What are the Advantages of Active Optical Cable (AOC) Compared to Direct Attach Cable (DAC) Solutions?

In the world of optical networks and Datacenters, speed and stability is everything. Many manufacturers are constantly trying to offer the best and fastest solutions for Datacenter’s interconnects so that the end-customers can receive the best possible Internet connection. In the world of optical cables the main participants on the battlefield are Direct Attach Cables and Active Optical Cables. These cables are mainly used to transfer data between servers, storages and switches in a Datacenter environment. Both solutions provide some advantages and disadvantages compared to each other.

Direct Attach Cables are copper based cables that use the same port as optical transceivers, however due to them being copper based, they offer higher cost and power savings compared to Active Optical Cables when deployed in short range applications. These cables are terminated with a transceiver-style connectors, generally SFP+ (Small Form-Factor Pluggable) and QSFP+ (Quad Small Form-Factor Pluggable). They can support Ethernet, InfiniBand or fiber channel. These cables come in two versions: Direct Attach Passive Copper Cables and Direct Attach Active Copper Cables.

Figure 1:
SC253501KXM26- BlueLAN© 40GBASE-CR4 QSFP to 4x10GBASE-CR SFP+ Direct Attach Breakout Cable (passive), 4 to 5 Meter, AWG 26

Direct Attach Passive Copper Cables (figure 1) have the capability of reaching up to 10 meters at 10 GB/s or 40 GB/s at low power. This is mainly because they have no active circuitry components.

Direct Attach Active Copper Cables (figure 2) are designed and manufactured in the same way as the Direct Attach Passive Copper Cables, however because they incorporate an active circuitry component, which boosts the power of the                                                                                                 signal, they can reach up to 15 meters 10 GB/s or 40 GB/s.


Figure 2:
SC353502JXM24- BlueLAN© 10G SFP+ Direct Attach Cable (active), 1 to 15 Meter, AWG 24

The Direct Attach Cables are most commonly used in the EDA or Equipment Distribution Area of the Datacenter where racks and cabinets are located and where the horizontal cablings of the Horizontal Distribution Area are terminated at patch panels.

The Direct Attach Cables are most commonly used in the EDA or Equipment Distribution Area of the Datacenter where racks and cabinets are located and where the horizontal cablings of the Horizontal Distribution Area are terminated at patch panels. They are mainly used for interconnections between servers and switches, storages and switches and two switches.

However today, with the present fast pace life, the Internet is becoming more popular day by day. This means that Datacenters have to find a way to fulfill the customer’s demands for high bandwidth and stability. For this reason they started deploying Active Optical Cables instead of Direct Attach Cables.

Figure 3:
BO253503KXM- BlueOptics© Active Optical Breakout Cable (AOC), 40GBASE-SR4 to 4x10GBASE-SR, QSFP to 4xSFP+, 850nm, Multi-mode, up to 100 Meter Reach

Active Optical Cables (figure 3) use the same technology of accepting the electrical signals. However, with the help of their components, they are able to convert these electrical signals into optical light and transfer it down the optical cable. With this solution they improve speed and data transmission performance, without sacrificing the reliability and the compatibility with the standard electrical ports of the networking devices.

The market for Active Optical Cables continues to grow with each year mainly because of their broad options for application:

  • - InfiniBand QDR, DDR and SDR interconnects. This solution provides very high throughput and very low latency connections
  • - Data aggregation and Backplane applications
  • - 40 GB Ethernet and 10 GB Ethernet Interconnects
  • - Interconnectivity between hubs, switches, routers and servers

Active Optical Cables eliminate the need for an external optical transceiver because the transceiver is fitted on the cable itself. These cables offer a couple of key advantages when compared to Direct Attach Copper Cables:

  • - They offer greater bandwidth, up to 40 GB/s and 100 GB/s with QSFP+
  • - They offer resistance to electromagnetic interference because they are not able to conduct electric current. The electromagnetic interference can eventually cause service degradation and even a complete system failure
  • - They are a lot lighter than the Direct Attach Copper cables, due to their material, making them easy to manage, install and replace.

Even though Active Optical Cables are more expensive to manufacture and purchase than Direct Attach Cables, from day to day their deployment is rising because they guarantee a high bandwidth, stable network connection.