
transmission medium. The subject method can allow continuous high-speed production while controlling the
refractive index profile, step or graded, of the optical
transmission medium. In a specific embodiment, the medium POTM can have high optical transmission, and be able to operate in conditions up to 125° C. at 95% R.H. In a specific embodiment of the subject invention, two or more concentric cylinders of transparent
polymer melts, of which at least one is a cross-linkable material, can be utilized to produce a plastic optical transmission medium. In addition, zero, one, or more transparent, nonreactive, low molecular weight diffusible additive(s) can be added to zero, one, or more of the transparent
polymer melts to provide a graded
refractive index profile. The molecular weights and chemical structures of the index modifying additives can be chosen to ensure their
diffusion constants are low enough to provide a stable
refractive index profile at the desired
operating temperature of the
fiber. The cylinders of melt can be extruded into a solidified polymeric tube via, for example, a cross-head type of die. The tube containing the melt materials can be maintained at high temperature for a
specific time period, such that the cross-linking can occur and, optionally, the additives can diffuse within the polymeric tube.