PURPOSE: To prevent deterioration of an optical fiber by cooling the optical fiber immediately before applying a tension, in case of screening of the optical fiber for securing a strength by making the optical fiber run in the longitudinal direction and applying a tension in its longitudinal direction.
CONSTITUTION: In a screening method of an optical fiber for securing a strength by making an optical fiber 2 run in the longitudinal direction, and applying a tension in its longitudinal direction, at least immediately before applying a tension, the optical fiber 2 is cooled. In this way, by cooling the optical fiber 2 before applying a tension, a Young's modulus of covering materials 9, 10 is increased, and a resistance force to a shearing stress working on the covering materials 9, 10 can be increased. In this way, even if a screening test of a high level which brings on a tensile strain of ≥2% is executed, the covering materials 9, 10 are not deteriorated, and an increase of a transmission loss is not generated.
KATOU KOUJI
NISHIMOTO MASAYUKI
TAJIMA YOSHIMITSU
NIPPON TELEGRAPH & TELEPHONE