Recently, computer controlled equipment for automobiles has made remarkable progress in terms of both performance and applicability. Hence, the requirements for data transmission, data processing or data reliability have grown severer and have made it more difficult for the conventional wiring harness to meet these requirements. For example, the installation of a large capacity CD-ROM into automobiles has made it necessary to use a transmission medium that is suitable for such equipment.Meanwhile, optical transmission technology has advanced greatly in the past several years and has become an indispensable element in the communications field. Optical components and optical fibers have been developed for automobiles, and the optical data link has come to be a transmission medium in place of the conventional wiring harness for intra-vehicle equipment communication. This paper describes an optical data link for automotive use and is described in terms of structure, specification, application and reliability. The future perspective is also discussed.