| 摘要 |
PURPOSE:To decrease production stages by extrusion coating a plastic covering on an optical fiber assemblage. CONSTITUTION:A cable is formed of a central support 1, optical fiber cores 2, retaining tapes 3, and a plastic covering layer 9. When the cable is applied with water pressure P, the water pressure is born by the layer 9, and the stress to be exerted upon the fiber strands is <=1/100 the water pressure, thus the fiber strands are protected against the water pressure. When the circumferential stress sigma (A) to be applied at the point A exceeds the value higher than the stress at which the layer 9 buckles, the covering layer can no longer provide protection. If tn is defined as the thickness of the layer 9 and ru as the outside radius of the cable and if these are set at Rn=tn/ru,the layer 9 buckles when the sigma (A) attains equal to the stress sigma at which said layer buckles; therefore, the relation between the size and water pressure resistance Ps of the cable is obtained by determining the relation between P and Rn at sigma (A)=sigma3. Since the max. water distance of a relaying transmission system is 1,500m(Ps=150kg/cm<3>), Rn>=0.18 and sigmas>3kg/mm.<2> are required to satisfy water pressure resistance. |
