ASTRA: A Stochastic Transformer Neural Network Accelerator with Silicon Photonics

Transformers have emerged as a dominant architecture in deep learning, demonstrating unparalleled success across a wide range of applications, including natural language processing (NLP), computer vision (CV), and scientific computing. By leveraging the self-attention mechanism, transformers achieve superior performance over traditional models such as recurrent neural networks (RNNs) and convolutional neural networks (CNNs). However, these performance gains come at a cost—high computational complexity and substantial memory requirements, making transformers particularly challenging to deploy efficiently on conventional hardware. To address the increasingly intensive computational demands of attention-based transformers, there is growing interest in developing efficient and high-speed hardware accelerators. Silicon photonics has emerged as a promising alternative to digital electronics, offering high-bandwidth and low-latency computation while improving overall computational and energy efficiency. This work introduces ASTRA, the first optical hardware accelerator that leverages stochastic computing principles for transformer neural networks. ASTRA incorporates novel full-range optical stochastic multipliers and stochastic-analog compute-capable optical-to-electrical transducer units to efficiently handle both static and dynamic tensor computations in attention-based models. Through detailed performance analysis, we demonstrate that ASTRA achieves at least 7.6 × speedup and 1.3 × lower energy consumption compared to state-of-the-art transformer accelerators.