GYTS [Outdoor Optical Cable for Communication with Metal Strengthening Member, Loose Sheath Strand Filling, Steel-Polyethylene Bonded Sheath] The structure of the optical cable is to insert a single-mode or multi-mode optical fiber into a high-modulus plastic and fill it with a waterproof compound. In the loose tube, the center of the cable core is a metal strength member. For some optical cables with a certain number of cores, the metal center strength member is extruded with a layer of polyethylene. The loose tube (and filling rope) is twisted around the central strength member into a compact and rounded cable core, and the gap in the cable core is filled with a water-blocking compound and an outer steel-polyethylene adhesive sheath is extruded into the cable.