| 摘要 |
PURPOSE:To reduce transmission loss of light and unevenness of fiber and to improve productivity of the optical fiber by drawing the optical fiber to >=1 and <=10 draw ratio in the production of plastic multi optical fiber having a section constituted of a sea-island structure by using a far infrared heater for preheating in combination with a near infrared heater for drawing of neck parts of the optical fiber. CONSTITUTION:Optical fiber 6 is transported through a nip roller 1 at a feed side of the fiber to a far infrared heater 3 covered with a cover when plastic multi optical fiber having a section constituted of a sea-island structure is produced, and the fiber 3 is preheated with a heater 3. The preheated fiber 6 is transported to a position where a near infrared heater 4 is provided, and the neck parts of the fiber are drawn with the heater 4. Then, the drawn fiber including the neck parts are cooled in a cooling device 5 and wound around a nip roller 2 at a take-up side to draw thus the fiber 6 with 1-10 draw ratio. Thus, nonuniformity of the optical fiber due to the change of draw ratio in the inside of core is eliminated. Transmission loss of light is also reduced and the productivity of the fiber is improved.
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