The structure of GYTC8S optical cable is that 250μm optical fiber is sheathed in a loose tube made of high modulus material, and the loose tube is filled with waterproof compound. The center of the cable core is a metal reinforced core (also non-metallic, such as FRP, etc.), and the loose tube (and filler rope) is twisted around the central reinforced core to form a compact circular cable core. A layer of plastic-coated aluminum tape (APL) is added to the sheath outside the cable core in the form of longitudinal wrapping, and finally a polyethylene sheath is squeezed together with the steel strand to make the cross section of the “8″ shape.