Do parallel computers really need optical interconnection networks?

Several recent architectural trends appear to require some of the special properties of optical interconnection networks. The memory hierarchy will probably get deeper and the hardware will be more dynamic. Reconfigurable hardware and software are the subject of intense research. It is likely that the basic word size and the number of communication streams will be dynamically configurable. Optical interconnection networks, and in particular bit parallel free-space implementations, may provide the necessary flexibility.