800G DACs and 800G AOCs are being deployed in large numbers due to the rapidly growing bandwidth demands of modern data centers and hyperscale computing networks. Due to the high-speed interconnect requirements of AI training, cloud computing, and big data analytics, traditional 100G networks are no longer able to meet the bandwidth needs of some core applications. As an alternative to optical modules, 800G DACs, with their low cost, low latency, and ease of deployment, are becoming a key component of short-haul interconnects in high-performance data centers. This article will provide a comprehensive understanding of 800G DACs and AOCs.
800G DAC is a high-speed interconnect solution based on copper cables. It features fixed QSFP-DD 800G or OSFP 800G form factors on both ends, allowing direct connection to switches, servers, or network storage devices. Unlike traditional optical modules and fiber patch cables, DAC integrates the transmission medium and interface into a single unit, reducing cabling complexity and facilitating fault detection.
800G direct attach cable utilizes a coaxial copper cable structure with multiple conductor pairs and shielding, significantly reducing electromagnetic interference and ensuring signal integrity. In essence, an 800G DAC is like an all-in-one high-speed network cable, just plug and go, requiring no additional optical components, cleaning, or maintenance.
800G DAC transmission distances are typically under 2 meters, and are commonly used within switch racks and to connect adjacent racks. This simplifies cabling and installation.
An 800G AOC is a fiber optic cable with fixed optical modules at both ends. It integrates light-transmitting and light-emitting devices and driver chips, enabling high-speed transmission via optical signals. Unlike traditional solutions that require separate optical modules and patch cables, an AOC integrates the optical module and optical fiber, making them inseparable.
800G AOCs typically use multimode optical fiber as the transmission medium and support data rates up to 800Gbps. They typically have QSFP-DD or OSFP connectors on both ends, allowing them to be directly plugged into the corresponding ports on switches, servers, or storage devices for high-speed interconnection. Compared to copper cables, AOCs are lighter and offer lower signal attenuation, making them particularly suitable for short- to medium-distance, high-bandwidth interconnections of approximately 1-300 meters.
The main advantages of the 800G DAC are as follows:
Compared to 800G optical modules, it has lower power consumption, with passive 800G DACs consuming nearly zero power. This is highly advantageous for large-scale data center deployments, effectively reducing overall energy consumption and saving operating costs. While maintaining the same transmission speed, it meets the demands of high-bandwidth applications.
800G DAC is also more cost-effective. While 800G optical modules require expensive lasers, optics, and cabling, DACs eliminate the need for optical chips and additional cabling, making their deployment costs significantly lower than optical modules. This makes them a better choice for companies or organizations with limited budgets but high bandwidth needs.
An 800G twinax cable uses electrical signals for data transmission, eliminating the need for optical-to-electrical conversion, resulting in extremely low latency. This makes it ideal for latency-sensitive applications such as high-frequency financial trading and intelligent driving.
Finally, the integrated design of the 800G Ethernet cable makes it easier to deploy and maintain, requiring no additional configuration for plug-and-play deployment. Its physical resistance is also greater than that of optical fiber, enabling deployment in complex environments and reducing subsequent maintenance challenges.
The main advantages of 800G AOC are as follows:
The 800G active optical cable can transmit signals unaffected by electromagnetic interference. This is because it converts electrical signals into optical signals for transmission, making it suitable for environments with high electromagnetic noise.
Compared to the 800G DAC, it has a longer transmission distance, typically up to 30 meters, enabling coverage of more distant equipment, something the 800G DAC cannot achieve.
800G AOC is lighter and thinner, enabling better deployment in compact spaces without compromising rack heat dissipation.
800G DAC has a limited transmission distance, typically less than 2 meters, making it unsuitable for interconnection within a data center or even across racks. Furthermore, due to its thick cables and poor toughness, it is difficult to deploy and manage in high-density environments. Another common feature of both 800G DAC and 800G AOC is that their length cannot be flexibly adjusted; the transmission distance is fixed at the factory.
800G AOCs also have relatively high power consumption. While lower than the combination of 800G modules and patch cables, they are still higher than 800G DACs. Due to the use of electronic chips and lasers, their manufacturing costs are much higher than those of chipless DACs, resulting in higher deployment costs.
AI Cluster
AI training requires extremely high bandwidth and latency for interconnection between GPUs. With its low latency and low power consumption, 800G DACs are ideal for interconnecting GPU servers and switches within a rack. Hyperscale Data Centers
In hyperscale data centers like Facebook, Google, AWS, and Alibaba Cloud, the number of interconnections between TOR switches and servers is enormous. Deploying 800G DACs not only reduces cabling costs but also reduces power consumption and operational costs.
Storage Interconnect
In storage area networks or database clusters, data access latency directly impacts the service experience. 800G DACs ensure fast data exchange between storage and compute nodes through short-distance, low-latency interconnects, accelerating the response time of core applications such as database queries and virtualized storage access. They are ideal for I/O-sensitive storage architectures.
High-Performance Computing
In HPC scenarios, compute nodes require high-speed interconnects to form clusters to perform large-scale scientific computations, such as weather simulations, gene sequencing, and quantum chemistry simulations. 800G AOCs provide stable, high-speed optical transmission within a 30-meter range, supporting low-latency interconnection between nodes. Furthermore, their optical signal transmission is immune to electromagnetic interference, ensuring the long-term stability of HPC systems.
Leaf-Spine Architecture
Leaf-spine topology is the mainstream design in modern data centers, requiring large-scale, high-speed links between switches to carry east-west traffic. 800G AOCs not only meet high bandwidth demands but also utilize lightweight fiber cabling to avoid cabinet congestion and heat dissipation issues caused by overly thick copper cables. AOCs offer greater flexibility and efficiency when interconnecting switches across racks spanning tens of meters.
800G DAC and 800G AOC have their own advantages and application scenarios, and the choice depends on your needs. For example, if you need to connect TOR switches within a rack, an 800G DAC is a low-cost solution. If you need to connect across racks, 800G AOC is undoubtedly the better choice.
