Abstract

We present experimental results for an optical array interconnection network using the correlation matrix-tensor multiplier (CMTM) algorithm, where the phase-encoded input array is optically convolved with a control image holding the interconnection weights. Two-dimensional arrays can be interconnected with complex gray-level weights by using binary phase-only spatial light modulators. The CMTM algorithm allows graceful accommodation of limited modulator size by trading off control image bandwidth for output signal-to-noise ratio (SNR). The correlation was performed by photorefractive four-wave mixing, and the interconnection information was stored in a single exposure of each control image. The control images were displayed with binary phase-only patterns etched into quartz. Multiple interconnection patterns were prestored as color-multiplexed volume reflection holograms in z-cut LiNbO₃. Fast reconfiguration between interconnection patterns is possible by using a wavelength tunable source, decoupling both the modulation and switching speeds from the slow photorefractive response. Experimental results confirmed theoretical predictions that the algorithm works best for densely connected networks, with a large fan-in to each output. Interconnection of up to 4096 inputs and outputs was demonstrated by using such dense interconnection patterns. An aggregate average SNR of over 200 was obtained for 1024 inputs and outputs.

© 1992 Optical Society of America