Structured Cabling for GPU Clusters: A Complete Guide
From fiber selection to MPO/MTP trunking: everything you need to know about cabling a high-density GPU cluster.
GPU clusters operate at network speeds that traditional data center cabling was never designed for. At 400GbE and 800GbE, fiber optic cabling is not optional—it is the only viable interconnect for spine-leaf fabrics connecting GPU racks.
The choice between OM4 and OM5 multimode fiber depends on the deployment. OM4 supports 400GbE at distances up to 100 meters using MPO-16 connectors. OM5 extends reach and supports wider wavelength division multiplexing for future-proofing.
MPO/MTP trunk cables are the backbone of GPU cluster networking. These high-count fiber assemblies (12, 16, or 24 fibers per connector) connect top-of-rack switches to spine switches. Proper polarity management and connector cleanliness are critical.
Within each rack, Direct Attach Copper (DAC), Active Optical Cables (AOC), and Active Electrical Cables (AEC) connect GPU nodes to top-of-rack switches. The choice depends on distance, speed requirements, and switch port compatibility.
Every connection must be tested before the cluster goes into production. OTDR testing maps the entire fiber path, while insertion loss and return loss measurements verify that each connection meets TIA-568 link budget requirements. A single marginal connection in a 5,000-connection cluster can degrade training performance across all GPUs.