NVIDIA Cable Management Guidelines and FAQ
You can download a PDF version of the full guide here.
High-speed interconnects are playing an increasingly more important role in data centers.
This note provides:
- An introduction to the terminology related to high-speed copper and optical cables and transceivers in general
- An introduction to NVIDIA's interconnect product families
- Recommendations for cables and transceivers installation
Data centers often use several different types of high-speed interconnects matching each interconnect type to specific requirements. Modern, high-speed data centers have focused on the following interconnects:
DACs (Direct Attach Copper) is the lowest cost, but after 2-5 meters (rate dependent) the attenuation of the signal is significant and becomes unrecognizable at the receiver.
AOCs (Active Optical Cable) are used from 3 meters to about 100 meters. It is not practical to install AOCs that are longer than 100 meters due to the trouble replacing them in case of issues.
Multi-mode Optics: More expensive SR (Short Range), SR4 (Short Range 4 Channels) multi-mode transceivers can be used up to 100 meters after which the signal degrades due to dispersion = the light bouncing around inside the large core multi-mode fiber and the signal pulse becoming too distorted to recognize at the receiver.
Single-mode Optics: Parallel single-mode transceivers (PSM4) are used up to 500 m. After 500 meters the cost of 8 fibers adds up with each meter, so multiplexing the four channels signals into one single fiber is more economical using CWDM (Coarse Wavelength Division Multiplexing)/FR up to 2 km and LR (Long Reach, 10 km), ER (20 km) or ZR (80 km).
Figure 1 – Different types of interconnects
8-channel devices are being added to the portfolio for 400G and 800G links on DACs, AOCs and transceivers.