NVIDIA InfiniBand NDR (Next Data Rate) at 400 Gbps per port represents the current performance frontier for AI training cluster interconnects. Selecting the right cable type, length, and vendor for your NDR fabric is a critical infrastructure decision.
NDR 400G Port Overview
NDR delivers 400 Gbps full-duplex per port using OSFP form factor modules, with 4 electrical lanes at 100 Gbps per lane (PAM4 at 56.25 GBaud). Interconnect options:
- Passive Copper DAC: 0.5–2m, lowest latency, no active components
- Active Copper Cable (ACC): 2–5m, uses signal retiming ICs
- Active Optical Cable (AOC): 3–100m, VCSEL or EML lasers, EMI immune
- Optical Transceiver + MPO fiber: Flexible approach for longer reaches
Selecting by Distance
≤2m: Passive DAC — lowest cost, zero latency penalty. ATL Optics NDR passive DAC available in 0.5m, 1m, 1.5m, and 2m.
3–5m: Active copper cable (ACC). Signal retiming adds ~1–5 ns latency per direction.
5–30m: Active optical cable (AOC). EMI immunity, lower weight than copper.
>30m: Transceiver + structured fiber. NDR 400G SR4 reaches 100m on OM4, 150m on OM5.
Compatibility
- All NDR cables must present valid OSFP CMIS 5.0 EEPROM data — NVIDIA switches perform strict validation
- Verify cable firmware compatibility with your QM9700/QM9790 switch firmware version
- ATL Optics NDR assemblies are validated for QM9700/QM9790 and ConnectX-7/BlueField-3
Request a quote with your required length, quantity, and target platform.