First experimental demonstration of highly scalable and reconfigurable optical convolution computing based on wavelength routing

A highly scalable and reconfigurable optical convolution paradigm based on wavelength routing is proposed, which leverages the unique sliding property of an arrayed waveguide grating router (AWGR) to execute the sliding window operation of convolution in the wavelength-space domains. By directly loading two input vectors onto two modulator arrays, the convolution result is instantaneously generated at a photodetector array at the speed of light propagation. This enables the entire convolution computation to be executed within one clock cycle, eliminating the necessity for preprocessing or decomposition into elementary MAC operations. The proposed optical convolution unit (OCU) has striking advantages of high scalability, high speed, and processing simplicity compared to those based on optical matrix-vector multipliers (MVM). A proof-of-concept experiment employing standalone optical components is devised to validate optical convolution computing principles with one-bit accuracy. The classification of ten handwritten digit classes sourced from the MNIST database is experimentally demonstrated, achieving a precision of 4-bit. New algorithms for data splitting and reorganization were concurrently introduced to facilitate the convolution calculation of two-dimensional image data. Notably, through Field-Programmable Gate Array (FPGA) across varying data transmission speeds of 1MHz, 5MHz, and 10MHz, inference accuracy rates of 97.32%, 96.25%, and 94.50% were respectively achieved, demonstrating the robustness and versatility of the proposed paradigm.