PURPOSE: To coat the outer circumference of an optical fiber with a reinforcing metallic layer, uniformly and continuously, by contacting a spun optical fiber with metallic vapor in a metallic vapor pipe.
CONSTITUTION: A ring-shaped metal-melting crucible 21 having a hollow part at the center is integrated with a vertical pipe 22 for passing metallic vapor, and is placed in the path of the spun optical fiber 3. The crucible 21 is charged with a metallic coating material having relatively high vapor pressure, and an inert gas is introduced through the gas-feeding pipe 23 into the crucible 21 to keep the atmosphere in the crucible 21 to non-oxidative state. The coating material 24 is molten and evaporated by the first furnace 24, and the metallic vapor is filled in the pipe 22 heated by the second furnace 25. The optical fiber 3 is inserted into the pipe 22, brought into contact with the metallic vapor to deposite metallic layer on the surface, and pulled down through the hollow part of the crucible 21 to obtain an optical fiber 3' having uniformly applied metalic layer.
YUASA MITSUO
TSUKAMOTO MAKOTO
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