OPTICAL-FIBER-COMPOUNDED OVERHEAD ELECTRIC WIRE AND MANUFACTURE OF DOUBLE TUBE

PURPOSE:To provide an optical-fiber-compounded overhead electric wire which can retain air-tightness stably for a long duration and to continuously manufacture a double tube with high air-tightness and durability. CONSTITUTION:Metal elemental wires 4 having an aluminum layer on the surface are stranded on the outer circumference of a double tube 3 which includes optical fibers 2 in the inside. Regarding the resultant optical-fiber-compounded overhead electric cable 1, the double tube 3 is composed of an inner tube 5 manufactured by forming tape-like inner tube parts 7 made of an oxygen-free copper into a cylindrical shape and butting and welding the end parts of the parts and an outer tube 6 manufactured by forming tape-like outer tube parts 8 made of an aluminum material into a cylindrical shape in the way it closely cover the outer circumference of the inner tube 5.