Abstract

We have previously designed a freespace optoelectronic neural system¹ based on the D-STOP architecture.² The neural architecture minimizes the number of required light transmitters and provides full connectivity between neurons, flexible functionality neurons and synapses, low signal timing skew, and accurate electronic fan-in with dendritic processing capability. Neural signals are encoded by using a combination of pulse-width modulating optical neurons and pulse-amplitude modulating electronic synapses. The neural system prototype consists of a 16-node input layer, a four-neuron hidden layer, and a single neuron output layer. The input layer consists of a 4 × 4 array of PLZT modulators. An 8 × 8 synapse scalable prototype of the neural chip and the space-invariant optical interconnection system have been fabricated. The image of the modulator array is distributed optically to the 64 synapses of the four hidden layer neurons, which are electrically connected to the output neuron. One differencing dendrite per four synapses is used. Measured synapse and dendrite unit characteristics exhibit high linearity with low power consumption. Test results allow a 100 ns minimum pulse width for neural outputs.

© 1992 Optical Society of America