PURPOSE: To enable prepn. of stress-relieved clad optical fiber core having superior reliability by cladding a plastic material having low elastic modulus on the outside of optical fiber and cooling in a low temp. bath, and cladding further with a plastic material having high elastic modulus.
CONSTITUTION: Two component type silicon is supplied from a feeding device 13a, 13b through a gear pump 14, and a mixer 15 to a cross head 6 for cladding in order to clad optical fiber 1 supplied from a feeding device 4. A first clad layer 2 is formed from two component setting type silicon gel having low modulus of elasticity in the cross head 6 on the optical fiber 1. After cooling the product in a cooling tank 19 with liquid N2, the fiber is further clad with a plastic layer 3 having high elastic modulus such as nylon 12, etc. in the cross head 8, and is cooled in a water cooling tank 9, and is wound by a winder 5 through a capstan take-off machine 10. No void is formed in the silicon gel layer by this method, and clad optical fiber core having superior reliability is obtd.
FUSE KENICHI
OKAGAWA SHIYUUJI
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