The 250μm optical fibers are placed in a loose tube made of a high-modulus material, which is filled with a water-resistant compound. At the center of the cable core is a metal reinforcing core; for some fiber optic cables, a layer of polyethylene (PE) is extruded over this core. The loose sleeves (and filler rods) are stranded around the central reinforcing core to form a compact, circular cable core, with all gaps within the core filled with water-blocking filler. A polyethylene inner sheath is extruded after the aluminum-plastic laminated tape (APL) is longitudinally applied, followed by the extrusion of a polyethylene outer sheath after the double-sided plastic-coated steel tape (PSP) is longitudinally applied, completing the cable structure.