Three-dimensional waveguide interconnects for scalable integration of photonic neural networks

Johnny Moughames,Xavier Porte,Laurent Larger,Muamer Kadic,Gwenn Ulliac,Michael Thiel,Daniel Brunner,Maxime Jacquot

doi:10.1364/optica.388205

Abstract

Photonic waveguides are prime candidates for integrated and parallel photonic interconnects. Such interconnects correspond to large-scale vector matrix products, which are at the heart of neural network computation. However, parallel interconnect circuits realized in two dimensions, for example, by lithography, are strongly limited in size due to disadvantageous scaling. We use three-dimensional (3D) printed photonic waveguides to overcome this limitation. 3D optical couplers with fractal topology efficiently connect large numbers of input and output channels, and we show that the substrate’s area and height scale linearly. Going beyond simple couplers, we introduce functional circuits for discrete spatial filters identical to those used in deep convolutional neural networks.

Highlights

The interconnection of numerous input and output channels (IO-channels) is the basic operation behind many applications
We demonstrate the integration of such photonic interconnects in 3D for the first time
We successfully demonstrated complex and large-scale 3D photonic interconnects

Summary

INTRODUCTION

The interconnection of numerous input and output channels (IO-channels) is the basic operation behind many applications. A parallel and energy-efficient interconnect has been a desired technology for decades [1,2], finding use in diverse fields such as telecommunication, inter- and intra-chip data buses, and potentially bio-photonics [3] Most timely, it is highly desired for connecting layers of deep neural networks (NNs) to efficiently provide the typically large-scale vector matrix products [4]. It is highly desired for connecting layers of deep neural networks (NNs) to efficiently provide the typically large-scale vector matrix products [4] The integration of such an apparatus is challenging. Serial routing is naturally not an option, and a large number of direct physical links connecting the IO-channels is required Such channel multiplexing can be created in different dimensions, for example, in wavelength or space, and here we address spatial multiplexing. Our concept is based on mature fabrication technology, which has been exploited for photonic wirebonding between chips [16,17]

SCALING OF INTERCONNECTS

Fractal Topology for Fully Connected Layers

Haar Filters

DISCUSSION AND CONCLUSION