Towards a High-density Photonic Tensor Core Enabled by Intensity-modulated Microrings and Photonic Wire Bonding

Abstract

We propose a photonic processing unit for high-density analog computation using intensity-modulation-based microringmodulators (IM-MRMs). The output signal at the fixed resonance wavelength is directly intensity modulated by changing theextinction ratio (ER) of the IM-MRM. Thanks to the intensity-modulated approach, the proposed photonic processing unit isless sensitive to the inter-channel crosstalk. Simulation results reveal that the proposed design offers a maximum of 17-foldincrease in wavelength channel density compared to its wavelength-modulated counterpart. Therefore, a photonic tensor coreof size 512 × 512 can be realized by current foundry lines. A convolutional neural network (CNN) simulator with 6-bit precisionis built for handwritten digit recognition task using the proposed modulator. Simulation results show an overall accuracy of 96.76%, when the wavelength channel spacing suffers a 3-dB power penalty. To experimentally validate the system, 1000 dotproduct operations are carried out with a 4-bit signed system on a co-packaged photonic chip, where optical and electrical I/Osare realized using photonic and electrical wire bonding techniques. Study of the measurement results show a mean squarederror (MSE) of 3.09 × 10^−3 for dot product calculations. The proposed IM-MRM, therefore, renders the crosstalk issue tractableand provides a solution for the development of large-scale optical information processing systems with multiple wavelengths.