For fast computer-internal data transmission between different components, two new optoelectronic parallel bus systems have been developed. They are particularly appropriate for use as backplanes. The first optical backplane structure consists of a lot of circular transparent plates with a refractive index n1 and covered on both sides by a material with a refractive index of n2 (n21). The plates are optically isolated and arranged in a stack. This bus system is referred to as the optical parallel plate stack (OPPS). The optical bus signals are coupled in and out of the stack at the periphery edges of each individual plate. The second optical backplane structure consists of strips of a light-transmitting medium with, for instance, a rectangular cross section. The optical transmitting medium (refractive index n1) is cladded by a coating (refractive index n2 and n21). The strips separated by an optical isolation are put together, thus building a plate. This system is referred to as an optical parallel strip plate (OPSP). The optical signals are coupled in and out of the strips through the narrow surfaces of the strips. Study results concerning the radiated power and pulse dispersion of received optical signals show that data-transfer rates of more than 1.5 Gbit/s per plate channel and strip channel, respectively, can be realized at a bus length of 1 m.
"Two new developments for optoelectronic bus systems", Proc. SPIE 1505, Optics for Computers: Architectures and Technologies, (1 September 1991); doi: 10.1117/12.47021; https://doi.org/10.1117/12.47021