160-Channel 0.5-nanosecond Hybrid Digital Correlator Based Upon Fiber Optic Delay Lines

Abstract

In order to implement digitally the correlation function, three operations are needed: delay, multiplication and averaging. The hybrid architecture of a multichannel fiber optic digital correlator (MFODC) shown in Fig. 1 implements the delays using optical fibres and coaxial cables, the multiplication using AND gates and the averaging by repeating the measurements and collecting the data using high speed high capacity counters. The main advantage of this architecture as proposed in [1] and demonstrated in the first 8 channel 10 ns MFODC [2] is that it eliminates the clock distribution, which is a major impediment in increasing the speed of electronic correlators. Using shift registers and clock distribution, the commercially available electronic multichannel correlators have lag times no less than 5 ns.