High-bandwidth, optical-fiber delay-line multichannel digital correlator

We present an implementation of a multichannel digital correlator based on passive optical fiber delay lines capable of achieving higher real-time bandwidths than current-generation, purely electronic instruments. Theoretical limits are shown to be in the 10(3) channels and tens of gigahertz range. Digital correlation is demonstrated with instruments based on laser diodes and optoelectronic single-bit AND multipliers consisting of eight channels at a 100-MHz sample rate and four channels at 500 MHz. Low-cost optoelectronics operating at 800 nm are shown likely to be suitable for up to 1-GHz sample rates. Applications for which high bandwidth correlation is necessary or advantageous are considered, and future, more compact, and all-optical architectures are suggested.