| 摘要 |
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). Further after the additive-diffusing step, a thermal-strain-removing step is carried out to remove thermal strain by a heating treatment of a wider region R3 than heated regions R1, R2 in the fusion splice step and in the additive-diffusing step of the fusion-spliced portion A, at a temperature of not less than 500° C. nor more than 1200° C. (FIG. 1F).
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