Figure 5. Experimental realisation of a single layer spiking neural network.

a)The device consists of four photonic neurons, each with 15 synapses. Each synapse corresponds to a pixel in a 3x5 image (see b)) and is encoded in the wavelengths corresponding to the ring multiplexers (see numbering in b)). The full device comprises an integrated photonic circuit built up from 140 optical components. b) The change in output spike intensity is shown for the four trained patterns illustrated on the right-hand side. The neural network successfully recognizes the four patterns as each neuron only responds (spikes) to one of the patterns. The error bars denote the standard deviation for n=5.