Optical fibres in land cables do not support any tension or elongation because of their brittlenesss and the risk of loss of optical performance . Therefore , they need close protection from high tensile tension members with very little elasticity, offering at the same time enough flexibility to the cable as a whole . Moreover , no zinc coatings are allowed around optical fibres, as potential hydrogen generation through the zinc could cause fibre degeneration. Combining these requirements with excellent water blocking properties, Bekaert developed Fibercord, a steel wire strand with plastic coating, offering very cost effective tension relief of fibre optic cables .