IEC 60794-6-20:2020 is a family specification covering optical fibre outdoor cables which are flame retardant and thus also applicable to indoor environments. These cables generally possess the characteristics associated with outdoor cable designs having similar thermal and mechanical robustness that makes them suitable for use in the outside plant, while simultaneously exhibiting the fire performance required in indoor premises. A typical application is for example the extension of a "shorter length" of an outdoor cable into the building.