Abstract: A mandrel for producing a large quartz glass body, comprising at least two columnar or cylindrical, carbon fiber-reinforced carbon composite members and joined in series by screw thread parts, wherein preferably the contact surface of the screw thread parts of the mandrel is impregnated and/or coated with carbon, and more preferably a reinforcing member made of a C/C composite is provided on the outer periphery of the screw thread parts.

Abstract: A mandrel for producing quartz glass, comprising at least two columnar or cylindrical, carbon fiberreinforced carbon composite material made members joined in series by screw thread parts. The mandrel is carbonimpregnated and/or carbon-coated on the screw thread parts, and, in addition, may be provided with reinforcing members on the outer sides of the screw thread parts. Quartz glass fine particles obtained by flame-hydrolyzing a volatile silicon compound are deposited, using this mandrel, on the surface of a heat-resisting substratum or on a starting rod at the end of the mandrel to easily form a large porous quartz glass mother material, the porous quartz glass mother material is dehydrated and transparently vitrified to produce a large optical fiber mother material, and further the optical fiber mother material is drawn to produce a low-cost, high-precision optical fiber.

Abstract: A mandrel for producing quartz glass, comprising at least two columnar or cylindrical, carbon fiberreinforced carbon composite material made members joined in series by screw thread parts. The mandrel is carbon-impregnated and/or carbon-coated on the screw thread parts, and, in addition, may be provided with reinforcing members on the outer sides of the screw thread parts. Quartz glass fine particles obtained by flame-hydrolyzing a volatile silicon compound are deposited, using this mandrel, on the surface of a heat-resisting substratum or on a starting rod at the end of the mandrel to easily form a large porous quartz glass mother material, the porous quartz glass mother material is dehydrated and transparently vitrified to produce a large optical fiber mother material, and further the optical fiber mother material is drawn to produce a low-cost, high-precision optical fiber.