Authority Guide
Choosing the right interconnect is not only a speed decision. At 400G, 800G, and 1.6T, the cable path, switch platform, port density, power budget, thermal design, connector type, and migration plan all affect whether the deployment works in production.
Start with the actual routed cable distance, then validate platform compatibility, power, airflow, cable density, and future 1.6T requirements before the BOM is locked.
For broader planning across optics, cables, AI infrastructure, validation, procurement, and OEM-compatible networking, visit the Data Center Networking Resource Center. For AI fabric planning across GPU clusters, Ethernet, InfiniBand, optics, cables, validation, and lifecycle requirements, start with the AI Networking Infrastructure Guide.
Short Answer
Use distance to narrow the interconnect family, then validate platform fit, power draw, cooling impact, cable density, diagnostics, deployment timing, and migration path. Passive DAC fits the shortest intra-rack links. ACC, AEC, and AOC support longer or denser paths. Pluggable optics and single-mode fiber support longer reach, spine layers, and 1.6T planning.
High-speed interconnect selection should follow a structured review process. The right answer depends on more than whether a cable or optic supports the target speed.
01
Use the actual rack path, service loop, bend radius, tray path, and maintenance access, not straight-line distance.
02
Validate switch, NIC, OSFP or QSFP-DD form factor, IHS or RHS requirements, coding, and supported cable or optic options.
03
Compare power draw, faceplate density, airflow, neighboring module heat, rack cooling, and cable tray fill.
04
Identify which links support 400G, 800G, and future 1.6T requirements without forcing unnecessary recabling.
Measure the actual routed path, not the straight-line distance. Include service loops, rack routing, bend radius, and maintenance access before selecting the interconnect type.
0 to 2m
Best fit for intra-rack links where low power, low cost, and short reach matter most.
2 to 5m
Useful for near-rack copper paths where passive DAC margin starts to tighten.
3 to 7m
Active electrical cable with signal regeneration for dense adjacent-rack 800G links.
10 to 100m
Optical reach for cross-row and hall-level paths where copper weight and airflow become limiting factors.
100m+
Pluggable optics and single-mode fiber for longer paths, campus links, and 1.6T planning.
Planning note: Distance narrows the options. Platform compatibility, port density, power draw, cooling impact, cable tray fill, and migration plans should confirm the final selection.
Use this table as a first-pass planning framework before platform validation, lab testing, and final BOM approval.
| Interconnect Type | Best Fit | Planning Concern | Validation Focus |
|---|---|---|---|
| Passive DAC | Shortest intra-rack links | Reach limit, cable thickness, airflow, bend radius | Port support, length, routing, link stability |
| ACC / LACC | Short copper paths where passive DAC margin tightens | Power draw, signal conditioning, platform support | Electrical behavior, recognition, link stability |
| AEC | Adjacent-rack dense 800G links | Active electronics, power, thermals, cable management | Signal regeneration, platform behavior, diagnostics |
| AOC | Cross-row links and simplified optical deployment | Integrated cable/optic replacement, length planning | Reach, platform compatibility, traffic stability |
| Pluggable optics | Longer links, spine layers, campus paths, 1.6T planning | Power, thermals, link budget, connector type, fiber plant | Optical power, FEC, DOM/DDM, traffic soak, thermals |
Dense AI networks often use different interconnect types at each layer. Short compute-to-leaf paths may use DAC. Leaf-to-spine links often move to AEC or AOC. Longer spine and super-spine paths typically use pluggable optics over single-mode fiber.
Core
DR8 / FR4 + single-mode fiber
Longer super-spine and data center paths.
Spine
AEC or AOC
Common fit for adjacent rack and dense 800G fabric links.
Leaf / ToR
Passive DAC
Short intra-rack connectivity where distance and routing support it.
Compute
GPU systems and endpoints
Validate cable timing, port count, and installation sequence before systems arrive.
Before approving a high-speed interconnect BOM, review the physical path, switch platform, power budget, and future migration requirements.
Many 800G deployment problems start as small interconnect assumptions. Review these issues before hardware reaches the rack.
Mistake 1
OSFP IHS and RHS are physically different. Confirm switch and NIC requirements before ordering modules, optics, or breakout cables.
Mistake 2
800G passive DAC reach is shorter than many 400G designs. Use ACC, AEC, or optical options when the path exceeds the passive DAC limit.
Mistake 3
Thick DAC bundles restrict airflow in high-density racks. Calculate tray fill and airflow impact before finalizing the cable type.
Mistake 4
MPO-12, MPO-16, UPC, and APC are not interchangeable. Connector mismatch creates attenuation, instability, or link failure.
Mistake 5
A fully populated 800G switch with optics adds power and cooling demand. Validate facility and platform budgets early.
Mistake 6
Optical infrastructure should be ready before GPU systems arrive. Late cabling creates idle hardware and rushed troubleshooting.
Practical takeaway: Cables are a small part of the cluster budget, but they often determine whether the larger deployment turns up on schedule.
Interconnect cost includes more than the purchase price per link. Power draw, cooling impact, reliability, spares, deployment timing, and troubleshooting risk should be reviewed together.
At high port density, cable thickness affects airflow, routing, bend radius, and service access. DAC bundles can create airflow restrictions in dense racks if tray fill is not reviewed early.
Some infrastructure carries forward better than others. Fiber paths are better suited for long-term planning, while copper cable assemblies are more generation-specific.
Practical takeaway: Use structured single-mode fiber for links expected to last more than one generation. Budget copper replacement as part of 1.6T planning.
Start with the actual routed cable distance, then validate platform compatibility, power draw, cooling impact, cable density, connector type, diagnostics, and migration path. Passive DAC fits the shortest links. ACC, AEC, and AOC support longer or denser links. Pluggable optics support longer reach and future-ready fiber paths.
Routed distance includes cable tray path, service loops, bend radius, rack routing, and maintenance access. Straight-line distance often underestimates the real cable length required for a clean and serviceable deployment.
Common issues include ordering the wrong OSFP module style, using passive DAC beyond its practical reach, ignoring cable diameter, mixing connector types, under-budgeting optic power, and ordering cable infrastructure too late.
Cable diameter affects tray fill, airflow, bend radius, routing, and service access. Thick DAC bundles can restrict airflow and make high-density racks harder to operate or expand.
Teams should use structured single-mode fiber for long-life links, treat DAC, ACC, and AEC assemblies as generation-specific, and include copper replacement in the 1.6T migration budget.
Talk to Axiom
Send Axiom your switch platform, target speed, form factor requirements, cable paths, rack layout, port count, and deployment timeline. Axiom's networking team will help review interconnect options, platform compatibility, power and cooling requirements, and 800G to 1.6T migration needs before deployment.
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