JPS5654407A - Submarine optical cable - Google Patents

Abstract

PURPOSE: To prevent the breakage of optical fibers at the laying and the increase in light losses by making the twisting directions of the inner layer and outer layer of the sheath wires of a submarine optical cable mutually opposite and specifying the twisting pitch and the number of sheath wires so as to balance the torque produced.

CONSTITUTION: In the submarine cable consisting of a central support 3, an optical fiber core 4, a cushion layer 5, a copper pipe 6, a housing 7 and sheath wires 1, 1', the twisting directions of the inner layer 1, and outer layer 1' of the sheath wires are made mutually opposite and the twisting pitch P₁ of the inner layer and the pitch P₂ of the outer layer are limited to (P₁/D₁)/(P₂/D₂) ≥0.65 when the core diameter of the inner layer is defined as D₁ and the core diameter of the outer layer as D₂ in order to keep the twisting pitches of the inner and outer layers at 10W20 times the core diameters of the respective layers and cause the elongation characteristics of both to nearly coincide. The number N of wires of the respective layers is made ≤40 pieces and P₁/P₂ is kept within around 10% of the formula (E₁D₁ ²N₁d₁ ²)/(E₂D₂ ²N₂ d₂ ²). (E is Young's modulus, (d) is the effective as tensile bodies of the sheath wires, affixes 1, 2 show the inner layer and the outer layer respectively). In this way, the rotation during laying of the cable is suppressed, elongation decreased and breakage prevented.

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