To provide an SZ slot type optical cable in which optical loss is small by obtaining a groove locus without causing small bending ina fiber ribbon to be hused in the groove of an SZ slot.
The SZ slot consists of a tension member and a resin slot layer in which one or more spiral grooves are formed on the tension member in the SZ direction, and the spiral groove plots approximately sine wave locus. When the locus of the spiral groove is Fourier expanded, and the ratio of the second order high frequency component, the ratio of the third order high frequency component, the ratio of the fourth high frequency component are called D2, D3 and D4, respectively, and the reference value Φ0 of the reversal angle is defined as Φ0=0.068D22-4.2D3+0.18D42+275, by limiting the reversal angle Φ as ≥0.97Φ0 and ≤1.03Φ0, and restrainting the movement of the fiber ribbon housed in the spiral groove, it is possible to reduce the transmission loss by preventing the occurrence of small bending of the fiber ribbon.
YAMANAKA MASAYOSHI
OHASHI KEIJI
Iwa Saki Kokuni
Kawamata Sumio
Shunichi Takahashi
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