| 摘要 |
PROBLEM TO BE SOLVED: To decrease the structural mismatching loss by controlling the transmission loss to a specified value or smaller when a red LED of a specified wavelength is used as the light source, and controlling the difference between the transmission loss measured for incident light of a specified wavelength with a specified numerical aperture and the transmission loss for the incident light with another specified numerical aperture to a specified value or smaller. SOLUTION: In an all-plastic optical fiber essentially comprising a three-layer structure of a core layer, sheath layer and protective layer, the transmission loss is specified to <=210 dB/km when a red LED of 660 nm wavelength is used as the light source. The difference between the transmission loss measured for incident light of 650 nm wavelength with 0.65 numerical aperture (N.A.) and the transmission loss measured for the incident light with 0.1 N.A is specified to <=10 dB/km. The melt index (M.I) under 5 kg load at 230 deg.C of each polymer used to form the layers satisfies that M.I of the polymer for forming the core <M.I of the polymer for the sheath×5/9 and M.I of the polymer for forming sheath < M.I of the polymer for forming the protective layer×7/9. |
