| 摘要 |
An optical fiber cable is constituted by a cylindrical spacer having on its surface helical grooves reversing their direction at a given pitch in which a stack of ribbon optical fibers is received. In the optical fiber cable, the reverse angle phi of the groove is 210 DEG ≤ phi ≤330 DEG ; the groove has a size to contain a virtual circle therein whose diameter D is represented by equation of D = (W<2> + (N.T)<2>)<1/2> where W is the width of the ribbon optical fiber, T is the thickness of the ribbon optical fiber, and N is the number of the ribbon optical fibers stacked in a groove; the angle &thetas; formed between each of side walls of the groove and a line connecting the center of the bottom of the groove and the center of the spacer varies periodically; and the angle &thetas; of the side wall on the inner side of the curvature of the center of the groove increases continuously and monotonously at least over the part extending from a position distant from a helical portion between adjacent reverse portions at approximately 90 DEG in a circumferential direction to the next reverse portion. <IMAGE>
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