The fibers, 250µm, are positioned in a loose tube made of a high-modulus plastic. The tubes are filled with a water-resistant filling compound. The cable core is filled with the filling compound to protect it from water ingress, over which a thin PE inner sheath is applied. Tubes (and fillers) are stranded around the strength member into a compact and circular cable core.
A steel wire, sometimes sheathed with polyethene (PE) for cable with high fiber count, locates in the centre of the core as a metallic strength member.
After the PSP is longitudinally applied over the inner sheath, the cable is completed with a PE outer sheath.