400G QSFP-DD DAC Cable: High-Speed, Low-Latency Data Center Connectivity
What Is a 400G QSFP-DD DAC Cable?
A 400G QSFP-DD (Quad Small Form-factor Pluggable Double Density) Direct Attach Copper (DAC) cable is a cost-effective, low-power interconnect solution designed for short-range, high-bandwidth data center applications. Using eight lanes of 50G PAM4 signaling, it supports up to 400Gbps over passive copper cables without the need for optical transceivers or external power.
Advantages of 400G QSFP-DD DAC Cables
✅ Ultra-Low Latency
Ideal for latency-sensitive environments like high-frequency trading, AI computing, and real-time data processing.
✅ Cost-Efficiency
Eliminates the need for optical modules and fibers, significantly reducing CAPEX for top-of-rack (ToR) and switch-to-server connectivity.
✅ Low Power Consumption
With no need for electrical-to-optical conversion, passive DACs use less than 0.1W per end—perfect for green data centers.
✅ High Reliability
Simplified architecture means fewer points of failure and improved mechanical stability over short distances (typically <2m or 3m).
Common Use Cases and Application Scenarios
| Use Case | Description |
|---|---|
| ToR Switch to Server | Ideal for connecting 400G switches to high-performance computing nodes. |
| Intra-Rack Cabling | Used within racks to link GPUs, storage, and CPUs in tightly integrated systems. |
| AI and HPC Clusters | Enables GPU-GPU low-latency communication, especially in NVIDIA-based clusters. |
| Interconnect for HFT | Ultra-low-latency interconnects for high-frequency trading platforms. |
Compatibility and Standards
The 400G QSFP-DD DAC cable is compliant with IEEE 802.3cd, QSFP-DD MSA, and SFF-8679 electrical interfaces. Optech, a trusted Taiwan TAA-compliant manufacturer, ensures full compatibility with switches from Cisco, Arista, Juniper, NVIDIA (Spectrum series), and Broadcom-based NICs.
Conclusion
400G QSFP-DD DAC cables deliver unmatched performance, reliability, and cost-efficiency for short-range data center interconnects. Whether you’re scaling AI compute clusters or upgrading your ToR infrastructure, Optech’s TAA-certified DAC cables offer a trusted solution tailored to next-gen networking.
About Optech
Optech Technology Co. Ltd was founded in 2001 in Taipei, Taiwan. The company was created with a sole purpose, to provide a wide and high quality portfolio of optical products to a very demanding and fast evolving market.
To respond to the permanent increase of IP traffic, Optech portfolio is constantly growing. Since the beginning, the company has always been up to date with the latest innovations on the market. Today, we are proud to deliver a large selection of 25G SFP28, 40G QSFP+, 100G QSFP28, 200G QSFP56, 400G QSFP-DD, 800G QSFP-DD and OSFP optical transceivers and cables.
Optech has a large portfolio of products which include optical transceivers, direct attach cables, active optical cables, loopback transceivers, media converters and fiber patch cords.
Through its large selection of optical products, that have a range of data speed from 155 Mbps to 800 Gbps and reach distances up to 120km, Optech products are suitable for various industries such as telecom, data centers as well as public and private networks.
| Optech Part Number | Length (meter) | AWG |
| OPQSDD-T-X5-PEE | 0.5 | 30 |
| OPQSDD-T-01-PEE | 1 | 30 |
| OPQSDD-T-A5-PEE | 1.5 | 30 |
| OPQSDD-T-02-PCE | 2 | 28 |
| OPQSDD-T-B5-PCE | 2.5 | 28 |
| OPQSDD-T-03-PCE | 3 | 28 |
To know more about Direct Attach Cables (DAC) click here and to know the difference with Active Optical Cable (AOC) click here.
For additional information about our 400G QSFP-DD DAC, or price inquiry, please contact us at sales@optech.com.tw
