The 400G QSFP-DD DAC provides a QSFP-DD-to-QSFP-DD copper direct-attach solution and it is suitable for very short links and offer a cost-effective way to establish a 400-Gigabit link between QSFP-400G ports of switches/routers within racks and across adjacent racks. This DAC is designed with ultra-low loss materials, square rings, twisted pair cable 8 wires and shell extension construction for superior mechanical properties and bending performance. It is tested in actual switching systems to ensure optimal signal integrity and the best end-to-end performance. AICPLIGHT currently offers 400G QSFP-DD DAC in lengths of 0.5, 1, 1.5, 2, 2.5, and 3 meters, ideal for SDN, ML, and Cloud Computing.