Control of refractive index distribution for high-bandwidth graded index plastic optical fiber

Makoto Asai, Kazuma Nehashi, Yasuhiro Koike

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)


The graded index plastic optical fiber (GI-POF) has been proposed as the transmission medium to realize high-speed information transmission. We have succeeded in fabricating a GI-POF by the coextrusion process, a method that allows continuous fabrication of GI-POF. Although it has been indicated that the refractive index distribution of GI-POF fabricated by this process is formed by Fick diffusion with diffusion coefficient dependent on dopant concentration, the method to control it remains unknown. The purpose of this paper is to establish the technology of controlling refractive index distribution in GI-POF fabricated by the coextrusion process. Therefore, we investigate the physical mechanism of the dependency of diffusion coefficient on dopant concentration. It has become clear that the dependency is affected by the decrease of glass transition temperature and the nonlinear increase of melt flow rate. Moreover, through simulation of dopant diffusion by our originally developed program, it has become evident that changing the molecular weight of the core and cladding material allowed control of fabricating a GI-POF with optimal refractive index distribution by this fabrication method.

Original languageEnglish
Pages (from-to)2909-2918
Number of pages10
JournalJournal of Lightwave Technology
Issue number16
Publication statusPublished - 2008 Aug 15


  • Bandwidth
  • Equations
  • Friction
  • Heating
  • Mathematical model
  • Plastics
  • Refractive index

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics


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