Abstract: A porous glass intermediate body constructed by a core original layer formed as a core portion of an optical fiber, and a first clad original layer formed as a first clad portion of the optical fiber is formed. Thereafter, a transparent glass intermediate body is made by consolidating the porous glass intermediate body within an atmospheric gas with a chlorine-based gas with no fluorine compound. Thereafter, a porous optical fiber base material is made by forming a second clad original layer as a second clad portion of the optical fiber on the circumferential surface of the transparent glass intermediate body. When a porous state is then maintained, the porous optical fiber base material is dehydrated within the atmospheric gas with a chlorine concentration higher than that during the consolidation of the porous glass intermediate body. Thereafter, an optical fiber base material is manufactured by consolidating the porous optical fiber base material within a similar atmospheric gas.

Abstract: A porous glass intermediate body constructed by a core original layer formed as a core portion of an optical fiber, and a first clad original layer formed as a first clad portion of the optical fiber is formed. Thereafter, a transparent glass intermediate body is made by consolidating the porous glass intermediate body within an atmospheric gas with a chlorine-based gas with no fluorine compound. Thereafter, a porous optical fiber base material is made by forming a second clad original layer as a second clad portion of the optical fiber on the circumferential surface of the transparent glass intermediate body. When a porous state is then maintained, the porous optical fiber base material is dehydrated within the atmospheric gas with a chlorine concentration higher than that during the consolidation of the porous glass intermediate body. Thereafter, an optical fiber base material is manufactured by consolidating the porous optical fiber base material within a similar atmospheric gas.

Abstract: An optical fiber preform is a material used for fabricating optical fibers. The optical fiber preform has a target rod which will be the core for optical fibers and a glass layer formed around the outside thereof. A mass W (kg) of the optical fiber preform and a diameter D (cm) of the target rod satisfy a relational expression 0.4·(W)1/2<D. Satisfying this relational expression can prevent the optical fiber preform from being deformed and to have uneven diameters due to the weight thereof in the dehydrating and consolidating process in fabricating the optical fiber preform, even though it is a large-sized optical fiber preform having a diameter of 10 cm or more.

Abstract: An optical fiber preform is a material used for fabricating optical fibers. The optical fiber preform has a target rod which will be the core for optical fibers and a glass layer formed around the outside thereof. A mass W (kg) of the optical fiber preform and a diameter D (cm) of the target rod satisfy a relational expression 0.4·(W)1/2<D. Satisfying this relational expression can prevent the optical fiber preform from being deformed and to have uneven diameters due to the weight thereof in the dehydrating and consolidating process in fabricating the optical fiber preform, even though it is a large-sized optical fiber preform having a diameter of 10 cm or more.