One of the chief advantages of optical fibre cables – over those made from copper – is that they are significantly smaller and lighter, so are easier to handle and install. Standard twisted-pair copper cables used for the old telephony trunk networks were enormously heavy, with typical cables measuring between 20 and 40mm in diameter and weighing almost half a tonne per kilometre. And that’s only a 100-pair cable; a 1,000-pair cable would frequently weigh more than three tonnes per kilometre.