Jul 07


Nowadays, the demand for high bandwidth increases and footprints for data center expands dramatically, which makes the migration from 10G to 40G much more necessary than ever before. Under this condition, many enterprises are ongoing or imminent to upgrade their data center network infrastructures. To better cater for our users, two transceivers 40G UNIV and 40G SWDM4 QSFP using SWDM (Short Wavelength Division Multiplexing) technology are compared in the following text, which intends to offer a cost effective transceiver solution for 10G to 40G migration applications. As parallel multimode MPO fiber cabling is much more expensive than Duplex-LC fiber cabling, Duplex-LC fiber patch cords will be used in these two SWDM applications, as a cost saving cabling method.

40G Direct Port-to-Port Connection

QSFP 40G UNIV Transceiver for SWDM Application

QSFP 40G UNIV is a kind of pluggable optical transceiver that fitted with Duplex-LC connector and can work with both single-mode and multimode fiber patch cable, originally released by Arista. Hence, it is also referred to as 40G SMF&MMF transceiver or 40G QSFP universal transceiver. When working with singlemode fiber, the Arista QSFP 40G UNIV can support 40G connection with a reach of 500m; and over OM3/OM4, the transmission distance can be up to 150m. Furthermore, the Arista QSFP 40G UNIV is designed with four 10G channels for transmitting and receiving four individual 10G signals through a single Duplex-LC fiber patch cord, for achieving a total 40G connection, as shown in the following figure.

Arista QSFP 40G UNIV

How does the Arista QSFP 40G UNIV work for 40G connection? The answer is SWDM technology. With the help of SWDM, Arista QSFP 40G UNIV will multiplex four wavelengths 1270nm, 1290nm, 1310nm and 1330nm to transmit four 10G signals over the single Duplex-LC fiber patch cord. And when the aggregate 40G signal passes through the receiver end, it will be demultiplexed into four individual 10G signals again. As a result, an aggregate 40G signal can be transmitted through a single Duplex-LC fiber patch cord. In short, Arista 40G universal transceiver is a very good choice for 40G migration which can work with LC-duplex single-mode or multimode fiber, instead of high-cost parallel multimode MPO fiber cabling.

QSFP 40G SWDM4 Transceiver for SWDM Application

QSFP 40G SWDM4 is an updated optical transceiver that basically works with Duplex-LC fiber patch cord for short 40G fiber link. It has the same working principle that uses SWDM technology as the QSFP 40G UNIV one, but can perform better. How does it do this? Unlike QSFP 40G UNIV working with both single-mode and multimode fiber, the QSFP 40G SWDM4 is designed to work with multimode fiber, which can transmit a multiplexed 40G signal over wide band OM5 at lengths up to 440m. It can also work in multimode fiber OM3 and OM4 with a reach of 240m and 350m, separately. What’s more, the power dissipation of QSFP 40G SWDM4 can be as low as 1.5W* since SWDM technology can match 4x WDM optical architecture with 4x electrical interface.

Similar to the QSFP 40G UNIV transceiver, four different wavelengths, 850nm, 880nm, 910nm and 940nm are used in the QSFP 40G SWDM4 transceiver. To transmit a total 40G signal, these four wavelengths will be multiplexed to carry four individual 10G signals, be transmitted through the Duplex-LC multimode fiber patch cord and finally demultiplexed. To better understand the principle of QSFP 40G SWDM4 transceiver, you can learn the above figure that illustrates how does the QSFP 40G SWDM4 work for a short distance 40G fiber link.

40G SWDM4 Transceivers

QSFP-40G-UNIV vs QSFP-40G-SWDM4, Which One is Better?

After discussion, we can learn that both QSFP 40G UNIV and QSFP 40G SWDM4 transceivers enable network operators to grow the capacity of their networks without laying new fiber cabling. In view of the transmission distance, QSFP 40G SWDM4 transceiver working with OM5 supports a longer 40G fiber link than QSFP 40G UNIV with OM3/OM4, but a shorter 40G fiber link than QSFP 40G UNIV with single mode fiber cable. When taking fiber cabling infrastructure cost into consideration, OM5 cabling costs about 50% more than OM4 and singlemode fiber is also very expensive. Then which one should be selected? Just depending on your network needs, such as the fiber link distance, the budget, etc. To better know the differences between QSFP 40G UNIV and QSFP 40G SWDM4 transceivers, here offers a table that shows their detailed parameters.


May 06

How to Deploy 10G, 40G, 100G in the Same Network

In 2010, 10G SFP+ became the primary equipment interface in data center applications. However, jump to 2017, as demand for greater bandwidth shows no signs of slowing, 40G and 100G transceiver shipments saw a whopping increase. While shipments of 40G and 100G modules are on the rise, the large majority of data center networks don’t undergo a whole replacement of 10G device with 40G or 100G device. Instead, many typically deploy necessary equipment to achieve the coexistence of 10G, 40G, and 100G in the same network. Read this post, and you will get detailed solution.

QSFP+ 40G to 10G

In the following scenario, an upgraded 40G switch is networked to existing 10G servers with a 1×24-fiber to 3×8-fiber MTP conversion cable. At the switch, a cassette combines three 40G ports (QSFP 8-fiber) on the 24-fiber trunk. In the server cabinet, each 40G port is segregated into 10G LC connections to support server connectivity.

QSFP+ 40G to 10G

Note: in this architecture, if you have existing 12-fiber MTP trunks, you can use a cassette with two 12-fiber MTP inputs that breakout into 3×8-fiber MTP strands, instead of deploying a new 24-fiber MTP trunk cable. However, if you have to move to denser and more complicated applications, the 24-fiber MTP solution makes for easier migration.

CFP2 100G Port (10×10)

Like the previous example, the following figure 2 also shows a similar scenario in existing 10G servers, but it uses 100Gbase-SR10 ports on the switch, which requires a 24-fiber connector to drive the 10×10 transceiver port. Instead of breaking into 8-fiber connections, it uses 24-fiber MTP patch cord from the switch to the patch panel in the top of the rack. A 24-fiber MTP trunk connects the switch and server cabinet. The MTP cassette at the top of the server cabinet converts the 100G port into ten individual 10G port with LC connectors.

CFP2 100G port (10x10)

Note: As in the figure 1, in this scenario, if you already have two 12-fiber MTP trunks, you can use 12-fiber MTP adapter panel, then a 2×12-fiber to 1×24-fiber MTP harness cable could be used at the switch to build the same channel.

New Installation for 40G/100G Deployment

Figure 3 shows an example of a completely new installation, using 40G/100G right out of the box without any 10G switches in the channel. This method has 40G or 100G port on the core switches, and 40G uplinks at the ToR switches. The patch panels at the top of each rack use MTP bulkhead, with all 8-fiber cords from one QSFP port to the next.

40G100G Deployment - New Installation

In this architecture, we can either use 24-fiber trunks that break into 40G ports, or create trunks with 8-fiber strands on every leg, with 8 fibers per 40G or 100G port, as shown in the diagram above. However, we have to pay attention that with 8-fiber legs, the density will become a challenge. In addition, 12-fiber MTP trunks are avoided in this scenario, since integrating existing 12-fiber trunks with 8-fiber connectivity on the patch cord creates fibers unused.

Deploying 10G, 40G, 100G in the same network can effectively avoid costly upgrades that require ripping out cabling and starting over with a new network architecture. This post have provided three solutions. All the devices in these three scenarios can be purchased in FS.COM. If you are interested, kindly visit FS.COM.

Apr 21

100G QSFP28 and CFP Transceiver Cabling Solutions

By the end of 2016, 100G Ethernet has been widely deployed and becomes a significant portion in data center. Many network-equipment developers are motivated to introduce 100G devices like CFP and QSFP28 modules that consumes as little real estate and power as possible, while achieving necessary price points and delivering superior performance. This post is heading to talk about these two 100G modules and their cabling solutions.

CFP: Out With the Old

Specified by MSA among competing manufacturers, CFP is the first generation 100G transceiver which is designed after the SFP interface, but is significantly larger to support 100Gbps. As we all know, the original CFP has very large size, and in order to meet the need for higher performance and higher density in data center, there is the development of CFP2 and CFP4 specification, which specify a form-factor of 1/2 and 1/4 respectively in size of the original specification. Commonly used CFP/CFP2/CFP4 transceivers are available in 100GBase-SR10 and 100GBase-LR4.

100GBase-SR10 and 100GBase-LR4 CFP

QSFP28: In With the New

QSFP28 is the latest 100G form factor, which is a high-density, high-speed product solution designed for applications in the telecommunications, data center and networking markets. It utilizes four channels of respective signals with data rates up to 25Gbps to meet 100Gbps Ethernet requirement. 100GBase-SR4 and 100GBase-LR4 are two main types of QSFP28 module. The detailed specifications of these two QSFP28s are shown in the following table.

100GBase-SR4 and 100GBase-LR4 QSFP28

100GBase-SR10 Cabling Solution

100GBase-SR10 CFP uses a 24 strand MPO cable for connectivity (10 Tx and 10 Rx with each lane providing 10Gbps, leaving 4 channels unused). It can support maximum link length up to 100m and 150m respectively on OM3 and OM4 fiber cable. 100GBase-SR10 can also be used in 10×10 Gigabit Ethernet modes along with ribbon to duplex fiber breakout cables for connectivity to ten 10GBase-SR optical interface.

100GBase-SR10 CFP Cabling Solution

100GBase-SR4 Cabling Solution

Like 100GBase-SR10, 100GBase-SR4 QSFP28 also uses laser optimized OM3 and OM4 multimode fiber for indication. But 100GBase-SR4 QSFP28 utilizes 12f MPO trunk cable for connectivity (4 Tx and 4 Rx, leaving the middle four unused), which makes it possible to reuse 40GBase-SR4 fiber assemblies when upgrade from 40G to 100G.

100GBase-SR4 QSFP28 Cabling Solution

100GBase-LR4 Cabling Solution

Both 100GBase-LR4 CFP and QSFP28 are both interfaced with LC connector. They uses WDM technologies to achieve 100G transmission over single-mode duplex LC fiber patch cable supporting the link length up to 10km.

100GBase-LR4 Cabling Solution


As the need for high bandwidth is increasing, 100G Ethernet will widespread in data center quickly. Equipped with this basic information about 100G modules and their cabling solutions, we will have little worry upgrading to 100G Ethernet.

Apr 06

100% Fiber Utilization with 2×3 MTP Conversion Cable

When faced with eight-fiber parallel applications, such as 40GBase-SR4 40 Gigabit Ethernet and 100GBase-SR4 100 Gigabit Ethernet, technicians who use conventional 12-fiber MTP cable will waste a third of the fibers in the cable plant (four fibers for transmitting and four fibers for receiving, leaving the middle four unused). To overcome this inefficiency, new 2×3 MTP conversion harness is introduced. 2×3 MTP conversion cable terminated with three 8-fiber MTP connectors on one end and two 12-fiber MTP connectors on the other end can convert the signal from three four-channel transceivers to two 12-fiber trunks, which means 100% utilization of a 12-fiber network. The following text will mainly talk about how 2×3 MTP conversion cable uses all the fibers in 10G to 40G and 40G to 40G connection.

2x3 MTP conversion cable

10G to 40G Connection With 2×3 MTP Conversion Cable

Although upgrading from 10G to 40G Ethernet becomes common in most data centers, it is still impossible to replace all the 10G devices with 40G devices for more cost consumption. There are many solutions that we have introduced in the previous articles used to connect 10G to 40G equipment. 2×3 MTP conversion cable is a cost-effective one. The scenario can be clearly see from the following image. The three 8-fiber MTP connectors terminated at the 2×3 MTP conversion cable are directly plugged into the three 40GBase-SR4 modules(100% fiber utilization), then all cable assemblies will be plugged into the QSFP+ interfaced switch. The conversion from 40G to 10G is the most important step in this connectivity. Here we may use MTP or MPO LC cassette (2x12MTP-12xLC cassette) to connect two 12-fiber MTP connectors at the other end of the conversion cable to twelve duplex LC patch cables. Then all the LC cable assemblies with 10GBase-SR modules will be directly plugged into the SFP+ port switch. The whole connection do not waste any fiber.

10G to 40G connection with 2x3 MTP conversion cable

Identifier FS.COM Products Description
A S5850-48S6Q 48x 10GbE SFP+ with 6x 40GbE QSFP+ Switch
B QSFP-SR4-40G  QSFP+ SR4 optics; 150m @ OM4 MMF, 100m@ OM3 MMF
C 2×3 MTP Conversion Cable 2xMTP to 3xMTP; 50/125μm MM (OM3)
D 2x12MTP-12xLC cassette MTP-12 to LC UPC Duplex 24 Fibers MPO/MTP Cassette, 10G OM3, Polarity A
E Duplex LC Patch Cable Duplex LC; OM3
F SFP-10G-SR SFP SR optics; 300m over OM3 MMF
G S3800-24F4S 20x 100/1000Base SFP with 4x 1GE Combo and 4x 10GE SFP+ Switch
40G to 40G Connection With 2×3 MTP Conversion Cable

In this scenario, the three 8-fiber MTP connectors at the end of the conversion cable are directly plugged into the 40G module, then into 40G switch. In order to make sure all the fibers can be used in this 40G to 40G connectivity, we may use a adapter panel to connect the two 12-fiber MTP connectors of the conversion cable to the two 12-fiber MTP connectors attached at the end of the other 2×3 MTP conversion cable. Then the three 8-fiber MTP harness end with 40G modules will be plugged into the QSFP+ port switch. If you feel confused with my sentences, more clear description is shown in the image below.

40G to 40G connection with 2x3 MTP conversion cable

Identifier FS.COM Products Description
A S5850-48S6Q 48x 10GbE SFP+ with 6x 40GbE QSFP+ Switch
B QSFP-SR4-40G  QSFP+ SR4 optics; 150m @ OM4 MMF, 100m@ OM3 MMF
C 2×3 MTP Conversion Cable 2xMTP to 3xMTP; 50/125μm MM (OM3)
D MTP Adapter Panel Fiber Adapter Panel with 4 MTP(12/24F) Key-up/Key-down Adapters
E 2×3 MTP Conversion Cable 2xMTP to 3xMTP; 50/125μm MM (OM3)
F QSFP-SR4-40G QSFP+ SR4 optics; 150m @ OM4 MMF, 100m@ OM3 MMF
G S5850-48S6Q 48x 10GbE SFP+ with 6x 40GbE QSFP+ Switch

You can gain great value to deploy 2×3 MTP conversion cable, which does not add any connectivity to the link and it allows 100 percent fiber utilization and constitute the most commonly deployed method. However, you have to notice that the use of the 2×3 MTP conversion cable assembly at the core spine switch is not desirable, because patching across blades and chassis is a common practice.

Mar 31

What Should We Prepare for 40/100G Migration?

As data center of all types continue to grow in terms of traffic and size, 40G and 100G Ethernet technology is no longer a pipe dream—it is well on the way and set to become the new standard for high bandwidth and intelligent architecture. Faced with this upcoming trend in data center, what preparation should we do? Read this post, and you will get some details.

LC or MPO Interfaced 40/100G Modules?

Normally, there are two interfaces that 40/100G transceivers use: LC and MPO. LC interfaced modules will be used over single-mode fiber for long distance data transmission, while MPO interfaced modules are commonly deployed with multimode fiber for short distance. However, there are also some transceivers not following this rule. For example, 40GBase-UNIV uses duplex LC connector, but it only supports 150 meters over OM3 or OM4 fiber, and 500 meters over single-mode fiber as we have mentioned in the previous post. Besides, 100GBase-PSM4 is a single-mode module, but it has MPO interface to achieve data transmission. Choosing LC or MPO interfaced 40/100G transceiver totally relies on the transmission distance that your practical application requires.

Type Fiber and Distance Connector
40GBase-SR4 100m(OM3) 150m(OM4) MPO(male/female)
40GBase-LR4 10km(SMF) Duplex LC
40GBase-UNIV 150m(OM3) 150m(OM4) 500m(SMF) Duplex LC
100GBase-SR4 100m(OM3) 150m(OM4) MPO (male/female)
100GBase-LR4 10km(SMF) Duplex LC
100GBase-PSM4 500m(SMF) MPO (male/female)
Keep Budgets Down with Pre-terminated Cabling System

Cost is always the most important factor that every IT managers and ordinary users will concern. Since the technology for 40G and 100G is not as mature as 10G, devices used in these high-speed networks are more expensive, so we should keep our budget down as possible as we can in every aspect in the process of 40/100G migration. Then pre-terminated cabling system is a good choice.

pre-terminated assemblies for 40/100G

Pre-terminated cabling system contains factory manufactured cables and modular components with connectors already attached. It comes in a number of different forms, from connectorized fan-outs and attached or discreet cassette modules to cable bundles utilizing both fiber and copper with protective pulling grips installed over the connectors at one end. With these pre-terminated cabling, the need for labor to make terminations on site will be mitigated. And fewer labor means more savings on the labor bill. As report indicates, using the pre-terminated approach can achieve a saving of 57 percent.

Punch Down Solution   Pre-terminated Cabling
Material Cost              1X            3.2X
Labor Cost              2X            1X
Total              1X            1.3X
Installation Time              10 Hrs            5 Hrs
Future-Proof Your Network with 24-Fiber Infrastructure

In many 40/100G cases, 12-fiber system is more recommended to use between core switched and the equipment distribution area in the data center, but actually, if you want to future-proof your network, try 24-fiber infrastructure. Why? Let’s have a quick comparison.

For typically 40GbE applications, the 4 right and 4 left fibers of a 12 fiber MPO connector are used for transmit and receive while the inner 4 fibers are left unused. For 24-fiber 40GbE application, all fibers are utilized in the MPO plug. 24 fibers, divided by the 8 fibers per circuit that are required, yields 3 full 40GbE connectors. For 100GbE applications, if we choose 12-fiber MPO connector, we need two connector and two MPO trunk cables, the middle 20 fibers are used for transmit and receive 10Gb/s while the 2 fibers on the right are left unused. However, in this case, we just need one MPO 24 connector and one 24f trunk cable. As data centers continue to be crowded with more cabling, with 24-fiber system, about 1-1/2 times more pathway space could be saved.

24 fiber system for 40/100G


With the rapid increase in bandwidth consumption, the migration from 10GbE to 40/100GbE is inevitable. Proper interfaced transceiver, pre-terminated cabling system and 24-fiber infrastructure are required to build a cost-effective and high density 40/100G data center. If you’re interested in the components that we have mentioned above, kindly visit FS.COM.

Mar 17

Some Thoughts Required Before MTP Cabling

To meet system bandwidth needs and provide higher density cable connectivity, building backbones and data center backbones are migrating to 40G and 100G Ethernet network. Making the migration path smooth has become a hotspot. Network designers are turning to MTP components which can provide cost-effective solutions for cabling systems of data centers. We know that MTP components are designed with complex structures, so before you start your 40G Ethernet network deployment, there are a few aspects of MTP cabling that require some thoughts.


First and foremost is the polarity. With the LC connector typically used for 1G and 10G fiber cables, this isn’t a big deal. You can flip the two fiber strands on the LC connector easily to invert the polarity if needed. However, the MTP connector is fixed, you can’t change the ordering of the strands in the connector. Take 12-fiber MTP trunk cable for example, it is made up of 12x individual strands of fiber and one 12-fiber MTP connector on each end. Typically in 40G Ethernet network deployment, the 12-fiber MTP cable transmits optic signals on first 4x strands, and receives optic signals on the last 4x strands. The 4x “transmit” strands in MTP connector on one end need to end up at the “receive” strands in MTP connector on the other end. In other words, 8 of the 12 fibers are used to provide 40G parallel transmission and the polarity of the cable has to be inverted between the two devices. In addition, there are three polarity methods for MTP cabling. Each of them has different features. It is recommended that a method be selected in advance according to the specific requirements of the cabling situation and maintained consistently throughout an installation.

Gender of MTP Connector

Another issue with MTP components to take into consideration is the gender of the connector going into the adapter matter. There are male connector and female connector. And the former one has pins while the latter one has no pins. One cable going into a MTP adapter needs to have a male connector and the other cable must have a female connector. This is not initially obvious to those who have little knowledge about MTP components. If you only have MTP cables with female connectors, they can be snapped into the adapter just fine, but will not work. The figure below shows the difference between the structure of male and female MTP connector.

male and female MTP connector in MTP cabling

Key Position of MTP Adapter

MTP adapter, or MTP coupler, is simple plastic rectangle that holds two MTP connectors together. The other important factor to note about MTP adapter is that they can be either key-up to key-up, or key-up to key-down, and this corresponds to the key position of MTP connector. When the key sits on top, this is referred to as the key up position. On the contrary, when the key sits on bottom, we call it key down position. On a key-up to key-up adapter, the keys are pointed the same direction on both of the connectors. While on a key-up to key-down adapter, the keys are on opposite sides. This can effect the polarity of the fiber link. To have a better understanding of this, here is a figure for you.

key position of MTP adapter in MTP cabling


Being able to provide an easy migration path for higher data rates that will require parallel optics such as 40/100G Ethernet network, MTP cabling is commonly used by network designers to satisfy the increasing demands for higher transmission speed and cabling density. However, before the installation, three major problems—polarity, gender of MTP connector and key position of MTP adapter have to be solved to ensure the smooth data transmission over the optical links.

Mar 07

Can We Use Base-8 and Base-12 Together?

Although 10 Gigabit Ethernet is still marketing its way into the data centers, the need for faster data transfer rates is relentless, which means the migration to 40 Gigabit Ethernet is becoming inescapably compelling. For 40G Ethernet network, there are mainly two connectivity methods, one is Base-8, and the other is Base-12. Base-12 connectivity has had its place in the data center, while Base-8 is a new connectivity that could gain widespread acceptance in the next few years. With these two methods existing in 40G Ethernet network, there comes problems: Which one is more suitable for 40G network, or can we both use these two methods in 40G network? Read this articles, and you will get the detailed answers.

Base-12 Dominates the Market

Base-2 connectivity is the most commonly used one in the past, but as the data center grew to thousands of fiber ports engaged, stringing two-fiber patch cords across all corners of the data center will result in an unmanageable, and unreliable mess. So Base-12 connectivity is introduced. It is designed to develop a modular, high density, structured cabling system which could be deployed in data centers quickly, while also maximizing port densities within the rack space. In this connectivity method, all the fiber optic cables are based on an increment of 12 fiber, like 12-fiber or 24-fiber MTP trunk cable.

Base-12 system using a 24-fiber trunk cable

Base-8 Shines the Light

Base-12 connectivity is common in data center, but here comes a problem when installed it in a parallel system. For example, if we need to use 40GBase-SR4 optics implemented in a 12-fiber infrastructure, four fibers for transmit, and four fibers for receive, leaving four fibers unused per connection, this will lead to a significant and costly loss in fiber network utilization. But Base-8 can be a more cost-effective option for end-to-end MPO to MPO channels and architectures. With 8-fiber infrastructure, the 40GBase-SR4 module will use all the 8 fibers. Base-8 connectivity makes use of fiber links in increment of 8 versus 12. The 12-fiber trunk cables are replaced with trunk cables in increment of 8: 8-fiber, 16-fiber, or 24-fiber trunk cables, etc.

Base-8 system using a 24-fiber trunk cable

Can We Use Base-8 and Base-12 Together?

Although using Base-8 connectivity could decrease fiber consuming in supporting 40G data rates, in fact, in many cases, Base-8 connectivity isn’t a universal solution, and Base-12 may still be more cost-effective. So is it possible to have both Base-8 and Base-12 connectivity in the same data center? The answer could be “Yes” or “No”.

Base-8 and Base-12 Fiber Links Cannot Be Mixed and Matched

It is never possible to directly mix the components of Base-8 and Base-12 connectivity, or plug a Base-8 trunk into a 12-fiber module. Because a Base-12 trunk cable normally has unpinned MTP connector on both ends, and requires the use of pinned 12-fiber breakout modules, while a Base-8 trunk cable is manufactured with pinned MTP connectors at both ends (pinned and unpinned MTP connectors are shown below). So if we plug a Base-8 trunk into a 12-fiber breakout module, just like trying to mate two pinned connectors together, this connection will definitely not work, and vice verse.

pinned and unpinned MTP connector

Base-8 and Base-12 Can be Maintained in the Same Data Center Separately

It is possible to deploy both Base-8 and Base-12 connectivity within the same data center, just as long as the links are separate. Since Base-8 and Base-12 components are not interchangeable, during managing the data center physical layer infrastructure, we should do careful management and labeling practice to ensure we will not mix or mismatch them.


Base-12 connectivity has dominated the 40G network market for years, while the Base-8 connectivity is an additional option in the network designer’s tool kit to ensure that data centers have the most cost-effective, future-proof network available. When using Base-8 and Base-12 in network, make sure that you need to carefully manage and label them, and that the components in Base-8 and Base-12 won’t be mixed.

Jul 20

Optical Transport Network (OTN) for High Speed Service

Nowadays, the SONET/SDH network is an universal network that combines with WDM (wavelength division multiplexing) technique to transmit multiple optical signals over a single fiber. In future networking, high speed transmission is no doubt the migration trend. Inspired by the SONET/SDH network, ITU-T (ITU Telecommunication Standardization Sector) has defined the optical transport network (OTN) to achieve a more cost-effective high speed network with the help of WDM technology.

Generally speaking, OTN is a network interface protocol put forward in ITU G.709. OTN adds OAM (operations, administration and maintenance) functionality to optical carriers. It allows network operators to converge networks through seamless transport of the numerous types of legacy protocols, while providing the flexibility required to support future client protocols. Unlike the previous SONET/SDH, OTN is a fully transparent network that provides support for optical networking on a WDM basis. Since multiple data frames have been wrapped together into a single entity in OTN, it is also known as the “digital wrapper”.

Working Principle of OTN

You may wonder how OTN works in practice. Actually, its working structure and format very resemble the SONET/SDH network. Six layers are included in the OTN network: OPU (optical payload unit), ODU (optical data unit), OTU (optical transport unit), OCh (optical channel), OMS (optical multiplex section) and OTS (optical transport section).

OPU, ODU and OTU are the three overhead areas of OTN frame. OPU is similar to the “path” layer of SONET/SDH, which provides information on the type of signal mapped into the payload and the mapping structure. ODU resembles the “line overhead” layer of SONET/SDH, which adds the optical path-level monitoring, alarm indication signals, automatic protection switching bytes and embedded data communications channels. OTU is like the “section overhead” in SONET/SDH, and it represents a physical optical port that adds performance monitoring and FEC (forward error correction). OCh is for the conversion of electrical signal to optical signal and modulates the DWDM wavelength carrier. OMS multiplexes several wavelengths in the section between OADMs (optical add drop multiplexer). OTS manages the fixed DWDM wavelengths between each of the in-line optical amplifier units.


Advantages of OTN

There are many advantages of OTN. Firstly, it separates the network against uncertain service by providing transparent native transport of signals encapsulating all client-management information. Secondly, it performs multiplexing for optimum capacity utilization which enhances network efficiency. Thirdly, it improves maintenance capability for signals transmitting through multi-operator networks by providing multi-layer performance monitoring.

Migration to High Speed OTN

With the fast evolution of networking, OTN standard is able to reach a higher speed service. Its multiplexing hierarchy allows any OTN switch and any WDM platform to electronically groom and switch lower-rate services within 10 Gbps, 40 Gbps, or even 100 Gbps wavelengths. This eliminates the need for external wavelength demultiplexing and manual interconnects. OTN network is definitely the best solution for future high speed networking over long distance. The picture below shows the OTN mapping diagram for high speed transmission.



Over the years, OTN has never stopped improving itself. Driven by the needs for high speed transmission, OTN combined with WDM is obviously a better choice in networking. It is a cost-effective way to build an optical transport network accommodating high throughput broadband services. I believe more and more people will employ this standard in their own network in the near future.

Mar 23

Considering Three Aspects Before Migrating to 40G

The dramatic growth of bandwidth requirements in data centers has led to the worldwide use of higher-performance optical products for network scalability, management, flexibility and reliability. Currently, 10GbE (Gigabit Ethernet) can’t meet the increasing needs of high speed transmission well for such applications as Big Data, cloud and Internet of Things being introduced in many industries. As such, network migration to 40/100G has already been the industry consensus.

But as the cost for 100G is far beyond what most enterprises can afford and the technology for 100G is still not mature enough, 40G has been a better solution for its lower cost and maturer technologies compared to 100G. Nowadays, some manufacturers are battling for the 40G market, which drives down the 40G deployment price, leading to the even wider deployment of 40G infrastructure. When migrating from 10G to 40G, three aspects should be considered: fiber optic transceiver, transmission media, and pre-terminated MPO assemblies.

Fiber Optic Transceiver

For any telecommunication network, fiber optic interconnection is of great importance. Photoelectric conversion is a necessary part in fiber optic network. The function of fiber optic transceiver is photoelectric conversion, which makes it one of the most commonly used components in the data center.

As for 40G transceivers, two different package forms are available: QSFP+ (Quad Small Form-factor Pluggable Plus) and CFP (C Form-factor Pluggable), with the former more widely-used than the latter. A single 40G fiber optic transceiver may not be expensive. But what a medium-sized data center needs is thousands of optical transceivers, meaning a large sum of money to be spent. In such a case, third party transceivers that are compatible with a variety types of switches come into point. They have the same performances that the original brand transceivers have, but cost less money. When selecting 40G compatible transceivers, cost and quality are very important. Choosing the compatible 40G transceivers from Fiberstore can ensure 100% compatibility and interoperability. The picture below shows the testing of Cisco compatible QSFP-40G-SR4 transceivers on a Cisco switch to ensure its compatibility and interoperability.

QSFP-40G-SR4, under test

Transmission Media

Allowing for several situations that may exist, the IEEE 802.3ba specified the different transmission media for 40G links, including the following listed media:

  • 40GBASE-CR4: 40Gb/s Ethernet over copper cable in short transmission distance.
  • 40GBASE-SR4 (eg. QFX-QSFP-40G-SR4): 40Gb/s Ethernet over four short-range multi-mode fiber (MMF) optic cables.
  • 40GBASE-LR4: 40Gb/s Ethernet over four wavelengths carried by a signal long-distance single-mode fiber (SMF) optic cable.

There also exists hybrid cabling solutions for 40G applications, like QSFP to 4SFP+ breakout cabling assembly. Take QSFP-4SFP10G-CU5M for example, this product listed in Fiberstore is the QSFP+ to 4 10GBASE-CU SFP+ passive direct-attach copper transceiver assembly with 5-meter reach.

QSFP to 4SFP+ breakout cabling assembly, for short reach, 5m

Question occurs: fiber optic cable or copper cable, which should be used in 40G migration? Copper is cheaper. But it can only support 40G transmission limited to several meters. SMF supports the longest 40G transmission distance up to 40 km. As for MMF, OM3 and OM4 are suggested to support short distance transmission. The longest distance that OM3 can support for 40G transmission is 100 m. OM4 can support a longest 40G transmission distance of 150 m. The selection of transmission media should depend on the specific applications.

MPO Assemblies for 40G

The IEEE 802.3ba standard also specifies multi-fiber push-on (MPO) connectors for standard-length MMF connectivity. Most of the 40G multi-mode Ethernet transceivers are based on the MPO technology. It is wise to increase fiber optic density by using MPO technology, but a new problem arises. As the fiber number increased, the cabling and splicing difficulty in data center increased. Unlike traditional two-strand fiber connections, MPO connectors cannot be field terminated easily. Thus, most of the data centers choose the pre-terminated MPO assemblies in 40G deployment, which is more reliable and can save more human labor. Before cabling, determine the cabling lengths and customized pre-terminated MPO assemblies with manufacturers would save a lot of time and money.


Using compatible third party transceivers of high quality for 40G links saves a lot of money. Taking specific applications and characteristics of 40G transmission media into consideration can also help you to save cost. Pre-terminated MPO assemblies are necessary for flexible and manageable cabling in 40G deployment. With these information in mind, cost-effective 40G migration is at the corner.

Mar 16

Overview of 40/100GbE Terminations

Today’s data centers growth is placing increasing demands on the networking infrastructure. For some enterprises, existing 1GbE connections can’t support the growing business requirements well very, not to say 100Mbps connections. In order to accommodate these demands, it’s imperative to upgrade the data center network architecture to 40 or 100 Gigabit Ethernet (GbE) connections. This 40/100GbE network design helps to support not only the current growth, but also the increasing demands in the future.

IEEE 802.3ba 40G and 100G Standard

The Institute of Electrical and Electronics Engineers (IEEE) 802.3 working group is concerned with the maintenance and extension of the Ethernet data communications standard. And 802.3ba is the designation given to the higher speed Ethernet task force to modify the 802.3 standard to support higher speeds than 10Gbit/s, that is 40/100G in 2010. This 802.3ba 40/100G standard encompasses a number of different Ethernet physical layer (PHY) specifications which are supported by means of pluggable modules, like Quad Small-Form-Factor Pluggable (QSFP) and C Form-Factor Pluggable (CFP). As for transmission medium, the transport speeds at 40/100Gbit/s use two methods: parallel optics and copper cables, with the fiber optics solutions allowing more flexibility and greater distance reach.

40GbE Terminations

In most cases, 40GbE connections use a QSFP+ transceiver terminated to receive the multi-fiber push-on/multiplex pass-through (MPO/MPT) trunk. That is, the short-range QSFP+ transceivers (eg. QFX-QSFP-40G-SR4) use multi-mode MPO trunks to establish 40G links. During this link establishment, polarity becomes a consideration when implementing 40GbE switch-to-switch interconnects over multi-strand multi-mode fiber (MMF). Method B polarity is recommended for the functional link.

QSFP+ transceivers are also able to run on single-mode fiber (SMF) for long reach. These links are Little Connector (LC) terminated and can run up to 40km, mainly used for 40GbE interbuilding connections. Take QSFP-40G-ER4 for example, this 40GBASE-ER4 transceiver supports link lengths up to 40km over SMF with duplex LC connectors.

The QSFP+ transceiver can also be used for 40GbE to 4x10GbE partitioned applications, that is QSFP+ to 4SFP+ fan-out cabling assemblies. One end of the connection is terminated using a MPO/MPT configuration with four individual pairs terminated with LC connectors at the other end. The image below just shows the QSFP+ to 4SFP+ Active Optic Cable (AOC) assembly.

QSFP+ to 4SFP+ AOC, 40GbE to 4x10GbE partitioned application

100GbE Terminations

100GbE connections use a CFP transceiver. Two CFP options are dominant in the industry: CFP2 and CFP4. The primary differences between the two are physical density and transmit/receive lane configurations. More specifically, CFP2 supports 100GBASE-SR10, 100BASE-LR4, and 100GBASE-ER4 optical interfaces, while CFP4 doubles the port density on the line card and supports 100GBASE-SR4, 100GBASE-LR4, and 100GBASE-ER4 optical interfaces.

CFP options, for 100G transmission

40/100GbE Termination Benefits

The 40/100GbE network infrastructure provides the following benefits:

  • Reduced data center complexity: As virtualization increases, the use of fewer physical servers and switches has been made possible by 40/100GbE network infrastructure.
  • Reduced total cost: Since 40/100GbE network system simplifies the local area network (LAN) and cable infrastructures, the potential cost reduction in virtualization environment is also accessible. Besides, the 40/100GbE network infrastructure requires fewer data center space, power, and cooling resources.
  • Increased Productivity: Faster connections and reduced network latency provide network designers with faster workload completion times and improved productivity.

Upgrading network architecture to support speeds greater than 10GbE, that is 40/100GbE, is essential in optimizing data center infrastructure, giving a hand in moving quickly in respond to business needs. At the same time, the services and value brought by information technology itself can also be enhanced.


The high-performance 40/100GbE network architecture simplifies the cabling infrastructure and reduces per-server total cost of ownership, capable of allowing high speeds at 40/100Gbit/s. Fiberstore offers a large selection of 40/100G optical modules, as well as 40/100G fiber optic-based cables and copper cables. For more information about 40/100GbE solutions, you can visit Fiberstore.