Patent ID: 7813607

Claim:
An optical fiber bundle unit for transmitting ultraviolet light including: an optical fiber bundle; and a sealed container in which the optical fiber bundle is held, wherein a diffusion of hydrogen gas is suppressed by putting the optical fiber bundle, exposed to a hydrogen atmosphere in which the pressure is set to 10 to 500 kgf/cm 2 and the temperature is set to 80 to 300° C., into the sealed container, followed by filling the sealed container with a mixed gas including a hydrogen gas and a gas which is not combustible, will not support combustion, and will not explode, the sealed container includes a cylindrical member and sealing members which seal both ends of the cylindrical member, and seals are formed between the cylindrical member and sealing members using a sealant, the concentration of the hydrogen gas relative to the total volume of the mixed gas is 4% and below by volume, and the pressure of the mixed gas is within a range from 10 to 500 kgf/cm 2 .