Title: Communicating with Low-Diffraction Lasers and Mirrors

Authors: Richard Beigel

Abstract: Optical interconnection networks, in which each processor contains a set of lasers for communication with other processors, have long been studied. In the ``regular optics'' model of Murdocca a bounded number of planar mirrors are used to redirect light beams, and each processor has a bounded number of lasers directed at a fixed set of angles, independent of the processor.

It is theoretically interesting to ignore diffraction, and assume that lasers beams travel in a straight line. In the regular optical model, we present elegant layouts for processor networks including the shuffle, grids, and Margulis' expander graph. We also disprove the existence of a certain kind of 3-dimensional layout for shuffles.

Using slightly more complicated optical devices, such as beam splitters, we design a ``light guide,'' which allows simultaneous broadcasts, subject only to the limitations of light sensors. In particular, the light guide can perform single broadcasts. Given accurate enough clocks, it can perform arbitrary permutations.

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