PRODUCTION OF OPTICAL FIBER FOR INFRARED LIGHT

摘要

PURPOSE:To eliminate the change of the characteristic of a polycrystalline optical fiber for IR light in the lapse of time and the abnormality thereof and to form the highly flexible fiber by executing the hot extrusion of a preform crystal made of a metallic halide in a gas which does not contain oxygen and hydrogen. CONSTITUTION:An introducing port 9 for the gas is provided above a housing 8 and a lead-out port 10 for the optical fiber 6 is provided below the housing. The dry gaseous nitrogen 11 can be supplied from a dry gaseous nitrogen supplying device to be provided at the other plate through a piping 9' and the port 9. The optical fiber for IR light is extruded into the gas which does contain oxygen and moisture in the case of using the metallic halide as the stock and producing the optical fiber for IR light by hot extrusion. The blackening of the outside peripheral surface thereof and the blackening of the crystal grain boundary are thereby prevented. The transmission loss of the IR light in the lapse of time is decreased and the bending limit is improved by extruding the optical fiber for IR light while blowing the gas which does not contain oxygen and hydrogen to the base of a die for hot extrusion including a mouth for extruding the optical fiber.