Core Viewpoint - The article discusses the different types of cables used in data centers, particularly focusing on Active Optical Cables (AOC) and their advantages over traditional copper cables, as well as the specific cable choices made in the GB200 architecture. Group 1: Active Optical Cables (AOC) - AOC is defined as a cable technology that uses optical fibers between connectors while maintaining compatibility with standard electrical interfaces, enhancing speed and transmission distance [2][10] - AOC components consist of four functional parts, including high-density connectors and embedded optical transceivers for optical-electrical and electrical-optical conversion [4][5] - AOC offers various types, such as 10G SFP AOC, 25G SFP28 AOC, and 100G QSFP28 AOC, catering to different data rates [8] - The advantages of AOC include longer transmission distances, higher bandwidth, lower electromagnetic interference, and reduced size and weight compared to copper cables [11][12] Group 2: Copper Cables - Direct-Attached Cables (DAC) are copper cables designed for direct connections between devices, available in both passive and active types [17] - Passive DACs are cost-effective and consume little power, making them suitable for short-distance connections, but have limited transmission distances [20][21] - The drawbacks of passive copper cables include limited transmission distance (typically under 7 meters), bulkiness, and sensitivity to electromagnetic interference [21][24] Group 3: GB200 Architecture - In the NVL72 interconnect scheme, NVIDIA opted for 5,184 copper cables instead of optical ones, which are more cost-effective and reliable [36] - Each GPU in the NVL72 has a unidirectional bandwidth of 900GB/s, requiring 72 differential pairs for bidirectional transmission, leading to the total of 5,184 cables [36] - The GB200 architecture utilizes optical connections for GPU-GPU inter-rack communication due to the distance limitations of copper cables, while copper cables are used for cost savings in certain deployments [38]