109 describes cable construction and provides guidance for the use of optical/metallic hybrid cables, which contains both optical fibres and metallic wires for telecommunication and/or power feeding. Technical requirements may differ according to the. Recommendation ITU-T L. The International Electrotechnical Commission (IEC) publishes globally adopted standards that define how cables are designed, tested, and installed. They define a minimum baseline of quality and workmanshi for installing electrical products and systems.