What Does 5G Mean for Optical Communication Industry: Opportunities or Challenges?

With the wave of digital transformation, communication technology has become an important driving force for the transformation and upgrading of all walks of life in the national economy. After that 5G is the future of the communication industry. However, what does 5G mean for optical communication industry: opportunities or challenges?

Undoubtedly, 5G surely promotes the development of optical industry. At the process of promotion, what it brings for optical communication industry is not only opportunities but also challenges. On the one hand, for optic fiber, optical module, optical access network, etc, 5G means the opportunity on account that they will benefit from the construction of 5G. While on the other hand, if wanting to achieve real implementation and large-scale application of optical fiber communication in 5G, we still need innovate in the tech and breakthrough in the economical level. Therefore, in some sense, it means the challenge. In the next contents, opportunities and challenges will be respectively introduced in detail.
The Opportunities 5G Brings for Optical Communication
Generally speaking, there exit three beneficiaries with the appearance of 5G in optical interconnection industry.
For one thing, in the optical communication industry, optic fiber is the first beneficiary in the construction of 5G. The frequency band of 5G is high, and the number of base stations possibly 2-3 times that of 4G. According to the requirement of full coverage, it is estimated by Fiber Broadband Association that the amount of optic fiber used in 5G will be 16 times more than 4G. Out of consideration for the coverage density of 4G base stations which is high in China and for the distance between urban areas is only hundreds of meters, it is estimated that the amount of 5G fiber will be 2-3 times that of 4G.
For another thing, The optical module is the second beneficiary. Assuming that the amount of 5G base station is 2-3 times that of 4G, when considering the inhaul/backhaul module, it is expected to bring tens millions of 25/50GHz high-speed module consumption. The flat structure of 5G will bring huge capacity and cost pressure to the system.
Finally, the high-speed optical access network and optical component are the third beneficiary. The 5G architecture allows backhaul/inhaul/fronthaul capacity to expand dozens of times, reaching tens or hundreds of Gbps. It is necessary to introduce CWDM/WDM based on 25G/50G to raise the requirements of cost performance for tunable laser, tunable filter and CWDM/WDM device. Simultaneously, the demands on TWDMPON system, eCPRI system, and ROADM system are possibly increased. 5G's demands for transport network and IP network will be increased. and the demands of flexible routing on OTN/WDM and IP network will also be increased. Besides, some new routing function, such as SR, will be introduced with the trend.
The Challenges 5G Brings for Optical Communication
In the 5G era, the number of base stations will increase greatly. A large number of base stations need fiber optic interconnection, which brings new challenges to optical communication when it brings new opportunities. In the process of 5G development, the optical communication industry faces the challenge in the technology, fronthaul/backhaul capacity, and cost. The existing SAW/BAW/FBAR filters are difficult to be used in high frequency devices. The optical devices are the bottleneck of the fronthaul cost, especially the tunable lasers.
Currently, the peak period of investment on 4G has passed. 5G has become a hot topic and new breakthrough of development in communication industry; meanwhile, 5G is an important national strategy. It is an important factor to stimulate economic investment, leading scientific and technological innovation, realize industrial upgrading, promote economic prosperity. However, the expectations for 5G should be appropriate and timely. The collision of interests between manufacturers and other operators of devices and optical components generates excessive and premature expectations, making little of the inherent logic and the rule of market, technology and economy.


About the 100G Optical Transceiver: Do You Know These Applications?

At present, global telecommunications industry is at the status of steady development, and the broadband users are growing steadily. Along with the increasing demands of global bandwidth and the expansion in the application field of optical communication, the access of fiber bandwidth has become the mainstream of communication mode. Simultaneously, the scale of investment on optical communication devices has also been further expanded. These become the important force to promote the growth of the optical communication industry.
In addition, with the rapid development of the big data market, the constructions of backbone network, access network and data center need to purchase a lot of optical communication products, which brings new market opportunities to the optical module industry. After that, 100G optical transceiver in optical module industry appears and gradually becomes the mainstream trend of market development. In this post, we are going to talk about the various applications of 100G optical transceiver.
100G optical transceiver is an optical module with 100G rate and a form factor such as CFP,CFP2,CFP4, and QSFP28. In 2010 when the first-generation QSFP28 100G optical module emerged in China, Gigalight has began to pay close attention to the development of 100G optical modules, and actively to cater for this trend, as well as to be aimed at modern enterprises and the long distance communication applications in the large-scale data center. Then the following content is about a brief overview for some typical types of 100G optical transceiver.
CFP 100GBASE-LR4 is a CFP single-mode optical module. 100G CFP module supports tunable wavelength on the full C band, 100G Ethernet or OTU-4 signal. At the same time, it also supports 4X25Gbps and 4X28Gbps applications. The each wavelength can be independently tunable, covers all C-bands, and the distance between wavelengths is 50GHz. Different from coherent transmission, the module also uses a unique optical dual binary(ODB)modulation format. In addition, the module also has built-in signal generating function of PRBS to realize link detection, convenient for deployment, power consumption less than 24W.

CFP2 100GBASE-LR4 is a high-speed CFP2 optical module that is used in 100G devices for the connections of data center and metropolitan network. It fully supports IEEE 100GBASE-ER4 and ITU-T G.959.1 OTU4 standard (4L1-9C1F), can achieve stable reception sensitivity in wide dynamic input range based on SOA; it is fully compatible with CFP module, and its power consumption is lower than 9W.

CFP4 100G-LR4 is a high-speed single mode CFP4 optical module. All CFP4 devices are compatible with MSA(Multi-Source Agreement), which means that it supports the same rate as CFP2 and CFP, but the power consumption is low than CFP2 and CFP (the maximum power consumption is only 6W). The size of CFP4 optical module is half of that of the CFP2 module, 1/4 of that of CFP module. After that, it is more attractive in new ultra high bandwidth data center and core router field.
100G QSFP28 LR4 is a high-speed QSFP28 optical module. Its working wavelength is 1310nm; its maximum transmission rate is 103.1Gbps, and the maximum transmission distance is 10km. Moreover, the module integrates 4x25Gbps data channel; the typical power consumption is 3.2W. It supports digital diagnosis function, and the performance of optical eye diagram and electric eye chart is excellent.


The trend in the 100G market is to achieve higher density, lower cost, lower power consumption and less heat dissipation. Gigalighgt is a company dedicated to R&D and design of optical communication products and to providing system solutions. Gigalight optical modules and related optical communication products have strict QC system and quality guarantee. Furthermore, in the design, electronic components are optimized, so that the performance is more stable, power consumption is lower. Above is the shared contents today. More details are at Gigalight.com.


A New Cost-effective Solution for 100G Network:100G CFP4 Optical Transceiver

At the process of gradual network upgrade from 10G-40G-100G, 40G/100G optical components are widely applied in various industries, especially in the optical interconnect industry. In the next few years, 100G products will continue to prevail. At the same time, optical communication module based on standardized dense wavelength division will attractive more and more attention and will be widely accepted by the market. Thereinto, the CFP optical module is the product under the development of 100G technology.

The 100G CFP optical module, also called as the 100G client module, is a module with hot-pluggable form factor. The CFP series optical modules have experienced the development of CFP, CFP2, CFP4 since the CFP was launched. However, it seems that CFP4 optical module is the most cost-effective solution among them, and is widely praised. Then in this post, the introduction to this solution will be made.

A Brief Introduction to 100G CFP4 Optical Transceiver
The 100G CFP4 module is developed based on CFP, CFP4. It has the same rate as that of CFP/CFP2 optical module, but the transmission efficiency has been greatly improved. Besides, the power consumption is reduced, and the cost is also lower than that of CFP2. Therefore, CFP4 optical module has an irreplaceable advantage. Next, the advantages of CFP4 optical module will be involved in.

100G CFP4 SR4

Advantages of CFP4 Optical Transceiver Module
By comparison, CFP4 optical transceiver is with the following outstanding advantages demanded by most of network users:
1. With higher transmission efficiency: the early 100G CFP optical module achieves the 100G transmission rate through 10*10G channels, and the 100G CFP4 optical module now achieves 100G transmission through 4 25G channels, so the transmission efficiency is higher and the stability is stronger.
2. With smaller volume: the volume of the CFP4 optical module is 1/4 of the CFP, which is the smallest optical module in the CFP series light module.
3. With higher integration of modules: the integration of CFP2 is 2 times that of CFP, and the integration of CFP4 is four times that of CFP.
4. With lower power consumption & cost: the transmission efficiency of CFP4 optical module is obviously improved, and the power consumption is decreased and the cost of system is lower than that of CFP2.

These advantages of CFP4 optical modules have attracted wide attention. Simultaneously, due to these merits, CFP4 will be preferred in the fields, such as data centers requiring ultra high bandwidth and core routers.

Currently, the main types of CFP4 series optics include 100GBASE-SR4 CFP4,100GBASE-LR4 CFP4 in the market. It is believed that 100G will become the future network development with the expansion of 100G deployment in the scale. In addition, the costs in the 100G optical transceiver module and entire 100G network deployment will be reduced with the advancement of network tech. Generally speaking, Gigalight considers that 100G CFP4 bring the new solution for 100G Ethernet. To some degree, it will contribute to the development of 100G at faster pace.


Prediction on the Prospect of 100G Optical Transceiver Market

The topics about 100G optical transceivers are involved in the previous articles. If you still know little of it, then the topic about it will be kept on.
In the development process of 100G optical transceiver, the main problems are high cost, high power consumption on the port. In some sense, these problems are impossible to avoid whether it is via 10G*10 multimode fiber for 100G parallel transmission, or via single-mode fiber based on WDM technology for long-distance transmission. However, with the advancements in technology, these problems can be solved. Well, after that, how about the prospect of 100G optical transceivers? This article will make an analysis to it.

The Application Objects of 100G Optics
The transmission rate is different in different application scenarios. To predict the market situation of 100G optical module, it is necessary to know its application objects at first. According to some materials, data centers can be roughly divided into two categories: Internet data center and enterprise data center. From the perspective of the scale and usage of the data centers, the demand for 100G network in Internet data centers (including some operators) is more urgent, which does not mean that enterprise data centers do not need to deploy 100G networks, but the scope is not so wide.

Types& Features of 100G Optical Transceivers
Three main types of 100G optical transceivers will be introduced in the following content, respectively QSFP28 100G SR4, QSFP28 100G PSM4, QSFP28-100G CWDM4(for more types, maybe you can visit gigalight.com )
1.    QSFP28 100G SR4 Optical Transceiver
The wavelength of  QSFP28 SR4 is 850nm, and the interface type is 12-fibers MPO (Intermediate 4-fibers channel is not activated). It is with 4 channels combined with 8-fibers multimode fiber, each channel supporting 25G to achieve 100G rate.
Features: the interface, same as that of QSFP-40G-SR4, can be directly upgraded from 40G  to 100G. The optical module is usually connected with OM3 and OM4 multimode fiber, respectively to support the transmission distance of 70 meters and 100 meters (the recently-published technology is possible to support  transmission distance of 200 meters via OM4 optic fiber).

2.    QSFP28 100G PSM4 Optical Transceiver
QSFP28 PSM4 transmission mode is similar to that of QSFP28 100G SR4. Each channel supports 25G in 4 channels. This optical module uses single-mode optic fiber as the transmission media and the wavelength is 1310nm.


Features: adopting the QSFP28 port, able to reach transmission distance of 500ms via the single mode optic fiber, which makes it have a certain advantage in the market.

3.    QSFP28 100G CWDM4 Optical Transceiver
Features: the coarse wavelength division multiplexing technology based on single-mode fiber has been relatively mature, but QSFP28 CWDM4 has not been formally approved by the IEEE standard group. Currently, the technology standard is unified and promoted by CWDM4 MSA.


The Prospect of 100G Optical Module Market
According to the above overviews of them, the analyses on the prospect of 100G optical transceiver is as follows.
1.    100G SR4 QSFP28 Optical Transceiver
The development prospect of this optical module is pretty good. Although it has some limitations on the transmission distance. But with the upgrade of technology, these issues will be solved. Besides, it is with these advantages :
l  It is accorded to the standardized applications
l  It can directly disintegrate one 100G interface into 4 independent 25G interfaces via adopting  the 1/4 of MPO/MTP to LC  patch cable on the interface of 100G network device. After that, the type of the switch interface can be unified, and the cost can be also reduced.
l  Its overall price is one of the most cost-effective options at present.
l  Its interface is the same as that of  QSFP-40G-SR4, which makes it easy for the upgrade from 40G to 100G.

2.    100G PSM4 QSFP28 Optical Transceiver
The transmission distance of this optical module can reach 500m, which can meet the requirements of most data centers for transmission distance. In addition, it also has some advantages in cost, so that it is competitive in the market. However, its price is less possible to drop, and the post-maintenance cost is high. Generally speaking, it is difficult to become the mainstream.

3.    100G CWDM4 QSFP28 Optical Transceiver
The optical module for long distance transmission is suitable for the application of super large data center backbone, as well as the 100G connections between building backbones in the industrial parks of data center. On account that the application is not approved by the IEEE standard group, there will exist certain limitations. It is available for part of users in large scale Internet data center. Simultaneously, it is predicted that 100G CWDM4 will not become the mainstream of 100G applications in the data center, but a small part of the main application in the large-scale 100G data center market.


It is seen from above analyses, the different interfaces of 100G module have different application emphases, so that their applications and prospects are also different.  Hoping this post will be beneficial to some users to deploy 100G data center.


Do You Know These Tips about CFP?

On account that the size of CFP optical module is too large to meet the high density demand of data center, the CFP-MSA Committee defines two new CFP series optical modules, namely CFP2 optical module and CFP4 optical module. Compared with the existing CFP, CFP2 and CFP4 will be respectively double and quadruple front panel port density, so 100G CFP optical module has three different sizes of form factor. This post will have an introduction to CFP/CFP2/CFP4 optical transceivers.

Introduction to CFP/CFP2/CFP4 Optics
This CFP transceiver is designed after SFP transceiver interface, but it supports much larger internet speed, which is realized by using 10×10Gbit/s in each direction. The C stands for the Latin letter C, meaning the number 100 (centum). Among these three CFP form factors, the size of the CFP optical module is the largest; the CFP2 optical module is 1/2 of the CFP; the CFP4 optical module is 1/4 of the CFP. (The size of the three modules, as shown in the following figure). It is necessarily reminded that CFP/CFP2/CFP4 optical modules can not be replaced for use with each other, but they can be simultaneously used in the same system.


CFP optical module supports transmission over a single mode and multimode fiber at various rates, protocols and link lengths, including all Physical Media Dependent (PMD) interfaces in IEEE 802.3ba standard.
The CFP optical module is designed on the basis of a small, pluggable optical module (SFP) interface. It is larger in size and supports 100Gbps data transmission. The CFP optical module can support single 100G signal, OTU4, one or more 40G signals, OTU3 or STM-256/OC-768.
The 100G CFP2 optical module is often used for a interconnect link of 100G Ethernet, and the transmission efficiency is higher than that of the CFP. Simultaneously,  the size is smaller than that of CFP which is suitable for higher density wiring. The 100G CFP4 module has the same rate as that of CFP/CFP2 optical module, but the transmission efficiency has been greatly improved. Besides, the power consumption is reduced, and the cost is also lower than that of CFP2. Therefore, CFP4 optical module has an irreplaceable advantage. Next, the advantages of CFP4 optical module will be involved in.

Advantages of CFP Optical Transceiver Module
1. With higher transmission efficiency: the early 100G CFP optical module achieves the 100G transmission rate through 10*10G channels, and the 100G CFP4 optical module now achieves 100G transmission through 4 25G channels, so the transmission efficiency is higher and the stability is stronger.
2. With smaller volume: the volume of the CFP4 optical module is 1/4 of the CFP, which is the smallest optical module in the CFP series light module.
3. With higher integration of modules: the integration of CFP2 is 2 times that of CFP, and the integration of CFP4 is four times that of CFP.
4. With lower power consumption & cost: the transmission efficiency of CFP4 optical module is obviously improved, and the power consumption is decreased and the cost of system is lower than that of CFP2.

Above all is about the tips of CFP optics that you should know, hoping it will be beneficial to you in the latter applications. In addition, for above mentioned  CFP series optical transceivers, Gigalight can offer them for you. Of course, you can also custom them from Gigalight.


Can QSFP+ Optics Be Plugged on the Port of QSFP28?

100G Ethernet is developed at the fast pace. With the prevalence of 100G network, various issues happen in the process of network establishment. For example, 100G QSFP28 optics commonly used in daily life can be available for 10kms transmission distance in 100G applications via WDM tech. However, there is an non-negligible fact that the price of WDM device is high and the utilization of QSFP28 optical transceiver can not still satisfy the needs when the transmission distance is above 10kms. Therefore, QSFP+ optics are needed on the 100G switcher. Well, at this time, the question is whether QSFP+ optical module transceiver can be plugged on the QSFP28 port of the 100G switcher or whether QSFP28 optical module can be utilized on the QSFP+ port. In this article, the answer will be revealed for you.

An Overview of QSFP28 Optical Transceiver
100G QSFP28 optic fiber module is a hot-pluggable transceiver module designed for 100G data rate. “28” means each lane carries up to 28G data rate. The QSFP28 has 4 electrical lanes that can be used as a 4x10GbE, 4x25GbE, depending on what types of transceivers are used(the main types of QSFP28 optics consist of 100G QSFP28 SR4, 100G QSFP28 LR4, QSFP28 CWDM4 and QSFP28 PSM4, shown as the pic ).

Main Types of QSFP28 Optics

A Brief Introduction to QSFP+ Optical Transceiver

QSFP+(Quad Small Form-factor Pluggable Plus) is the most common 40GbE interface type, and also as a high-density 10GbE interface via QSFP+ breakout cables. It connects a network device (switch, router, media converter or similar device) to a fiber optic or copper cable, supporting data rates of 4×10Gbps and supporting Ethernet, Optic Fibre Channel, Infiniband and SONET/SDH standards with different data rate options. Compared with CFP (C form-factor pluggable) transceiver modules, QSFP+ transceiver modules are more compact and more suitable for port-density application. QSFP+ supports the data rate of 40G, 4 channels for transmitting and 4 channels for receiving, each lane carrying 10G. QSFP+ can break out into 4x10G or 1x40G connection.


Can QSFP+ Optics Be Plugged on the Port of QSFP28?
QSFP28 optical transceiver is similar to QSFP+ in the form factor and size, and 25Gb/s is available in per channel of QSFP28 optics. While 10Gb/s is available in the per channel of QSFP+ optics. Therefore, the port of QSFP28 can be backward compatible with QSFP+ optical transceiver.
A 100G QSFP28 port can generally take either a QSFP+ or QSFP28 optics. If the QSFP28 optics support 25G lanes, then it can operate 4x25G breakout, 2x50G breakout or 1x100G (no breakout). The QSFP+ optic supports 10G lanes, so it can run 4x10GE or 1x40GE. If one uses the QSFP+ transceiver on QSFP28 port, one has to keep it in mind that single-mode/multimode (SR/LR) optical transceivers, and  twinax/AOC products are for options.
However, on the contrary, QSFP28 optics cannot be plugged on the QSFP+ port, which is due to that the requirements for the data rate can not be satisfied. There is a rule about mixing optical transceivers with different speed—it also depends on the optics and the ports. Two ports of the optical transceiver module have to match and form factor needs to match as well. Additionally, port speed needs to be equal or greater than the optic used.

 It can be concluded that QSFP+ optical transceiver module can be connected on the QSFP28 ports, but QSFP28 optics cannot transmit 100Gbps on the QSFP+ port. More information about QSFP28 optics and QSFP+ optics are at Gigalight


A Detailed Overview of 100G Optical Transceiver

In past two years, the development of optical industry mainly focuses on the deployment of 100G network, which contributes to the fast development of 100G optical transceivers in data center markets. Currently, the 100G optical module mainly consist of CXP optical module, CFP, CFP2, CFP4 optical module and QSFP28 optical module. Then this post will have a detailed overview of 100G optic fiber modules.

CXP Optical Transceiver
CXP is targeted at the clustering and high-speed computing markets. Therefore,  it is also can be called as high-density CXP. Technically, the CFP will work with multimode fiber for short-reach applications, but it is not actually optimized in size for the multimode fiber market, which is due to that the multimode fiber market requires high panel density to a large extent. The CXP is created to satisfy the high-density requirements of the data center, targeting parallel interconnections for 12x QDR InfiniBand (120Gbps), 100GbE, and links between systems collocated in the same facility. CXP is currently standardized by the InfiniBand Trade Association.
Moreover, in structure, the CXP is 45mm in length and 27mm in width, slightly larger than that of an XFP. It includes 12 transmitting/receiving channels in its compact form factor, which can be realized via a connector configuration similar to that of the CFP. In some sense, the CXP enables a front panel density higher than that of an SFP+ to run at 10Gbps. In applications, typical applications of CXP in the data center include 100GE over Copper (DAC with CXP connectors): 7m (23ft) and 100GE over multimode fiber: CXP for short reach applications (CFP is used for longer reach applications).

CFP Optical Transceiver
CFP, short for C form-factor pluggable, is a multi-source agreement to produce a common form-factor for the transmission of high-speed digital signals. The C stands for the Latin letter C used to express the number 100 (centum), since the standard is primarily developed for 100 Gigabit Ethernet systems. In fact, CFP also supports the 40GbE. When it comes to CFP, it can be defined as multipurpose CFP.
CFP is designed after the Small Form-factor Pluggable transceiver (SFP) interface, but is significantly larger to support 100Gbps. The electrical connection of a CFP uses 10 x 10Gbps lanes in each direction (RX, TX). The optical connection can support both 10 x 10Gbps and 4 x 25Gbps variants. CFP transceivers can support a single 100Gbps signal like 100GE or OTU4 or one or more 40Gbps signals like 40GE, OTU3, or STM-256/OC-768.
Furthermore, CFP form factor, detailedly defined  in the CFP MSA(Multi-Source Agreement), is available for both single-mode and multi-mode fiber and various data rates, protocols, and link lengths, including all the Physical Media-Dependent (PMD) interfaces included in the IEEE 802.3ba standard. For 40GE, its target optical interfaces include the 40GBase-SR4 for 100 meters and the 40GBase-LR4 for 10 kilometers. While with respect to 100GE, there are three PMDs for it: 100GBase-SR10 for 100 m, 100GBase-LR4 for 10 km, and 100GBase-ER4 for 40 km.
Note: about CFP form factors, the CFP-MSA Committee has defined three types as follows:
l  CFP – Currently at standard revision 1.4 and is widely available in the market
l  CFP2 – Currently at draft revision 0.3, half the size of the CFP transceiver; recently available in the market
l  CFP4 – Standard is not yet available, half the size of a CFP2 transceiver, not yet available

QSFP28 transceiver
For QSFP28 optical module, except that it’s a hot-pluggable optical module designed for 100G data rate, it integrates 4 transmitting and 4 receiving channels. And “28” means each lane carries up to 28G data rate. Meanwhile it can do 4x25G/2x50G/1x100G connection.
In addition, the QSFP28 transceiver and interconnect cable are a high-density, high-speed product solution designed for applications in the telecommunications, data center and networking markets. The interconnect offers four channels of high-speed differential signals with data rates ranging from 25Gbps up to potentially 40Gbps, and will meet 100Gbps Ethernet (4x25Gbps) and 100Gbps 4X InfiniBand Enhanced Data Rate (EDR) requirements. QSFP28 is fast becoming the universal data center form factor. QSFP28 transceiver is typically available in two standards—100GBASE-SR4 and 100G QSFP28 LR4. 100G QSFP28 SR4 operates at multimode fiber for a distance of 100m. 100GBASE-LR4 QSFP28 can support a much longer distance of 10 km.


Above all is about the introductions to 100G optical transceiver. Except for above three types, there is another 100G optical transceiver called CPAK in the market. The CPAK optical transceiver is the new module type popular this year. The appearance is similar to the Cisco optical transceiver, but the interface uses the IEEE standard and supports compatibility with other interfaces. More details are at Gigalight


100G QSFP28 CWDM4 vs. 100G CLR4 Optical Transceiver

For the 100G Ethernet, although there are CFP, CFP2, CFP4 and QSFP28 optical modules for options, and QSFP28 transceivers undoubtedly are preferred due to its small form factor, higher transmission rate, longer transmission distance, etc. QSFP28 optics consist of QSFP28 100GBASE-CWDM4, QSFP28 100GBASE-PSM4, QSFP28 100GBASE-SR4, QSFP28 100GBASE-LR4, QSFP28 CLR4 and so on, among of which QSFP28 CWDM4 and QSFP28 CLR4 are the most suitable solutions for one who demands long distance, high transmission rate and low cost. However, what are differences between QSFP28 CWDM4 and QSFP28 CLR4? In this post, the answer will be gotten.
What Is CWDM4 Optical Transceiver?
The 100G QSFP28 CWDM4 optical transceiver is a full duplex, photonic-integrated optical transceiver module that provides a high-speed link with a maximum transmission distance of 2km for 100G Ethernet. CWDM4 interfaces with LC duplex connectors. It uses 4×25Gbps to achieve 100Gbps. Specifically speaking, four lanes with center wavelengths of 1270nm, 1290nm, 1310nm and 1330nm are controlled on the transmit side. On the receiving side, four lanes of optical data streams are optically de-multiplexed by an integrated optical demultiplexer. With an optical multiplexer and de-multiplexer, one just uses a duplex single-mode fiber to connect two 100G CWDM4 optical transceivers.

Why to Choose CWDM4?
CWDM is defined by CWDM4 MSA(Multi-Source Agreement), who targets a common specification for low-cost 100G optical interfaces that run up to 2km in data center applications. It’s with low power consumption, high compatibility, Digital Diagnostic Monitoring (DDM) support, high transmission rate, long transmission distance. In addition to these advantages, its most attractive benefits are with 2km long transmission distance and cost-saving in fibers. It’s exactly what ones want who are troubled by these two issues.

What Is CLR4 Optical Module?
100G QSFP28 CLR4 is an optical module standard defined by 100G LR4 Alliance,  similar to 100G CWDM4 QSFP28 optical module to large degree. It also utilizes single-mode CWDM Coarse Wavelength Division Multiplexingtechnology, and adopts duplex LC interface. It is with 4 channels, each running at 25Gbps to aggregate 100Gbps, and is with 20nm CWDM wavelength spacing between channels (same as 40G LR4). The transmission distance is 2km used with single-mode optical fiber. In the meantime, it’s with and without FEC enabled in the switch to support lowlatency applications.
Why  to Choose CLR4
The motivation for the 100G-CLR4 specification is to provide open, multivendor specification for a costeffective, low power, 100Gbps (4x25.78GBd), CWDM optical transceiver with a reach of up to 2km over duplex singlemode fiber and duplex LC optical connectors. On account of  its various benefits, it satisfies the demands on data rate, transmission distance, connectors, power consumption, etc. Then the advantages of CLR4 are as below:
l  Low power-consumption.
l  Compact transceiver form factor: The 100G-CLR4 Specification is transceiver form-factor agnostic, with QSFP28 as the initial form factor.
l  Compatibility with SMF connectors and cable infrastructure for present and future datacenters,
l  as well as telecom client-side interfaces.
l  Application supports operation with and without Forward-Error-Correction (FEC):
l  Enables use with FEC for increased link margin or operation without FEC for lower
l  power consumption and lower latency.
l  A variety of opto-electronic implementation approaches and technologies.
l  Reach up to 2 km based on practical cabling design such as structured cabling or point to-point cabling.

100G CWDM4 vs. 100G CLR4 Optical Module: What Are Differences?
According to the above introductions to them, the differences between QSFP28 CWDM4 and QSFP28 CLR4 can be concluded(by comparison in the form of table shown as below). Generally speaking, their main difference is that the 100G CLR4 optical module can be used for both fiber links with forward error correction (FEC) functions and fiber links that do not have forward error correction (FEC) functionality. For the fiber link that have forward error correction (FEC) functions, 100G CWDM4 QSFP28 and 100G CLR4 QSFP28 optical module can be used together; while in the fiber links without forward error correction (FEC) functions, 100G CLR4 optical module can also maintain performance of low latency and low power, which makes it more popular in high-performance computing, high-frequency transactions and other areas. 


It seems that the similarities are more than differences between 100G QSFP28 CWDM4 and 100G CLR4. But anyway, both of them are the most cost-effective solution for 2km transmission application in data center.