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Category: Fiber Optic Transceivers

10G Stacking Over Cat6a or DAC

10G Stacking Over Cat6a or DAC

We have got benefits from the stacking of 10G SFP+ switches for the past decades, and the 10G SFP+ direct attach cable (DAC) makes the stacking low-cost. But when 10GBASE-T becomes a new port choice on 10G switches, stacking on 10G switches has to meet the issue about whether to choose Cat6a or SFP+ DAC. At first people think that Ethernet cable is cheaper and easier to deploy than SFP+ DAC, but later they realized the issue is not only about the cable cost.

  10G stacking-cat6a or DAC

Comparison of Stacking 10G Over Cat6a and SFP+ DAC

Before going on, it should be noted that this discussion is focused on 10G stackable switches that have both 10GBASE-T ports and SFP+ ports (such as Cisco 550X series switches, Dell 8024).

In terms of the cost, one Cat6a cable costs just one third of a 10G SFP+ DAC of the same length. But cable price is not the only factor that contributes to the total budget in building a network. Let’s see some properties of these two technologies.

Power Consumption
SFP+ DAC Cat6a
Power Consumption Per Port 1-1.5 W 4-6 W
Max. Reach 10 m 100 m

Obviously, SFP+ DAC uses much less power than Cat6a cable. It is important to know that for every watt of power consumed, typically two additional watts are needed for cooling. If there is a lot of ports in the stacking, this power consumption will be significant. So when power consumption matters a lot in your stacking, it will be a huge saving to choose SFP+ DAC instead of Cat6a.

10G cable power consumption
More ports mean more power consumption.

Also in a case when low latency is strictly required, like in automated financial trading, it is also better to use SFP+ DAC for 10G stacking. Because for the same links and lengths, Cat6a presents higher latency than SFP+ DAC.

automated financial trading low latency
Automated financial trading requires low latency.

When you have many stacked 10G switches located at different places, i.e. at separate floors or at opposite ends of a hallway, Cat6a can achieve the stacking connection if it is less than 100 m. But typically you’ll be suggested to use fiber link, because the power consumption in long-term could exceed the extra cost for buying 10G fiber optics and cables.

10G stacking distance
The stacking distances affect the cable choice.

As for distances more than 100 m, neither SFP+ DAC nor Cat6a can work. You have to turn to fiber optic patch cable and 10G SFP+ transceiver module.


Considering the total cost and performance of Cat6a and SFP+ DAC for 10G stacking, SFP+ DAC appears to be a better choice in short range. The low power consumption and low latency properties can help accomplish a good stacking, and thus shortening the downtime, improving resiliency, and simplifying administration.

10G SFP+ Copper Transceiver Solution

10G SFP+ Copper Transceiver Solution

It’s said that switch manufacturers are entering into the new fiber transceiver era. Only SFP+ or SFP cages are implemented for future flexibility. And copper ports were only implemented for management purpose so far. However, we cannot deny the fact that there are some applications in the past with 1G where Servers or other components do only have 1G copper ports. So 1G copper SFPs have the right to exist. Now all connections moved from 1G to 10G and the copper ports disappeared so far. But a while ago some vendors started implementing 10G SFP+ copper transceivers to their devices again. One of the main applications in data centers is using SFP+ DAC cables. But the use of RJ-45 cables is often easier than using a copper DAC.

Basic Information on 10G SFP+ Copper Transceiver

The 10G SFP+ copper transceiver is specifically designed for high speed communication links that require 10 gigabit ethernet over Cat 6a/7 cable. This is the first SFP+ transceiver that offers 10Gb/s communication over this type of media. 10G SFP+ copper transceiver uses 10GBASE-T technology, which enables 10 Gigabit Ethernet to operate over balanced twisted-pair copper cable, including Cat6a unshielded and shielded cabling. Compare with 10G optical transmission, 10G SFP+ copper transceiver uses copper cables, which offers great savings and flexibility during network deployment.

Just as all other BASE-T implementations, 10G SFP+ copper transceiver supports lengths up to 100 meters, which gives IT managers a far greater level of flexibility in connecting devices in the data center and accommodating top of rack, middle of row, or end of row network topologies. Moreover, it also gives IT managers the most flexibility in server placement, since it works with existing structured cabling systems.

Reasons to Buy/Advantages of 10G SFP+ Copper Transceiver

With more and more 10GBASE-T network equipment available on the market , data center decision makers will consider to take advantage of the cost savings, convenience, and flexibility provided by deploying 10G technology over balanced twisted-pair copper cabling.

There exist several compelling reasons to buy a 10G SFP+ copper transceiver, both from a network equipment designer and data center manager prospective. And the advantage of 10G copper transceiver can be summarized as follow:

  • Reach: Up to 30m over CAT6a UTP cable, sufficient for all network access use cases
  • Cost: Pay-as-you-grow model that performs for today and scales for tomorrow
  • Reliability: The RJ-45 connector interface is rock solid. No surprises when deployed in your data center.
  • Innovation: Hot–pluggable with a managed soft-start
  • Performance: Full PHY (physical level) presentation, which means nothing is missing
  • Smaller Footprint: Interoperable with any SFP+ cage and connector system
Application Scenarios For 10G SFP+ Copper Transceiver

As it has been mentioned before, 10G SFP+ copper transceiver is based on 10GBASE-T, which has the advantage of being an interoperable, standard-based technology that uses the familiar RJ-45 connector and provides backwards compatibility with legacy networks. Supporting top of rack, middle of row or end of row architectures, 10G SFP+ copper transceiver can extend the life of any switch hardware, without having to change the existing infrastructure. The following pictures present the two application cases for 10G SFP+ copper transceiver.

Case one: Connecting server and/or storage appliances with 10GBASE-T RJ-45 to a SFP+ network switch


Case two: Network upgrade to 10G at edge switches


FS 10G SFP+ Copper Transceiver Solution

FS 10G SFP+ copper transceivers are high performance, cost effective modules supporting a data rate up to 10Gbps with 30 Meter link length over Cat6A /Cat7. It is designed for application where optical connections not possible or direct attached cable (DAC) Connection are too short. Moreover, FS 10G SFP+ copper transceivers are compliant with brands like Cisco and Arista. And every transceiver from FS is individually tested on corresponding equipment such as Cisco, Arista, Juniper, Dell, Brocade and other brands, passed the monitoring of FS intelligent quality control system. For further information on our products, please contact us at

A Glimpse Into the Business of White Box Switches

A Glimpse Into the Business of White Box Switches

White boxes are not something new to us. Since they promise a high level of freedom for networking at a low cost, they have been gaining more and more popularity among customers in recent years. As a piece of hardware, a white box switch can be purchased separately from the software. According to the relevant statistic, this decoupling can save up to 52 percent over the traditional vertically-integrated switch, which often comes at a premium price for the software and fancy logo. When picking up a white box switch, customers can purchase different components from different suppliers. Next, I will show the current situation for the suppliers in the ecological chain of white box switches.

White Box Switches

Current Situation of Suppliers for White Boxes’ Three Major Components
Silicon Suppliers

With little switch silicon suppliers on global market, silicon suppliers that can be selected by white box manufacturers are even lesser because the compatibility must be taken into consideration. Across the world, the main silicon supplier is Broadcom with the newly emerged Cavium being flashed occasionally in the white box market. In China, the largest player in this area is Centec.

Hardware Suppliers

Hardware suppliers are the most important part in the ecological chain of white box switch. They may seem insignificant but the whole cost in this ecological chain hinges entirely on them. Large companies in the Over the Top (OTT) Market may be not interested in software developed by others, so they tend to work on their own software. However, they will never make a hardware by themselves. So, it is impossible for white box manufacturers to cut the price down without the cooperation of hardware suppliers. At present, the main suppliers in this area is Quanta and Accton in Taiwan, China as well as Celestica in Canada. And in China’s mainland, similar enterprises are also on the rise. All these suppliers have their own factories with the ability to manufacture or design the hardware for white box switch. All of them are collectively known as ODMs. Besides, some suppliers may don’t own a factory but they are equipped with strong ability to design the hardware, they can also provide hardware to customers through their cooperated factories.

Software Suppliers

The most exciting changes often fall on the software. There has to be software sitting on the box that makes it possible to program the silicon in the box to do something. That’s the job of the network operating system (NOS). The main commercial software suppliers are mainly distributed at abroad, such as Cumulus, BigSwitch (mainly for SDN), Pica8, Snaproute (with both open-source and commercial version). In China, Centec has its own Centec Network OS (CNOS) as well. In addition to the commercial software, there are also some open source programs on the market such as the OpenSwitch launched by HP, Sonic by Microsoft and OPX by SnapRoute. However, these programs are not mature enough. By comparison, OPX may be a better choice. In China, some large companies have been developing their own white boxes on the basis of OPX.

Way out for Different Suppliers

white box market


With the advantages to take costs and quality in control, these ODMs can make hardware for white boxes in a mass production. Whereas, inadequate capacity for software design and technical support is their disadvantage. Besides, they don’t conduct production unless they get an order, which often leads to a long delivery time. For these hardware OEMs, it is difficult for them to do business with those small-medium sized normal companies. The best way out for them is to make deal with the large OTT enterprises for those customers often come with a large demand and some of them would even pay for part of the deposit in advance. In addition, ODMs are not required to provide software support for those OTT customers. All they need to do is to ensure the quality and control the cost, which can just make up for their limitations and maximize their advantages. Another customer group for ODMs is white box software suppliers. But due to the limited demand and costs, this kind of model has not been developed very well.

Software Suppliers

At present, the most popular software suppliers are Cumulus, Pica8, and SnapRoute. All these companies have their own features and market share. But for most software suppliers, they have been during a hard developing period. The main reason for this is that, for most of the large customers, they tend to have their self-developed operating systems. And as for the small customers, the price advantage for integrating software and hardware is not obvious. So the main customers are mainly distributed at abroad, because their price advantage is more prominent compared with Cisco. The best model for these software players is to focus on other medium or large-scale customers besides those OTT customers. More importantly, they need to persuade hardware ODMs to give them a better price so that they can be combined together to explore the market. For hardware OEMs and software suppliers, cooperation will bring benefits both of them while confrontation can only hurt each other.

Brite-Box Switch Suppliers

Brite-Box switches is another choice for white box switches. They are supported by brand companies like Dell, HP and Juniper. These companies have a strong motivation to gain market share of switches against big brands like Cisco. With their own software and hardware provided by ODMs, they can offer white box switches to customers at a relatively low cost. Although with the advantage of massive channels that allow much more geographic availability and customer care than other white box switch suppliers, these Brite-Box switch suppliers have the embarrassment to compete with their own products line and they can’t meet the requirement of customized service very well.


There exist multiple players in the ecological chain of white box switches, each of them has its own advantages and disadvantages. To find the best way to survive, they have to develop the strong points and avoid the weak points. For example, as it has been mentioned before, hardware ODMs and software suppliers must work and support with each other to cut the cost down, thus creating a broader marker for both of them.

25G SFP28: What Makes It Different?

25G SFP28: What Makes It Different?

Driven by the increasing demand for bandwidth requirement, the 25G Gigabit Ethernet or 25GBASE-T standard has been released in recent years. Then 25G SFP28 assemblies like SFP28 transceiver and SFP28 DAC & AOC, come into being. Though the SFP28 assemblies have been used in a wide variety of high-density and low-power 25 Gigabit Ethernet connectivities, they are still different in optical communications. Why? The following part will uncover it.

Benefits of 25G SFP28 Connections

To meet the growth for bandwidth in data centers, 25G SFP28 brings great benefits for system operators to achieve better network performance.

More Logical Upgrade Paths for Server Connections

Before the 25GBASE-T standard arises, the Ethernet speed upgrade path was clearly defined as 10G – 40G -100G. However, the SFP28 provides a new way for server connections: 10G – 25G- 40G -100G. And since 25G offers a more efficient use of hardware and a more logical upgrade path to 100G, many companies like Cisco, Microsoft and Intel have put it into practice rapidly.


More Cost-Effective Cabling Choices

25G SFP28 takes existing module form factors, such as SFP28 and QSFP28, and allows for a breakout connection that is configurable as either 25G per lane or the full 100G without changing the port on the front of switches. For example, SFP28 twianx cable, also called SFP28 DAC, is a type of 25G SFP28 assembly. It has a similar structure with other DACs like SFP+ DAC or QSFP+ DAC whose connectors are not real optical transceiver. Due to this reason, SFP28 twinax cable is cheaper than SFP28 AOCs and SFP28 optical transceiver, which offers a cost-effective solution for high density, high speed I/O data center applications.

qsfp28 to sfp28 breakout cable

Furthermore, QSFP28 to SFP28 breakout cable provides various cabling choices for switches and servers. In the following figure, there are two different links between the switch and servers: 25G and 50G server links. Both of them use the 100G QSFP28 to SFP28 breakout cables.

Controversial Compatible Problem

SFP28 optics offer various options for data center and high-performance computing networks applications. However, when using them, many users still have questions about their compatibility and would like to compare them with existing optical modules. That’s one reason why it gets so much attention. This part will explain the differences between SFP28 and SFP, SFP28 and QSFP28.

SFP28 Vs. SFP+: Can I Connect SFP28 Ports With SFP+ Ports?

The answer for this question is “yes”. As we all know, SFP+ form factor is defined for 10G speeds. And it was later adopted for 25G but the electrical interface had to be upgraded to handle 25Gbps per lane. The pinouts of SFP28 and SFP+ connectors are mating compatible. Therefore, SFP28 is backwards compatible with SFP+ ports and will work sufficiently. In addition, compared with SFP+, SFP28 has increased bandwidth, superior impedance control and less cross talk in network connections. And SFP28 copper cable has significantly greater bandwidth and lower loss than SFP+ version.

SFP28 Vs. QSFP28: What Are the Differences?

Though there is a number “28” in their names, there are differences between the SFP28 and QSFP28 modules. SFP28 modules support 25Gbps per lane. While QSFP28 supports four independent lanes, and each is 25Gbps. Both of them can be used in 100G networks, but the SFP28 is applied in the form of QSFP28 to SFP28 breakout cables.


As a new-comer, the compatibility and the benefits makes 25G SFP28 different from 10G and 40G in some degree. The advent of 25G changes the connection speed of servers, and the migration path will from 25G to 50G or 100G, which in turn accelerate the development of 25G. 25G SFP28 assemblies, as an important bridge in this progress, are booming now and in the near future.

100G CFP and QSFP28 Modules’ Functional Mode Comparison

100G CFP and QSFP28 Modules’ Functional Mode Comparison

To meet the growing data rates of optical interconnects, 100G optical modules are booming in 2017. And there are many types of 100G optical transceivers in the market such as CFP modules and QSFP28. Those who have experienced in using optical transceivers may know each kind of transceiver has their own functional mode. And knowing this functional mode helps you to choose the suitable 100G optics for your networks.


CFP SR10 is a 100Gbps parallel transceiver for optical communication applications. It supports link lengths of 100 m and 150 m on laser-optimized OM3 and OM4 cable. This transceiver converts the 10-channel 10Gbps electrical input data into 10-channel 850nm optical signals and then coupling them into ribbon fiber array (MPO connector) for 100Gbps optical signal transmission. On the receiver side, the optical signals are converted into electrical data for 10 output channels. Following is the functional diagram.

cfp sr10


CFP LR4 is another member of 100G CFP modules. But its working process is a little different from CFP SR10 module. CFP LR4 uses four channels for transmitting and four channels for receiving. It uses four WDM optical signals and multiplexes them into a single channel for 100G transmission. On the receiver side, it demultiplexes the 100Gbps signals into four WDM optical signals and then converts them into four output channels. Its functional diagram is below.

cfp lr4


QSFP28 SR4 is also a parallel optical transceiver. It offers four channels for transmitting and four channels for receiving, each capable of 25Gb/s operation for an aggregate data rate of 100Gbps on 100 meters of multimode fiber, which is similar to the CFP LR4. However, the QSFP28 SR4 doesn’t multiplex the optical signals into WDM for transmitting. Its functional diagram is shown below.



The functional mode of QSFP28 PSM4 is much similar to that of QSFP28 SR4. It uses four independent transmit and receive channels. Each channel operates at 25Gbps. The difference mainly lies in the fiber they use. QSFP28 PSM4 works on single mode ribbon fiber cable, while QSFP28 SR4 works on multimode ribbon fiber cables.

qsfp8 PSM4


Similar to PSM4, the QSFP28 CWDM4 also uses 4x25Gbps to achieve 100Gbps. But the difference is that the CWDM4 utilizes an optical MUX and DEMUX to reduce the fiber it needs, which is like the CFP LR4. It only needs a duplex single mode fiber cable to connect two 100G CWDM4 optical modules. At present, CWDM4 links are used in both 100G CFP4 or the QSFP28 optical transceivers.



From the comparison above, we can find that there are mainly two differences between of the functional mode of these 100G optical transceivers. One is the transmission channel and another is the cable type. Except for that, wavelengths, connectors, and other factors also can affect the working performance of optical transceiver in optical connections.

Nowadays, as the competition is getting severe, some vendors have cut the price of 100G modules price. FS.COM is a professional optical products supplier. It offers various compatible optical transceiver for different applications at a lower price. For instance, the 100G QSFP28 SR4 price in FS.COM is only $269. Here is part of the price of 100G optical modules. If you have any need, please welcome to visit our website for more information.

Mode Description Price
CFP-100G-SR10 CFP Cisco Compatible 100GBASE-SR10 850nm 150m Transceiver $1500
CFP-100G-LR4 CFP Cisco Compatible 100GBASE-LR4 1310nm 10km Transceiver $1500
QSFP-100G-SR4-S QSFP28 Cisco Compatible 100GBASE-SR4 850nm 100m Transceiver $269
QSFP-100G-PSM4-S QSFP28 Cisco Compatible 100GBASE-PSM4 1310nm 500m Transceiver $750
QSFP-100G-CWDM4-S QSFP28 Cisco Compatible 100GBASE-CWDM4 1310nm 2km Transceiver $1400