A Method for All - Positive Optical Multilayerperceptronsi

The most promising approaches for optical neural networks are based on intensity encoding. However, a serious drawback of intensity encoding is the lack of negative values and optical subtraction, which are essential for rendering neural networks useful. To overcome the need for optical subtraction, a novel training method is described here that is especially useful for optical multilayer neural networks. In this method, subtraction is implemented as a transformation of the interconnection weights which makes possible the implementation of mul-tilayer perceptrons with optical thresholding. The method is straightforward to implement in optical neural networks where learning occurs under external electronic/computer control.