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Things Should Be Considered When Buying Direct Attach Copper Cables

Things Should Be Considered When Buying Direct Attach Copper Cables

SFP+ DACDirect attach copper cables, namely DAC cables, are a form of optical transceiver assemblies used to connect switches to routers and/or servers. They are becoming increasingly popular in the network industry, mainly because the price difference is so large when compared with regular optics. There are various versions of DACs with different specifications on the market today which make us in difficult choices. So, what should be considered when we buy DAC cables? Just keep reading, you may find the answer in this post.

Choose Passive or Active?

A passive DAC cable, such as the 10GbE SFP+ DAC, is effectively viewed as a transparent cable to the switch and requires little to no direct power to operate. A passive cable therefore passes the signal through it without any modification or processing such as amplification or equalization. Whereas active DAC cable contains electrical components in the connectors that boost signal levels that make data available to transmit for longer distance. In general, active DAC cables are slightly more expensive than passive DAC cables. How to determine which type should be used? In addition to the consideration of cost and transmission distance, the most reliable method is to check the compatible matrix of your switch. Because some of the switch may not support the passive version, like Brocade VDX.

Choose the Right Connector

DAC cable terminated with SFP+ connectors is commonly used in 10GbE networks. However, there are many other connector options for DAC cables which meet the interconnection demands of higher speed networks. Thus, choosing the right connector according to your network requirement is very important. In general, you could choose the SFP+ for 10GbE, QSFP+ for 40GbE, SFP28 for 25GbE and QSFP28 for 100GbE. In addition, breakout DACs like QSFP+ to 4x SFP+ DAC is an ideal choice for 10G to 40G migration.

AWG Is Also an Important Factor

AWG is another important factor of DAC cables. General specifications like 24AWG, 28AWG and 30AWG are available in the market. Always remember a rule when choosing the AWG—the longer the distance, the higher the AWG rating should be.

Choose the Enough Length

The maximum cable length differs from passive and active DAC cables. Generally, passive cable supports 5 meters or shorter lengths. Whereas active cable can support more than 5 meters (up to 15 meters). Thus, when the distance between connection points is less than 5 meters, passive DAC cable is recommended to use but ensure that your switch can support the passive cable (refer to the first guide). When the distance exceeds 5 meters, it is highly recommended to use active DAC cables to ensure the signal is transferred all the way through. The cost may be a bit higher, but the signal is improved and gives peace of mind by creating a trustworthy connection.

DAC cables are a low-cost alternative to traditional fiber and twisted-pair copper cabling in top-of-rack and middle-of-row. When buying a DACs, parameters such as passive or active, cable connector, AWG, length and so on should be properly selected. This post is a simple buying guide for reference. If you want to purchase high-quality and cost-effective DAC cables, it is highly recommended to visit FS.COM or contact for more details.

Optics & Cable Options for Modern Data Center Interconnection

Optics & Cable Options for Modern Data Center Interconnection

With the migration of network architecture in modern data centers, fiber optics is becoming the preferred option for switch interconnect and server I/O, meeting the demands on bandwidth, port density and low-power.

FS.COM puts much emphasis on developing a comprehensive, cost-effective and advanced solution of 10G, 40G, 100G and beyond 100G fiber optics products to help build unprecedented scale, bandwidth, flexibility and efficiency to your modern data center.

The optics and cables are usually used in the equipment distribution area (EDA) of data center, as shown in the below.

data center

Detailed Information

cables & optics

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QSFP+ AOC – A Favored Solution for 40G Network

QSFP+ AOC – A Favored Solution for 40G Network

As the need for increased network bandwidth to meet the global IP traffic demand is growing rapidly, more and more data centers are deploying 40G Ethernet links. And there are various technologies and solutions to be selected for 40G transmission. 40G QSFP+ transceivers, 40G direct attach cables (DACs) and active optical cables (40GbE QSFP+ AOC Cable) are three kinds of fiber optics used to achieve 40G interconnections in data center. Among them, 40G AOCs are very popular and have a broad prospect. In fact, AOCs are widely used in many fields and play an important role in promoting the traditional data center to step into optical interconnection.

What’s AOC?

AOC is a kind of optical transceiver assemblies that is terminated with transceiver-style plugs to be used in the same ports where optical transceivers are used. And 40G AOC is a 4-channel parallel active optical cable, each channel is capable of transmitting data at dates of about 10Gb/s per direction, providing an aggregated rate of about 40Gb/s over multi-mode fiber (MMF) ribbon cables. Unlike DACs, AOCs are active devices, which incorporate active electrical and optical components to boost/receive signal via optical fiber. And they are embodied the latest technology capable of providing the highest data rates.


Why AOC Is Favored in 40G Network?

As an alternative to optical transceivers, 40G AOCs use electrical-to-optical conversion on the cable ends to improve speed and distance performance of the cable without sacrificing compatibility with standard electrical interfaces. Nowadays, active optical cabling is one of the fastest growing technologies in the data center space. QSFP+ AOCs are popular in 40G network for the following reasons.

Less Expensive

Compared with 40G QSFP+ transceivers, 40G AOCs are much more cost-effective solutions for the data center. Firstly, the QSFP+ transceivers terminated to the cable are cheaper than the 40G QSFP+ transceivers for the reason that there are no lasers in the terminated transceivers (the lasers in the transceivers are very expensive). In addition, the AOC eliminates the separable interface between transceiver module and fiber cable. That’s to say, the transceivers are permanently attached to the fiber cables and no patch cables are needed. While the 40G QSFP+ transceivers need to be used together with fiber patch cords which may be expensive (as the following figure shows). Furthermore, since there are no air holes between the transceivers and cables, AOCs can provide protection from environmental pollutants and other user trouble during installation.

QSFP+ AOC link vs 40G transceiver link
Lighter and With Higher Performance

AOCs are originally invented to replace copper technology and to facilitate high-speed data connectivity for storage, networking, and high-performance computing (HPC) applications. It is known to us that DACs are heavy, bulky and require significantly higher power, making it difficult to physically manage the data center. And the nature of electrical signals, electromagnetic interference (EMI) also limits DACs’ performance and reliability. AOCs, however, provide lighter weight, a smaller size, EMI immunity, a lower interconnection loss, and reduced power requirements.

More Customer-Friendly

Consisting of a complete fiber-optic data link (transceivers plus cable) that can be plugged into existing ports, AOCs enable a very rapid introduction of optical connections. AOCs provide customers with access to all the great advantages of fiber (for example, high bandwidth, relatively thin, lightweight cable and so on) in a plug-in format. Furthermore, used in a largely electrical data communications infrastructure, AOCs enable the end users to literally plug into the power and security of a fiber-optics link without any special knowledge of fiber optics.


As people expect more information to be available at their fingertips, our communications systems will need to be quicker—and active optical cable is one of the best solutions to this challenge. Fiberstore provides a wide range of solutions for 40G network, including the above mentioned 40G QSFP+ transceivers, 40G QSFP+ DACs and 40G QSFP+ AOCs. We highly recommend 40G QSFP+ AOCs to be used in data center interconnections. All of our optical assemblies are tested in original-brand switch which ensures the 100% compatibility to your device. For more information or quotation, please contact us via

QSFP+ DACs vs QSFP+ AOCs in 40G Migration

QSFP+ DACs vs QSFP+ AOCs in 40G Migration

It is well known that 1G and 10G data rates are not adequate to meet the future needs of high-bandwidth applications. Thus 40G and 100G Ethernet are the inevitable trends in the future. And as the market for 40G Ethernet will grow faster than 100G Ethernet in the mid-term for practical reasons, products for 40G Ethernet such as 40G QSFP+ transceivers, 40G QSFP+ direct attach copper (DAC) cables and active optical cables (AOCs) are very popular in the market. Although 40G transceivers are usually preferred for the advantage of flexibility, DACs and AOCs are more cost-effective alternative solutions in short reach interconnections. This article will give a detailed introduction to DACs and AOCs and the details on QSFP+ DACs vs AOCs.

What’s QSFP+ DACs and AOCs?

DACs and AOCs are two kinds of optical transceiver assemblies, which are terminated with transceiver-style plugs to be used in the same ports where optical transceivers are used. AOCs are active devices, which incorporate active electrical and optical components to boost/receive signal via optical fiber. DACs can be both passive and active. The passive DACs (often called PCCs) have no active circuitry, which means there is a direct connection between copper cable and QSFP+ transceiver’s printed circuit board (PCB) electrical contacts. While the active DACs (often called ACCs) incorporate active component to boost/receive signal via copper cable. The following figure shows the general internal structure of AOCs and DACs.


As ideal solutions for short-distance interconnection, DACs and AOCs are widely used in data center. The following part will analyze the advantages and disadvantages of DACs and AOCs respectively.


As the development of fiber technology, someone may deem that copper technology is out of fashion. This is not true for DAC cables. In fact, DACs still get their role in the market for the following advantages.

qsfp+ dac

  • Enough data rate for various applications—Today’s DAC cables can support higher data rates than traditional copper interfaces. In fact, DAC cables can offer a highly cost-effective way to establish a 40G link between QSFP+ ports of QSFP+ switches within racks and across adjacent racks.
  • Interchangeability—As the development of copper cable technology, copper DACs are interchangeable and hot swappable with fiber optic modules.
  • Cheap—Since copper cables are much more cheaper than fiber cables, DACs are cost-effective solution over optical transceivers and AOCs for short reach applications.

The defect of DACs is that they are heavy and bulky, making it difficult to be managed. Furthermore, due to the nature of electrical signals, copper DAC is vulnerable to the effects of electromagnetic interference (EMI), such as undesirable responses, degradation, or complete system failure.


Providing less expensive, reliable transport for aggregated data rates up to 40 Gbps, the AOCs offer customers the flexibility of traditional optical modules by interfacing to systems via a standard QSFP MSA connector. AOCs are premium products, offering several benefits over DACs.


  • Greater bandwidth—Needing no equipment upgrades, AOCs have a throughput of up to 40 Gbps with QSFP+ transceivers. AOCs are ideal for the high density signal transmission seen in most data centers and high performance computing applications.
  • Lightweight—Due to the fiber cables, the AOC weighs less than a comparable DAC cable.
  • EMI immunity—Since the optical fiber is a kind of dielectric (not able to conduct electric current), AOCs are immune to electromagnetic energy.

Compared with DAC cables, the drawback of AOCs is that they may be a little expensive for customers.


DACs and AOCs use the same port as an optical transceiver but with significant cost and power savings in short reach applications. This is very important in the 40G migration for the reason that DACs and AOCs can fill the need for short, cost-effective connectivity and provide a power-efficient and cost-effective replacement to 40G optical transceivers. Fiberstore supplies a comprehensive line of high-compatible DACs and AOCs with competitive prices. Each of them is tested in original-brand switch which ensures the 100% compatibility to your device. For more information or quotation, please contact us via

Things You Should Know About Direct Attach Cables

Things You Should Know About Direct Attach Cables

DAC-Direct Attach CableDirect Attach Cable, short for DAC, is a form of high speed cable with “transceivers” on either end. They can be used to connect switches to routers or servers . They are becoming increasingly popular in the network industry and widely applied in storage area network, data center, and high-performance computing connectivity etc. The main reason why DAC is popular in the market is the price difference, compared with the regular optics. Another reason for their increased popularity is that RJ-45 10G is not widely adopted, and most high density 10G switches are delivered with 48x SFP+ ports in 1 Rack Unit. Here are some knowledge you may not know but should know about the DACs.

1. No matter in the related article or in product description of some DACs vendors, there is always a point saying that the active DACs are lighter and thinner than passive DACs. Actually, it is a wrong view of point. If you have an using experience of both active and passive DACs, you may find that there is no difference between them in the weight and appearance.

2. As the first point mentioned, the thickness and weight do not depend on the active or passive function. In fact, they are divided according to their characteristic of AWG (American Wire Gauge). For instance, AWG24 DAC is thicker and heavier than the AWG30. Becuase of the difference of wire diameter, the longer the cable, the more inconvenience AWG24 DAC is, compared with the AWG30. Moreover, there is also limited bend radius. Thus, the longer the distance, the higher the AWG rating should be.

3. When the transmission distance is over 5 metres, active DAC is more suitable than passive DAC. Because it will cause the signal issue when using passive DAC for long-haul transmission.

4. DACs are more cheaper than the regular optics. Because the “transceivers” on both ends of DACs are not real optics. Compared with the regular optics, they are without the real components and just used to transmit the optical signals. And of course, without those expensive optics components, the cost of DACs is much lower. Thus, though using the same port as an optical transceiver, DACs are with significant cost savings and power savings in short reach applications.

5. The main difference between active DAC and passive DAC is that there is a driving chip in the design of active DAC.

active vs passive DACs

6. AOC (Active Optical Cable) is one of the form of DAC which integrates multimode optical fiber, fiber optic transceivers, control chip and modules. With the benefits of AOCs, such as lighter weight, high performance, low power consumption, low interconnection loss, EMI immunity and flexibility etc. AOCs are now considered as the rising star of telecommunications and datacom transceiver markets.


Fiberstore offers a variety of high speed interconnect DAC assemblies including 10G SFP+ Cables, 40G QSFP+ Cables, and 120G CXP Cables to satisfy the demands from 10G to 100G interconnection. All of the Fiberstore’s direct attach cables can meet the ever growing need to cost-effectively deliver more bandwidth, and can be customized to meet different requirements. For more information, please visit or contact over e-mail