The Furukawa Electric Co., Ltd.

Masahiro Yabe

Yoshihiro Arashitani

Minoru Kasahara

Kouji Mochiduki

The present invention satisfies at least one of the condition of the degree of freedom of a primary layershown in the equation (I) and the condition of the rigidity of a secondary layershown in the equation (II). Thus, a coated optical fibercapable of suppressing transmission loss in a low temperature environment is provided, in which, even when an optical fiberhaving a large effective core cross-sectional area Aof the optical fiberat a wavelength of 1550 nm and having high microbend sensitivity is used, transmission loss in a low temperature environment can be suppressed.[Math. 1]β<600  (I)()×()≤1000  (II)

Coated optical fiber, optical fiber cable, and coated optical fiber ribbon

Provided is a coated optical fiber and an optical fiber cable capable of suppressing transmission loss (microbend loss) even in an optical fiber having high microbend sensitivity. In the present invention, the degree of freedom of a primary layerrepresented by the equation (I) and the rigidity of a secondary layerrepresented by the equation (II) are set in specific ranges, respectively. Thus, the present invention provides a coated optical fibercapable of suppressing the transmission loss even when an optical fiberhaving high microbend sensitivity such as a BI fiber having a large effective core cross-sectional area Aof an optical fiber is used. The present invention can be widely used as a coated optical fiberconstituting a coated optical fiber ribbon or as a coated optical fiberhoused in an optical fiber cable. Further, an optical fiber cable including such coated optical fibersenjoys the effect of the above-described coated optical fiber[Math. 1]&#x3b2;&#x2265;600&#x2003;&#x2003;(I)()&#xd7;()&#x2264;1,000&#x2003;&#x2003;(II)

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Tokyo, Japan

Masahiro Yabe