Optical fibres are housed in loose tubes that are made of high-modulus plastic and filled with tube filling compound. The tubes (and fillers) are stranded around a metallic central strength member to form a cable core. The core is armored with a layer of fire resistance tape and corrugated steel tape. Then a LSZH inner sheath is extruded and armored with another layer of fire resistance tape and corrugated steel tape. Then a LSZH middle sheath is extruded and wrapped with steel wires. Finally, a LSZH outer sheath is extruded.