| CPC C03B 37/12 (2013.01) [C03C 25/105 (2013.01); G02B 6/02395 (2013.01)] | 10 Claims |
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1. A method for screening an optical fiber core including a resin coating layer, the method comprising:
a pre-strain applying step of adding a tensile force while feeding a portion of the optical fiber core retained at both ends of the portion, and applying a pre-tensile strain larger than zero and smaller than a guaranteed tensile strain set as a guaranteed value, the optical fiber core including the resin coating layer and being wound by a bobbin and fed out from another bobbin;
a guaranteed strain applying step of adding a tensile force while feeding the portion of the optical fiber core retained at both ends of the portion and applied with the pre-tensile strain, and applying the guaranteed tensile strain only for a predetermined time; and
a guaranteed strain releasing step of releasing the optical fiber core from the guaranteed tensile strain, wherein:
at the pre-strain applying step, the pre-tensile strain is applied by applying tensile strain stepwise,
at the pre-strain applying step, when applying the tensile strain in N stages (N is an integer of 2 or more), and a tensile force added at the n-th stage (n is an integer of 1 or more and less than N) is set to the tensile force n, the tensile force is added so as to achieve the relationship of (tensile force 1)>(tensile force (n+1)−tensile force n).
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