Colored optical fibers are placed into a loose tube made of high modulus material, which is then filled with thixotropic water-blocking gel. The center of the cable core contains a metal strength member. The loose tube(and filling rope)is twisted around the central strength member to form a circular cable core, with gaps in the cable core and between the cable core and steel strip filled with water-blocking gel. After being longitudinally wrapped with plastic-coated aluminum tape and then extruded with a polyethylene inner sheath, the cable is longitudinally wrapped with plastic-coated steel tape and then extruded with a polyethylene outer sheath. Finally, after being armored with a single round steel wire, the cable is extruded with a polyethylene outer sheath.