Nonlinear Optical Vector Processing at 50 Gbs using Linear Silicon Photonic Circuits

The need for high-speed, energy-efficient computing in machine learning and real-time communication necessitates innovations beyond conventional digital and analog electronics to sustain computational power advances without requiring prohibitive energy amounts. Photonics has emerged as a promising platform demonstrating significant highlights in the field of linear transformations. Adopting, however, the use of photons within a broad range of computing applications necessitates their successful employment also in nonlinear vector processing and matching functionalities, which still continue to comprise the stronghold of electronics. In this direction, we demonstrate nonlinear optical vector processing in the form of Hamming Distance (HD) calculation and Content Addressable Memory (CAM) bank operations using linear optical circuits on Silicon photonics (SiPho) at a record-high-speed of 50 Gb/s, enabling advances in pattern matching, error-correction and look-up tables. The processor employs a 4×4 crossbar architecture with 56 GHz SiGe electro-absorption modulators to compute HD between 2-bit optical vectors. It achieves error-rates of ~ 10⁻³ in CAM and ternary CAM applications that correspond to zero HD, improving state-of-the-art CAM speed performance by > 2.5x. Scalability is enhanced by employing space-wavelength multiplexing schemes via a WDM-enabled SiPho processor cell, which is experimentally demonstrated at 50 Gb/s and offers the potential to increase the computational capacity in a reduced insertion loss and power consumption envelope. The realization of HD calculation and CAM matchline operations via linear optical transformations can pave the inroad towards implementing additional nonlinear optical vector transformation processes at high data-rates via linear silicon photonic circuits, like the calculation of Euclidean distance and Cosine distance metrics.