ETU-LINK 400G QSFP-DD DAC is a type of direct attach copper cable designed to connect two 400G QSFP-DD ports. It offers a cost-effective, energy-efficient, and low-latency solution for short-distance data transmission within data centers. Additionally, it supports breakout mode, enabling the splitting of a single 400G QSFP-DD port into four 100G QSFP ports, thus providing increased flexibility in data transmission. This cable is widely used in data centers to meet high-speed and large-capacity data transmission requirements, simplifying the cabling structure and enhancing the reliability and stability of the data center.