| 摘要 |
PROBLEM TO BE SOLVED: To enable thermal protection of optical fiber and packing gel of a metallic tube by providing a thermal diffuser between an auxiliary tube for inserting optical fiber in the metallic tube and a tight closing part. SOLUTION: The thermal diffuser 15 is situated between the first auxiliary tube 10, the second auxiliary tube 12 in the metallic tube 6 situated at the place of laser torch and the tight closing part of the metallic tube 6. The thermal diffuser 15 is secured so as to oppose the closing part over capillaries 12, 13 for injecting the gel. The thermal diffuser 15 receives the energy coming from the laser torch at the part named as an impact point and disperses the same over the entire surface and throughout the thickness, which has the effect of reducing the maximum temperature at the impact point. Therefor, the maximum temperature at the impact point is kept below the threshold temperature at which hydrogen generating phenomena in the packing gel 14 are started. The optical fiber in the first auxiliary tube 10 is protected in an advantageous state. |
