Abstract: An optical fibre transmission cable has a prestressed reinforcement which has a tensile modulus of (4-6).times.10.sup.6 psi, a flex modulus of (1.0-5.7).times.10.sup.6 psi and a thermal coefficient of linear expansion of approximately 2.8.times.10.sup.-6 /.degree.F. and comprises a glass fibre roving saturated with synthetic resin material and held under tension by the synthetic resin material. The reinforcement and an optical fibre are provided within a synthetic resin material sheathing and the reinforcement provides the required mechanical reinforcement properties without introducing electrically conductive material into the cable. A method of making the reinforcement and the cable is also disclosed.