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Relationship between optical modules and GPUs

Fiber and communications infrastructure knowledge brief Published 05 Oct 2025

Prepared for preliminary research by the ROGER FIBRE knowledge desk. Confirm optical interfaces, port or core capacity, electrical input and output, enclosure protection, thermal design and installation limits against current standards and product documentation.

NVIDIA GPUs use high-speed optical modules, including 400G, 800G, and 1. 6T transceivers, to enable multi-terabit-per-second connectivity between GPUs, servers, and storage in AI and HPC systems.

Types and Speeds

Optical modules for GPUs are designed to handle extremely high bandwidth requirements. Common types include: 400G Optical Modules: Support up to 400 Gbps, widely used for AI inferencing, mid-range model training, and connecting DGX systems to servers and storage. 800G Optical Modules: Deliver up to 800 Gbps, suitable for large-scale AI model training, real-time simulations, and massive data analytics.

1. 6T Modules: Emerging high-capacity modules for hyperscale GPU clusters, enabling ultra-fast interconnects across racks. These modules are available in QSFP, QSFP-DD, OSFP, and SFP form factors, supporting both NRZ and PAM4 modulation for multi-mode and single-mode fiber connections.

Applications in GPU Systems

Optical modules are critical for: Data Center Interconnects: Linking GPUs across racks and pods to maintain low latency and high throughput.

AI and HP

C Workloads: Enabling fast communication for deep learning, transformer models, and scientific simulations. Storage Networks: Connecting GPU-based systems to high-speed storage fabrics for efficient data transfer. In NVIDIA's ecosystem, optical modules are used in DGX SuperPODs, NVLink clusters, and AI supercomputers, ensuring seamless communication between multiple GPUs and nodes.

Emerging Technologies

Recent innovations include co-packaged optics (CPO) and on-package optical interconnects, which integrate photonic modulators directly onto GPU or switch substrates. This reduces energy consumption, increases bandwidth, and extends communication distances up to 2 km using microring resonators and wavelength-division multiplexing. Startups like Ayar Labs are implementing optical chiplets that interface with GPUs via the UCIe protocol, achieving up to 8 Tbps per GPU pair.

Deployment Considerations

The number of optical modules per GPU depends on: GPU Bandwidth: H100 GPUs with 900 GB/s NVLink require multiple optical links for inter-rack scaling. Cluster Size: Small clusters (8–16 GPUs) may need 16–32 modules, while hyperscale clusters with hundreds of GPUs may require thousands. Redundancy and Reliability: Data centers often deploy redundant links to maintain low latency and fault tolerance, effectively doubling module requirements.

Optical modules are therefore a key enabler for scaling GPU-based AI and HPC systems, providing the high-speed, low-latency connectivity that traditional copper interconnects cannot achieve.

Relationship between optical modules and GPUs - ROGER FIBRE ATELIER [PDF]

Relationship between optical modules and GPUs

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Technical note

This reference is intended for preliminary fiber and communications infrastructure research. Optical interface, fiber type, port or core capacity, electrical input and output, enclosure protection, cooling, installation limits and applicable standards must be verified for the specific project.

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