PURPOSE: To prevent intrusion of foam into a resin coated film and to prevent deterioration, etc. of a transmission characteristic in the stage of passing an optical fiber through the inside of a resin tank in which a resin for coating in a fluid state is filled by maintaining the inside of the resin vessel in a vacuum.
CONSTITUTION: A resin 3 for coating in a fluid state is filled in a resin vessel 2 and the inside of the tank 2 is evacuated to a vacuum by a vacuum pump 5 to maintain the inside of the tank 2 at a specified degree of vacuum. A spun and drawn optical fiber 1 is then introduced into the tank 2 where the fiber is passed from above to below to coat the resin on the outside circumference of the fiber 1. The air sticking to the side face of the fiber 1 is thus thoroughly removed by the vacuum before the fiber 1 enters the inside of the resin 3 in the tank 2. The resin coated film contg. no foam is formed on the outside circumference of the fiber 1 and a coated fiber 4 is obtd. without deteriorating the transmission characteristic, mechanical characteristic, etc. thereof.
ABE KOUICHI
SOTODANI SHIGEO
