| 摘要 |
PURPOSE:To eliminate communication trouble without causing tensile force nor compressive force to work by mounting a clamp material on the tension member of an optical unit and engaging it with a guide member movably in the axial direction of the optical unit. CONSTITUTION:A connecting box 10 for a metallic strand wire containing an optical fiber is constituted by fitting the clamp member 12 to the lower end part of the tension member 3. One end part of a tension coil spring 13 is fixed to the bottom surface of the fixation part 12a of the member 12 and the other end part of this spring 13 is fixed to the bottom wall part 10b of the box body 10. When a metallic element wire 6 and a metallic pipe 2 extend, the optical unit 5 is drawn out of the box body 10 by length corresponding to the extension, so no tensile force works on the optical unit 5 to improve the breakage life of the optical fiber 4 and also prevent the fiber from being broken. When they contract, on the other hand, the optical unit 5 is put back into the box body 10 by length corresponding to the contraction, so no compressive force works on the optical unit 5 and the optical fiber 4 causes no microbend, thereby holding transmission characteristics excellent.
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