General purpose bidirectional optical backplane: high-performance bus for multiprocessor systems

We report the first bidirectional optical backplane bus for a high performance multiprocessor system operating at wavelengths of 632.8 nm and 1300 nm. The optical backplane employs an array of multiplexed holograms, in conjunction with a waveguiding plate within which cascaded fanouts are generated. Data transfer rate of 1.2 Gbit/sec at 1300 nm is demonstrated with a single bus line for a system composed of nine processor/memory boards. To provide a reliable system, packaging-related issues, such as the detector size and misalignment effects are addressed. Theoretical treatment to minimize fluctuations among the received power at each processor/memory board is further presented and an optimum design rule is provided. The backplane demonstrated here is for general-purpose. It can support standard multiprocessor buses such as Futurebus+, Multibus II, etc. It also can function as a backplane bus in existing computing systems and significantly reduce the bottlenecks that accompany electrical interconnects.