| abstract |
In a coating apparatus, low density polyethylene (122) is flowed in the resin passage (123, 124) between a die (120) and a nipple (121) to form an optical fiber strand having a protective layer (129) on the POF (14). The die (120) and the nipple (121) satisfy the following conditions: D ≤ TA ≤ 1.3D TA ≤ L ≤ 4TA 0.7TA ≤ TB1 ≤ 1.3TA (D1+10) μm ≤ TB2 ≤ (D1+300) μm TA ≤ d ≤ 2TA in which TA (μm) indicates the diameter of the die (120), TB1 (μm) indicates the diameter of the nipple (121), TB2 (μm) is the inner diameter of the nipple (121),D1 (μm) is the diameter of the POF (14), D (μm) is the diameter of the optical fiber strand, and d (μm) is the clearance between the die (120) and the nipple (121). |