Fiber optics having a liquid core, which comprises a liquid of high radiation transmission, and a sheath made from a copolymer of vinylidene fluoride which comprises at least 20% by weight and at most 75% by weight of copolymerized units of vinylidene fluoride, and copolymerized units with at least one further fluorine-containing monomer are described. Suitable further monomers are, in particular, hexafluoropropylene, or hexafluoropropylene and tetrafluoroethylene. The fiber optic can, if appropriate, be provided with pigments or other coloring additives. The sheath made from the copolymer of vinylidene fluoride has excellent adhesion to other materials and can therefore easily be bonded to other materials.