Optical data links and bus systems are becoming increasingly attractive for automobiles. In 1998, a first optical data bus system, based on polymer optical fibers and visible light-emitting diodes was introduced in Mercedes-Benz cars to interconnect information and entertainment devices within the passenger compartment. Since 2002, media-oriented system transport (MOST) is the standard for an optical infotainment data bus system in the automotive industry. However, with increasing demands on network flexibility, robustness, safety-relevant functions, and data rate, the currently used technologies reach their limit. A new physical layer, based on 200-μm polymer-cladded silica fibers and infrared-emitting vertical-cavity surface-emitting lasers, is a promising solution. This paper provides an overview about the state-of-the-art physical layer of standard MOST data bus systems, shows its limitations, and presents new optical-physical-layer concepts for next-generation data bus systems in cars.