10 GHz Optoelectronic Circuit with Variable Sigmoid Shaped Activation Function for Photonic Neural Networks

This paper introduces an opto-electronic and opto-electronic-opto circuit capable of generating a Sigmoid shaped non-linear activation function (NLAF) for photonic neural networks. The main element of the circuit is a III-V photonic integrated circuit featuring an O-band semiconductor optical amplifier (SOA) co-integrated with a uni-travelling carrier photodiode, connected to a Bi-CMOS transimpedance amplifier (TIA). Experimental results from two 10 GHz 32-level mirrored step-wise pulse sequences, and three 30-level random peak power pulse sequences, validate the proposed concept, showcasing the variation of the achieved sigmoid NLAF from nearly stepwise to linear by appropriately varying the SOA current, injection of an external CW signal and proper configuration of the TIA settings.