| 摘要 |
PROBLEM TO BE SOLVED: To obviate the occurrence of excessive bending strains in the optical fibers housed in the grooves of a spacer even if a cable is bent by respectively specifying the relation between the outside diameter of the cable and the winding pitch of the grooves and the radius of curvature of the optical fibers determined by the pitch of the grooves and the diameter of a layer center diameter. SOLUTION: The cable outside diameter of the cable 1 is defined as D(mm), the winding pitch of the grooves 6 as P(mm), the layer core diameter which is the distance from the center O1 of the spacer 2 to the center O2 of the optical fibers 8 housed in the grooves 6 as A(mm) and the radius of curvature of the optical fibers 8 determined by the winding pitch P of the grooves 6 and the layer core diameter A as R(mm). At this time, the values defined above are so set that the conditions of R>=1400 and P<=40πD are both satisfied. The radius R of curvature of the optical fibers 8 in the state that the optical fibers are housed in the grooves 6 is given by R=A+(P/2π)<2> /A. As a result, the optical fibers 8 housed in the grooves of the spacer 2 are kept free from the excess bending strains even if the cable 1 is bent.
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