IBM has developed a light based processor interconnect that will allow processors to communicate between each other much faster, at lower heat than the current copper tracks used. While light has been used as a communication method for a long time, the new converter is much smaller than anything previously produced. The small size allows it to be used at board level for processor bus style applications.
While a copper atom passing an electron to another is one of the quickest chemical reactions possible, light is still about 100 times faster and produces much less heat. While the processors themselves are getting ever closer to the limit of miniaturization possible using current technology, this could drive a new way to get systems smaller, by reducing the size of the interconnect components and paths.
This also eliminates a lot of the cross talk between tracks that limits the speed that copper tracks can sustain. It will be a few years before this makes it out of the lab and into real systems, but this could change the landscape for supercomputers and compute clusters.
Since Infiniband seems to have bitten the dust, if this technology could be extended to link physically separate systems, it could help with the development of scalable clusters.