High speed data transmission is the prerequisite for enterprise network deployment. For big data centers, 40G is still the mainstream. For 40G network, 40 gbps transceiver and 40gb ethernet cable are important components, and they can be classified according to transmission distance. For long transmission distance, there are 40G LR4 QSFP+ transceiver and singlemode fiber cable; for short transmission distance, there are 40G SR4 QSFP+ transmission and multimode fiber cable. In addition, for 40G short link, there is QSFP+ DAC cable. Two types of QSFP+ DAC cables are available on the market: 56G QSFP+ DAC vs. 40G QSFP+ DAC, what’s the difference between them? This article will make a comparison.

56G QSFP+ DAC Vs. 40G QSFP+ DAC: Same construction

We know that DAC cable is a kind of high speed passive copper cable with one connector on each end. The connectors are not real optical transceiver modules but in the form of optical transceiver module. DAC twinax cable Therefore, QSFP+ DAC consists of two QSFP+ transceiver style connectors and one twinax copper cable. With the same construction, the operation of 56G QSFP+ DAC and 40G QSFP+ DAC in 40G network deployment is the same, too. Just plug the connector into 40G QSFP+ port on the switch on both sides, and then you can get 40G link. Here is a figure of QSFP+ DAC cable for you.


56G QSFP+ DAC Vs. 40G QSFP+ DAC: Different protocols

As qsfp+ passive copper cable, both 56G QSFP+ DAC and 40G QSFP+ DAC are QSFP MSA compliant. But 40G QSFP+ DAC supports 40G InfiniBand 8x DDR, 4x QDR, 10G/40Gigabit Ethernet, Fibre Channel, while 56G QSFP+ DAC supports 40G InfiniBand 4x FDR, 56Gigabit Ethernet, Fibre Channel. What’s the different between InfiniBand DDR, QDR and FDR? InfiniBand (abbreviated IB) is a computer-networking communications standard used in high-performance computing that features very high throughput and very low latency. It is used for data interconnect both among and within computers. InfiniBand is also used as either a direct or switched interconnect between servers and storage systems, as well as an interconnect between storage systems. And the following figure shows InfiniBand specification. We know that QSFP+ DAC cable uses four channels for data transmission. And for 40G QSFP+ DAC, it supports 40G InfiniBand 8x DDR, 4x QDR, so each channel can achieve 10G data rate; for 56G QSFP+ DAC, it supports 40G InfiniBand 4x FDR, so the maximum data rate of each channel is 14G.

InfiniBand Specification


Characterized by low Insertion loss and power consumption, qsfp+ passive copper cable is a cost-effective option for 40G data transmission over short distance. As for 56G QSFP+ DAC vs. 40G QSFP+ DAC, the only different is that the former can operate high bandwidth than the latter one. Therefore, if your network needs 40G data transmission, then 40G QSFP+ DAC cable; if you need more than 40G bandwidth, then choose 56G QSFP+ DAC.


Are You Ready For 400G Ethernet?

The rapid development in telecom industry is driving massive demand for higher bandwidth and faster data rate, from 10G to 40G and 100G, will this keep going on? The answer is definitely “Yes”. Some time ago, migration from 10G to 40G or 25G to 100G has been a hot spot among data center managers. While recently, 400G solutions and 400G components are coming. Are you ready for 400G? This article will share some information about 400G Ethernet.

Overview of 400G

In the past couple of years, modules with four 25/28G lanes or wavelengths are the solutions for 100G Ethernet. However, they were expensive at the beginning. Until 2016, the optical components industry has responded to the demands with 100G solutions that already cost less per gigabit than equivalent 10G and 40G solutions, and new developments to further drive down cost and increase bandwidths. The next generation is 400G Ethernet. The IEEE has agreed on PSM4 with four parallel fibers for the 500 meters 400GBASE-DR4 specification that is part of the IEEE802.3bs standard being developed for approval by the end of 2017. The industry is already developing optical components for 400G Ethernet solutions. The following figure shows telecom and datacom adoption timelines.

Telecom and datacom adoption timelines

We can visually see that telecom/enterprise applications first adopted 100G technology in the form of CFP modules. Data centers generally did not adopt 100G interfaces until the technology matured and evolved towards denser, lower power interfaces, particularly in the form of QSFP28 modules. However, as the hyperscale data center market scales to keep pace with machine-to-machine communications needs, data center operators have become the first to demand transmission modules for data rates of 400G and beyond. Therefore, the 400G era is now upon us.

Modules for 400G

We know that the QSFP28 modules for 100G Ethernet and SFP28 modules for 25G Ethernet are now the dominant form factors. Though CFP, CFP2 and CFP4 modules remain important for some applications, they have been eclipsed by QSFP28 modules. To support higher bandwidth, what is the right module for 400G? The first CFP8 modules are already available. QSFP-DD is backward compatible with QSFP, and OSFP may deliver better performance, especially as networks move to 800G interfaces.

CFP8 module: CFP8 module is the newest form factor under development by members of the CFP multisource agreement (MSA). It is approximately the size of CFP2 module. As for bandwidth density, it respectively supports eight times and four times the bandwidth density of CFP and CFP2 module. The interface of CFP8 module has been generally specified to allow for 16 x 25 Gb/s and 8 x 50 Gb/s mode.

100G CFP to 400G CFP8

QSFP-DD module: QSFP-DD refers to Quad Small Form Factor Pluggable Double Density. It uses eight 25G lanes via NRZ modulation or eight 50G lanes via PAM4 modulation, which can support optical link of 200 Gbps or 400 Gbps aggregate. In addition, QSFP-DD module can enable up to 14.4 Tbps aggregate bandwidth in a single switch slot. As it is backwards compatible with QSFP modules, QSFP-DD provides flexibility for end users and system designers.


OSFP module: OSFP (Octal Small Form Factor Pluggable) with eight high speed electrical lanes is able to support 400G (8x50G). It is slightly wider and deeper than the QSFP but it still supports 36 OSFP ports per 1U front panel, enabling 14.4 Tbps per 1U. The OSFP is able to meet the projected thermal requirements for 800 Gbps optics when those systems and optics become available in the future.

OSFP module


Judging from the current trends, 400G will become the mainstream in the near future. But there are still some challenges for it to overcome, such as high capacity density, low power consumption, ever lower cost per bit, and reliable large-scale manufacturing capabilities. You never know what surprise the network will bring to you, let’s wait and see the 400G’s time.

Originally published at: http://www.fiber-optical-networking.com/are-you-ready-for-400g-ethernet.html

How Far Can 25G Ethernet Go?

Seeing from the evolution of data transmission speed and size of data centers, it is not difficult to find that the pressure on the data centers to manage data quality and transmission speed continues to grow, which leads to the need for faster data transmission over the network. Ethernet industry has laid a path to higher networking speeds like 100GbE, and 25G Ethernet has been developed to provide a simpler path to future Ethernet speeds of 50 Gbps, 100 Gbps and beyond. The release of the 25GbE specification provides cost-effective solution for server-to-switch connectivity. However, network will not stop the pace of development. How far can 25G Ethernet go? This article is going to focus on the question.

Overview of 25G Ethernet

25G Ethernet is a standard for Ethernet connectivity in a datacenter environment, developed by IEEE 802.3 task force P802.3by. The IEEE 802.3by standard uses technology defined for 100 Gigabit Ethernet implemented as four 25 Gbps lanes (IEEE 802.3bj). In 2016, 25G Ethernet equipment was available on the market, such as 25G SFP28 transceiver and DAC cable. In addition, 25G Ethernet supports for 100G using QSFP ports that can be converted to 4 lanes of 25 Gbps, like 100G QSFP28 transceiver. Here is a table of 25G Ethernet specification for you.

25G Ethernet specification

Advantages of 25G Ethernet

For 10G ToR to 10G Server connectivity, the simplest cabling solution is to use two 10G SFP+ transceivers and one fiber optic cable. When the network has to be upgraded to 25G Ethernet, the data center manager only needs to replace 10G SFP+ transceivers with 25G SFP28 transceivers. In the same way, we know that in 40G ToR to 10G Server connectivity, one 40G QSFP+ transceiver, four 10G SFP+ transceivers and one MTP to LC breakout cable are utilized. When this network deployment is upgraded to 100G ToR to 25G Server connectivity, the work can be quickly finished by replacing 40G QSFP+ transceiver with 100G QSFP28 transceiver, four 10G SFP+ transceivers with four 25G SFP28 transceivers. It can be easily found that there are some advantages when upgrading from 10G to 25G or 40G to 100G:

  • It can offer both CapEx and OpEx savings through backward compatibility, for investment protection and seamless migrations with consistent rack-design and reuse of the existing cabling infrastructure, avoiding costly and complex changes.
  • The technology utilized in 100G to 25G connectivity is similar to that in 40G to 10G connectivity, but the performance is increased by 2.5 times, thus reducing the power and cost per gigabit significantly.
  • 25G Ethernet provides higher port and system density than a comparable 40G solution.
  • Both power savings and higher density results in lower cooling requirements and operational expenditure for data center operators.

advantages of 25G Ethernet

How Far Can 25G Ethernet Go?

Considering the significant benefits and compelling economics of 25G Ethernet, it is no surprise that the move to 25GbE is accelerating—a recent five-year forecast by industry analysts at the Dell’Oro Group predicts 25G Ethernet will be the dominant Server port speed for new systems by 2018. You can learn about it from the following figure.

forecast for 25G Ethernet

However, never underestimate the need for industry consensus building. At present, 25GbE is mainly used for switch-to-server applications. If it can realize switch-to-switch application, 25G Ethernet may go further.


To be frank, 25G Ethernet indeed gains ground in some aspects compared to 10G and 40G Ethernet. If you plan to deploy 25GbE network, you can visit FS.COM which provides quality 25G SFP28 transceiver and various fiber optic cables.

Originally published at: http://www.fiber-optical-networking.com/how-far-can-25g-ethernet-go.html

How Much Do You Know About 100G DWDM Transceiver?

The pace of the development of network technology has never stopped, from Fast Ethernet to Gigabit Ethernet, 10G Ethernet, 40G Ethernet and 100G Ethernet. To keep up with the pace, many data centers has deployed 100G network. We know that there are many types of 100G transceivers, such as 100G CFP/CFP2/CFP4, CXP and 100G QSFP28. Recently, new 100G DWDM technology has been the choice for 100G network applications over long distance. There are two types of 100G DWDM transceivers—Coherent 100G DWDM transceiver and PAM-4 (Pulse Amplitude Modulation) 100G DWDM transceiver. How much do you know about them? This article is going to give an introduction to 100G DWDM transceiver.

Coherent 100G DWDM Transceiver

Coherent 100G DWDM transceiver refers to coherent CFP transceiver. DWDM CFP transceivers can achieve long-distance data transmission in applications, when previously only SR4/LR4 options were available. It is an important feature enhancement to provide DWDM connectivity in a CFP transceiver for transporting 100G traffic over long distances. What’s more, coherent DWDM transceivers cost less than ER4 and ZR4 CFP transceivers. Now on the market, there are two types: CFP DCO (Digital Coherent Optic) and CFP2 ACO (Analog Coherent Optic).

CFP DCO has a high speed DSP (digital signal processing) chip built in which makes the coherent CFP a real workhorse. The DSP provides the electronic dispersion compensation and this eliminates the need of separate DCMs (dispersion compensation modules) of CFP. As a result, coherent CFP is able to support transmission distance of more than 1000km between sites.

The available CFP2 coherent DWDM transceivers are analog. Judging from the size, CFP2 ACO is half the width of CFP. Apart from this, another difference between CFP2 ACO and CFP is that CFP2 ACO does not has a DSP. In order to take the full advantages of the coherent features, CFP2 ACO requires a separate DSP on the host board. Though the DSP increases the power consumption and cost, it means that there is no need to add DSPs to the board.

PAM-4 100G DWDM Transceiver

PAM-4, adopted by the IEEE, is expected to be the most cost-effective and efficient enabler of 100G and beyond in the data center. PAM-4 makes more efficient use of electronic and optical components by packing two bits for every symbol sent over the fiber. Single-lambda 100G PAM-4 offers the simplest architecture, lowest component count, the most streamlined data path, higher reliability and an easy upgrade path to 400G Ethernet and beyond. And it enables the lowest-cost 100G transceiver. The 100G DWDM transceiver utilizes PAM-4 solution in QSFP28 form factor. For those who want to build an embedded DWDM network, they can use this transceiver directly in the switch. It is a very simple and cost-effective solution, but there is one tradeoff: it needs amplification to get out of the blocks and dispersion compensation to go beyond 5-6km. As a result, a separate DWDM multiplexer with an amplification system and dispersion compensation is required to connect data canters together. In addition, there is one thing to note: before the QSFP28 PAM-4 transceiver is added to an existing DWDM network, the network must prepare right DCM (dispersion compensation module) and amplification system in place.


Utilizing DWDM technology in the transceiver offers a simple and cost-effective solution. For coherent 100G DWDM transceiver, it is suitable for applications which needs longer reach; while for PAM-4 100G DWDM transceiver, it meets the needs of data center operators, such as Microsoft, that intend to turn up 4Tb/s of transmission capacity in a point-to-point fashion between data centers in a 70km metro-distributed network. Which one to choose depends on the specific deployment requirements.

Decoding 25G SFP28 Transceiver

The 25G Ethernet is proposed standard for Ethernet connectivity in a data center environment, developed by IEEE 802.3 task force P802.3by. According to the IEEE standards, 25G Ethernet is now defined for both single-lane and four-lane versions of 25G, such as SFP28 25G transceivers (1×25 Gbps) and QSFP 28 100G transceivers (4×25 Gbps). This article will focus on 25G SFP28 transceiver.

Overview of 25G SFP28 Transceiver

The 25G SFP28 transceiver is a high performance module which supports 25G data rate for data communication applications. It has two types: SFP-25G-SR and SFP-25G-LR. The former one is designed to use a nominal wavelength of 850nm and can operate over OM3 fiber up to 70 meters and OM4 fiber up to 100 meters. It is suitable for short-range data communication and interconnect applications. While the latter one features a highly reliable 1310nm DFB transmitter and PIN photo-detector into duplex LC connector, providing links up to 10 kilometers over single mode fiber. It is designed for long-reach applications. Here is a figure of SFP-25G-SR for you.


Cabling Solutions of 25G SFP28 Transceiver

Generally speaking, 25G SFP28 transceiver is usually used for 25G to 100G connectivity. This part will take 25G SFP28 SR transceiver for example.

Cabling Solution 1. From the figure below we can see that one 100G QSFP28 transceiver can be connected with four 25G SFP28 transceivers via the MTP LC fanout cable. This is the simplest cabling solution for 25G to 100G connectivity.

25G to 100G connectivity with MTP LC fanout cable

Cabling Solution 2. We can deploy the MTP/MPO breakout cassette to accomplish the optical link. As the following figure shows, one end of MTP trunk cable is plugged into the MTP/MPO mm connector interface of 100G QSFP28 transceiver, while the other end is plugged into the MTP port at the rear of the MTP/MPO breakout cassette. Then the LC ports in the front of the MTP cassette and four 25G SFP28 transceivers are connected by four duplex LC patch cables.

25G to 100G connectivity with MTP MPO breakout cassette

Cabling Solution 3. In addition to deploy MTP modular cassette, we can also use fiber enclosure containing MTP fiber adapter panel. In this way, the cabling can be flexible. Since the fiber enclosure can hold up to four MTP fiber adapter panels, the fiber density can be greatly improved. The cabling solution is shown in the following figure. From the left to the right, the 100G QSFP28 transceiver is connected with MPO adaptor on the MTP fiber adapter panel by MTP trunk cable. The MTP fiber adapter panel will be installed in the fiber enclosure. Then another MTP trunk cable connect the MPO adaptor on both MTP adapter panel and at the rear of the MTP cassette. Finally, the whole 25G to 100G connectivity is completed by the connection between duplex LC ports in the front of the MTP cassette and four 25G SFP28 transceivers, using four duplex LC patch cables.

25G to 100G connectivity with MTP MPO breakout cassette and MTP fiber adapter panel

Cabling Solution 4. We can replace the MTP cassette and four duplex LC patch cables with one MTP LC fanout cable. As the following figure shows, the MTP connect interface of the harness cable is plugged into the MPO adaptor on the MTP fiber adapter panel while the other end four duplex LC connector interfaces are plugged into four 25G SFP28 transceivers.

25G to 100G connectivity with MTP fiber adapter panel


By using MTP components, 25G to 100G connectivity can be accomplished with high cost effectiveness. I hope after reading this article, you can have a better understanding of 25G SFP28 transceiver as well as 25G to 100G connectivity.

Know More About 100GBASE-PSM4 QSFP28 Transceiver

There is an interesting phenomenon that multimode fibers are more expensive than single-mode fibers but the transceivers are the reverse. That is because the multimode core diameter is large and easy to align with VCSEL lasers and detectors while the single mode fiber cable is very hard to build and align transceiver components with and requires very expensive alignment equipment. Therefore, multi-mode transceivers are less expensive than single-mode transceivers. Now the 100G Ethernet network has been widely applied in data centers and there are various types of 100G fiber optic transceivers available on the market. Is there a type of 100G single-mode transceiver which can provide a low-cost solution for long-reach data center optical interconnects? The answer is Yes. The 100GBASE-PSM4 (parallel single-mode 4-lane) QSFP28 transceiver can do that.

Overview of 100GBASE-PSM4 QSFP28 Transceiver

The 100GBASE-PSM4 QSFP28 transceiver supports 100G link over eight single-mode fibers (four fibers for transmit and four fibers for receive) with data transmission distance up to 500 meters. It uses four parallel lanes for each signal direction and each lane carries 25G optical signal. In addition, the 100GBASE-PSM4 QSFP28 transceiver is structured with MTP/MPO interface, so it is usually used with single-mode fiber ribbon cable with MTP/MPO connector.

100GBASE-PSM4 QSFP28 transceiver
Working Principle of 100GBASE-PSM4 QSFP28 Transceiver

The figure below shows the working principle of the 100GBASE-PSM4 QSFP28 transceiver. The transmitter side accepts electrical input signals compatible with common mode logic (CML) levels, wile the receiver side converts parallel optical input signals via a photo detector array into parallel electrical output signals. The receiver module outputs electrical signals are also voltage compatible with CML levels. All data signals are differential and support a data rate up to 25Gbps per channel.

working principle of 100GBASE-PSM4 QSFP28 transceiver
Applications of 100GBASE-PSM4 QSFP28 Transceiver

The 100GBASE-PSM4 QSFP28 transceiver can be used for 100G to 100G connection. As the following figure shows, two 100GBASE-PSM4 QSFP28 transceivers are plugged into Host IC, then these two transceivers are connected by MTP/MPO patch cord and MTP/MPO patch panel.

100G to 100G connection with 100GBASE-PSM4 QSFP28 transceiver

From an optical transceiver module structure viewpoint, PSM uses a single uncooled CW laser which splits its output power into four integrated silicon modulators. Therefore, the 100GBASE-PSM4 QSFP28 transceiver can be used for 100G to 4x25G connection. As the following figure shows, the 100GBASE-PSM4 QSFP28 transceiver and four 25G-LR SFP28 transceivers are connected by MTP-LC breakout cable.

100G to 4×25G connection with 100GBASE-PSM4 QSFP28 transceiver

The 100GBASE-PSM4 QSFP28 transceiver meets the requirement for low-cost 100G connections at reaches of 500 meters in applications that fall in between the IEEE multi-wavelength 10 kilometers 100GBASE-LR4 single-mode fiber approach and its multimode-fiber based 100GBASE-SR10 short reach specifications. It can support a link length of 500 meters over single mode fiber cable, which is sufficient for data center interconnect applications.

A Closer Look at 40G QSFP+ SR4 Transceiver

As 40G network has been widely applied in today’s data center cabling system, 40G QSFP+ transceivers gain great popularity among data center managers. And for short data transmission distance, 40G QSFP+ SR4 transceiver is preferred. This article is going to focus on 40G QSFP+ SR4 transceiver and share several cabling solutions for 40G QSFP+ SR4 with you.

Overview of 40G QSFP+ SR4 Transceiver

40G QSFP+ SR4 transceiver is a parallel fiber optic transceiver which means it uses four fibers for transmitting and four fibers for receiving at the same time. Designed with MTP/MPO interface, 40G QSFP+ SR4 transceiver is used together with multimode fiber, such as OM3 and OM4. Working on wavelength of 850 nm, 40G QSFP+ SR4 transceiver can support 40G fiber optic transmission with the link length up to 100 meters over OM3 fiber and 150 meters over OM4 fiber. For application, 40G QSFP+ SR4 transceiver can be used for 10G to 40G and 40G to 40G connections. Here is a figure of 40G QSFP+ SR4 transceiver for you.

40G QSFP+ SR4 transceiver

10G to 40G Connection

Since 40G QSFP+ SR4 transceiver uses four independent full-duplex transmit and receiver channels, the 40G optical signal can be split into four 10G optic signals. Therefore, we can increase the fiber count at the 10G distribution end to realize 10G to 40G connection. As the following figure shows, we can use 12f MPO trunk cable and fiber enclosure. Four 10G SFP+ SR transceivers are inserted into 10G ports on one side, while one 40G QSFP+ SR4 transceiver is inserted into 40G port on the other side. Then the four 10G SFP+ SR transceivers are connected with four duplex LC patch cables which are plugged into LC ports on the front side of MPO fiber cassette inside the fiber enclosure, and the 40G QSFP+ SR4 transceiver is connected with 12f MPO trunk cable which is plugged into MTP/MPO port on the rear of MPO fiber cassette. Finally, the whole optical link is completed.

40G QSFP+ SR4 transceiver for 10G to 40G connectionA

We can also use MPO to LC fanout and MTP fiber patch enclosure which includes MTP fiber adapter panels. This cabling solution is similar to the previous one, but the difference is that the four 10G SFP+ SR transceivers are connected with MPO to LC fanout which is plugged into MTP/MPO port on the MTP fiber patch enclosure. The scenario is shown in the following figure.

40G QSFP+ SR4 transceiver for 10G to 40G connectionB

40G to 40G Connection

The following figure shows the simplest scenario for 40G to 40G connection. Two 40G QSFP+ SR4 transceivers are separately inserted into two 40G switches. Then the two 40G QSFP+ SR4 transceivers are connected by 12f MPO trunk cable.

40G QSFP+ SR4 transceiver for 40G to 40G connectionA

We can also use MTP fiber patch enclosure to achieve better cable management and higher density cabling. The scenario is shown in the following figure. With the use of MTP fiber enclosure, cable management for 40G to 40G connection could be easier. A 48-port 1U rack mount MTP fiber patch enclosure includes up to four 12-port MTP fiber adapter panels with MPO MTP fiber optical adapters on it, here is a figure for you.

40G QSFP+ SR4 transceiver for 40G to 40G connectionB


Designed with parallel transmission mode, 40G QSFP+ SR4 transceiver has a wide range of cabling applications with great flexibility. The cabling solutions mentioned above are just several commonly used ones. As for detailed cabling solutions for 40QSFP+ SR4 transceiver, it is suggested to depend on the practical applications and cabling environments. I hope after reading this article, you can learn more about 40G QSFP+ SR4 transceiver.