| 摘要 |
PROBLEM TO BE SOLVED: To obviate the occurrence of the swallowing, protruding, etc., of optical fiber units accompanying the elongation and contraction of a cable for pneumatic feed leading-in by specifying the difference between the coefft. of linear expansion over the entire part of the cable for pneumatic feed leading-in and coefft. of linear expansion of the optical fiber units inserted into pipes for force feeding to a specific range. SOLUTION: This cable is constituted by arranging a cable body 10 obtd. by aggregating eight pieces of the pipes 11 for force feeding around an intervening member 12 and forming a wrapping layer 13 on their circumferences and a supporting wire 15 in parallel and integrating both with an integral sheath 14. The difference between the coefft. of linear expansion over the entire part of the cable for pneumatic feed leading-in and the coefft. of linear expansion of the optical fiber units inserted into the pipes 11 for force feeding is specified to 0 to 2×10<-5> / deg.C. As a result, the coefft. of linear expansion over the entire part of the cable for pneumatic feed leading-in and the coefft. of linear expansion of the optical fiber units inserted into the pipes 11 for force feeding are made nearly equal to each other and the swallowing, protruding, etc., of optical fiber units accompanying the elongation and contraction of the cable for pneumatic feed leading-in are suppressed.
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