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This paper investigates the advantages of 3D-integrated photonic interconnects for enhancing inference prefill in Mixture-of-Experts (MoE) models, focusing on the trade-offs between throughput and context window size. By simulating various MoE models with context lengths ranging from 1K to 1M tokens, the authors demonstrate significant latency reductions in high-batch scenarios and communication-limited settings when utilizing photonic systems compared to traditional copper-based GPU architectures. The findings reveal that photonic interconnects can achieve up to 5.8x improvements in performance, facilitating the necessary scale for complex AI workloads.
Photonic interconnects can deliver up to 5.8x latency improvements for large-scale AI inference, revolutionizing how we handle complex models.
With the rise of inference as today's dominant AI workload, the industry is transitioning to high-bandwidth photonic interconnects to meet the large scale-up requirements of increasingly complex Mixture-of-Experts (MoE) models. This paper quantifies the benefits of 3D-integrated photonic interconnects for inference prefill by analyzing tradeoffs between high-concurrency throughput for Large Language Model (LLM) chat and the large context windows typically required for reasoning and agentic AI. We simulate three MoE models: short context (1K--8K tokens), medium context (128K tokens), and long context (1M tokens). We evaluate this workload across existing copper-based GPU systems and one with high bandwidth integrated photonics. We show 2.1--3.2x latency improvements in the stressed high-batch regimes and 2.8--5.8x improvements over baselines in communication-limited configurations. 3D photonics enable the 1152-GPU footprint required to lower time-to-first-token, yielding 2.2--4.5x speedups across production-grade platforms when electrical systems cross their inherent scale-up-pod limits.