Sorting with optical compare-and-exchange modules.

Sorting is central to the solution of many knowledge-based and switching problems in advanced computation and communication systems. Parallel-pipelined sorting algorithms are appropriate for applications that demand high throughput, low delay, and many data channels. One such algorithm, the bitonic sort, can be implemented with passive perfect shuffle interconnects between active stages of compare-and-exchange (C&E) elements. In this paper we focus on optical hardware to implement the C&E operation and show that, by taking advantage of a distinctive feature of optical logic, namely, bistability, comparison circuits of remarkable simplicity are attainable. We describe implementations of C&E in a variety of optical device technologies capable of performing latching and nonlatching logic. Based on the device characteristics we outline potential application areas for each technology.