The invention introduces the concept of very low cost, fully integrated, large scale planar polymer light guide networks. These networks are intended primarily for automotive applications, including data communication, multiplex, sensor, switch and display networks. However, the concept is also applicable in other areas where the length of the network does not exceed a few meters. The basic idea is to `cut` a thin sheet of clear plastic (polymethylmetacrylate polycarbonate, or polystyrene) into a whole network consisting of optical links, couplers, sensors, etc. . . . In addition to being low cost, planar polymer light guide networks extend the one dimensional geometry of fiber optics into two dimensions, adding tremendous design capability and versatility.