The present technology relates generally to fibre optic cables their manufacture and uses in the field of optical measurements including biochemical laboratory instrumentation for measuring properties of samples on microtitration plates and corresponding sample supports. The technology has also applications in various laser technologies. A fibre optic cable has an active surface with a determined form provided at a first optical interface at the first end of the cable. The first end of the cable is fused into an exemplary circular form, the fused cable end including fibre ends both within the active surface and outside the active surface. At the opposite, second end of the cable, those fibres which have their first ends at the determined active surface area, are used for forming a second optical interface. It is possible to have high transmission efficiency in optical interfaces where other than circular cross section of the light beam exists.