Abstract: Two optical fibers 10, 20 to be spliced are prepared (FIG. 1A), coatings of resin 12, 22 are removed from end portions of the respective optical fibers 10, 20 to expose glass fibers 11, 21 (FIG. 1B), the glass fibers 11, 21 are aligned each other (FIG. 1C), and a fusion step is carried out to heat the end faces of the glass fibers 11, 21 to cause fusion thereof to form a fusion-spliced portion A (FIG. 1D). After that, an additive-diffusing step is carried out to diffuse an additive added in the glass fibers 11, 21 around the fusion-spliced portion A, by a heating treatment around the fusion-spliced portion A at a first temperature of not less than 800° C. nor more than 1500° C. (FIG. 1E).

Abstract: Two optical fibers 10, 20 to be spliced are prepared (FIG. 1A), coatings of resin 12, 22 are removed from end portions of the respective optical fibers 10, 20 to expose glass fibers 11, 21 (FIG. 1B), the glass fibers 11, 21 are aligned each other (FIG. 1C), and a fusion step is carried out to heat the end faces of the glass fibers 11, 21 to cause fusion thereof to form a fusion-spliced portion A (FIG. 1D). After that, a thermal-strain-removing step is carried out to remove thermal strain by a heating treatment of a wider region R2 than a heated region R1 of the fusion-spliced portion A, at a temperature of not less than 500° C. nor more than 1500° C. (FIG. 1E).

Abstract: A process for producing a porous glass preform for optical fiber by depositing fine glass particles on an outer surface of a glass material while moving the glass material, including the steps of: preheating a portion of the glass material for not less than 5 minutes to clean the portion of the glass material in an apparatus for depositing fine glass particles; and depositing fine glass particles on the portion of the glass material cleaned by the preheating, in the apparatus for depositing fine glass particles.

Abstract: An apparatus includes a first waveguide having a first surface having a first hole through which a fiber passes, and a second surface having a second hole through which an object passes and opposing the first surface, a magic tee connected to the first waveguide, and an adjustable short plunger connected to the magic tee.