GYTA/S cables are constructed with a 250μm optical fiber sleeved in a loose sleeve made of high modulus material, which is filled with a waterproof compound. At the center of the cable core is a metal reinforcement, which for some core numbers is extruded with a layer of polyethylene (PE HAWM). The loose tube (and filler) is twisted around the center reinforcement to form a compact and round core, with gaps in the core filled with a water-resistant filler. Aluminum plastic coated tape (APL) is wrapped longitudinally and then extruded into a polyethylene sheath for pipelines and overhead systems.