P-DAC: Power-Efficient Photonic Accelerators for LLM Inference

As traditional electronic hardware encounters the limitations of Moore’s Law, optical computing is emerging as a promising alternative, delivering high data transmission rates, especially beneficial for big data and AI applications. Photonic accelerators, such as the LighteningTransformer, utilize optical analog signals to accelerate Transformerbased models, achieving exceptional speed and low energy consumption. However, controlling modern optical intensity modulators (e.g., MachZehnder Modulators) requires using electrical analog signals (e.g., voltage values) to adjust the optical signal intensity for realizing optical-based vector inner product calculations. Managing this modulation consumes significant power, as it involves selecting optimal electrical values through an electrical controller and converting digital signals to analog using digital-to-analog converters (DACs). In this work, we introduce P-DAC, a solution designed to reduce DAC power consumption, significantly enhancing the energy efficiency of optical accelerators for Transformer models.