Co-packaged optics (CPO) integrates optical components directly with networking silicon to reduce power consumption and improve signal integrity at high speeds. LinkX includes CPO solutions where silicon photonics modulators are mounted directly on the switch ICs rather than in separate pluggable transceivers.

XDR (eXtreme Data Rate) is NVIDIA’s 800G InfiniBand generation. It’s based on 200G PAM4 (pulse amplitude modulation with four levels) signaling, which encodes 2 data bits per clock pulse at approximately 100 GHz clock rate, doubling the per-lane throughput compared to NDR’s 100G PAM4.

DR4 (data center reach) supports up to 500 meters using four parallel channels over eight fibers with MPO-12/APC connectors. FR4 (far reach) supports up to two kilometers by multiplexing four channels of different laser wavelengths into a single fiber pair using Lucent connectors (LCs). The two types are not interchangeable. DR4 is parallel and FR4 is multiplexed, so they can’t be directly linked to each other.

IHS (integrated heat sink) transceivers have cooling fins built into the plug and are used exclusively in NVIDIA Quantum switches (Q3400, Q3200, and Spectrum SN56x0 Ethernet switches). RHS (riding heat sink) transceivers have a flat-top design and are used in ConnectX-8 adapters, DGX B300, and NVL GB300 compute systems. The two types are not interchangeable due to their different cooling requirements.

Both are active copper cable technologies, but they serve different roles. AECs use digital signal processors (DSPs) at each end to restore and retime signals, enabling reach up to three meters, primarily for switch-to-switch connections, consuming ~27 watts per end. LACCs use lower-power linear amplifier ICs (~4 watts) to extend signal reach up to 2.5 meters and are used for switch-to-adapter (e.g., ConnectX-8) connections.

At XDR’s 200G PAM4 signaling rates, passive DAC cables have a maximum usable length of under 0.7 meters, which is too short to be practical in most deployments. For this reason, all NVIDIA XDR copper cables are active (either LACC or AEC), which extend usable reach to 2.5–3 meters.

The 200G PAM4 XDR signal operates at a ~100 GHz clock rate, compared to ~50 GHz for NDR’s 100G PAM4. The faster signal transitions cause wires to act more like antennas, radiating signal energy off the cable. This signal degradation limits usable copper length, which is why XDR LACCs are shorter than NDR ACCs.

XDR and CPO deployments use the same MPO-12/APC single-mode crossover fiber cables as NDR/400G, meaning customers can reuse existing NDR fiber infrastructure. NVIDIA offers straight and 1:2 splitter MPO-12/APC cables in lengths from three to 150 meters. For reaches beyond 150 meters or LC-LC fiber cables, third-party suppliers such as Corning, Panduit, or CommScope should be used.

XDR DR4-based transceivers use MPO-12/APC (multiple push-on 12-fiber, angled polished connector) connectors. The angled polish reduces back-reflections that can distort data signals. Only eight of the 12 fiber positions are used: four transmit and four receive. FR4-based transceivers (2 km reach) use LC duplex connectors instead.

Yes, with some nuance. The Q3200 switch supports NDR 400G cables and transceivers for backwards compatibility with 100G PAM4 and 50G PAM4 HDR. The Q3400 switch supports only select NDR cables and transceivers. XDR transceivers cannot downshift to 100G PAM4 on their own. Backwards compatibility is handled at the switch or host channel adapter (HCA) level, not in the cables or transceivers.

No. Copper cables (DAC, LACC, and AEC) can’t be used with the Q3450 CPO switch. The CPO switch uses MMC-12/APC fiber connections only.