An Overview of CWDM Optics: Definition, Types& Standards, Advantages &Applications

With the continuous development of optical communication industry, CWDM optical module, as a very cost-effective solution for network connection, is widely applied in Gigabit Ethernet and fiber channel applications, etc. However, it seems that there are still people confused about its some knowledge. For example, what is the CWDM optical module? What are the advantages of CWDM optical transceiver? What are the applications of CWDM optical transceiver? Then the answers will be gotten after reading this article.

What Is CWDM Optical Transceiver?
CWDM optical module is a kind of optic fiber transceiver adopting CWDM technology. It can be connected with wavelength division multiplexer. It can multiplex different optical signals with different wavelengths into one signal for transmission over one fiber by utilizing the theory of wavelength division multiplexer. Simultaneously, it can also demultiplex multiplexed signals on the receiving end so that the optic resources can be saved. Therefore, the CWDM optical module is regarded as a low-cost and cost-effective network solution.

Types and Standards of CWDM Optical Transceiver
On the one hand, in terms of standards, CWDM optical transceiver is conformed to these standards:

• Conformed to the RoHS standard
• Conformed to IEEE standard 802.3 (Gigabit Ethernet 802.3z, 802.3ah, FastE 802.3u)
• Accorded with physical interface specification FC-PI-2 of optical fiber channel.
• Compatible with SONET/SDH optical standards
• Conformed to SFP multisource Agreement(MSA)

On the another hand, with respect to types, CWDM optical module accorded with various standards can be divided into CWDM SFF optical module, CWDM SFP optical module, CWDM GBIC optical module, CWDM SFP+ optical module, CWDM XFP optical module, CWDM X2 optical module, CWDM XENPAK optical module and CWDM LX-4 optical module.
In addition, for 10G optical transceiver, CWDM optical module includes CWDM SFP+ optical transceiver, CWDM XFP optical module, CWDM X2 optical module, CWDM XENPAK optical module, CWDM LX-4 optical module. IEEE Association defines an CWDM application standard for designs of equipments with high rate, namely IEEE 802.3 AE-2002. After that, CWDM 10G optical module can achieve longer transmission distance at 10Gbps. But even so, with the advent of QSFP28 100G CWDM4 for 2km transmission,  CWDM 10G optical modules can be not be spoiled as before.

Advantages& Applications of CWDM Optical Transceiver
A detailed  introduction to types and standards of CWDM optical transceiver is made in the above contents. However, what are the advantages of CWDM optics? The answer is as follows:
1. Data transmission transparency
2. Large capacity, making full use of the bandwidth resources of the optical fiber.
3. CWDM technology greatly saves fiber resources and effectively reduces construction costs
4. It has the flexibility, stability and reliability of networking.
5. It can be compatible with all optical network switching to achieve long-distance and without relay transmission.
6. The simplification of the laser module reduces the volume of the equipment and greatly saves the space of data center.
7. The optical layer recovery is with independency and can effectively protect the data transmission.
8. Low insertion loss and low polarization correlation loss.
Surely, with so many advantages, the applications of CWDM optical modules cover a wide fields, such as in CATV (cable TV), FTTH (FTTH), 1G and 2G fibre channel, fast and Gigabit Ethernet, synchronous optical network SONET OC-3 (155Mbps), OC-12 (622Mbps) and OC-48 (2.488Gbps), the field of security and protection system.

Summary
Above all is an introduction to CWDM optical transceiver. Hoping it will be beneficial to your applications in the future life. Furthermore, if you want to know more information about the above mentioned CWDM optical transceivers, you can get them at Gigalight.

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 :

• It is accorded to the standardized applications
• 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.
• Its overall price is one of the most cost-effective options at present.
• 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.

Summary
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.

What Are the Differences Between CXP and CFP Optical Transceivers?

With the rapid development of technologies, 100G Ethernet starts to prevail in people’s daily life, in which interfaces for 100G active equipments include CFP and CXP optical transceiver. However, how much do you know about CFP and CXP optics? And what are the differences between CFP and CXP optical transceiver? Gigalight will tell you the answers in this post.

An Introduction to CXP Optical Transceiver
CXP optical transceiver is targeted at the clustering and high-speed computing markets, thus CXP optical transceiver is usually called as high-density CXP optics. Technically, the CFP will work with multimode fiber for short-reach applications, but it is not really optimized in size for the multimode fiber market, mostly due to that high interface density is required in the multimode fiber market. The CXP is created to satisfy the requirements of the data center for high density, targeting parallel interconnections for 12x QDR InfiniBand (120Gbps), 100GbE, as well as all links between systems collocated in the same facility. The InfiniBand Trade Association is currently standardizing the CXP.

The CXP is 45mm in length and 27mm in width, slightly larger than an XFP. It consists of 12 transmitting and 12 receiving channels in its compact form factor, which is achieved via a connector configuration similar to that of the CFP. Besides, the CXP enables a front panel density that is greater than that of an SFP+ running at 10Gbps. And its transmission distance can reach up to 100ms.


An Introduction to CFP Optical Transceivers
CFP, short for C Form-factor Pluggable, is designed after the Small Form-factor Pluggable transceiver (SFP) interface, but is significantly larger to support 100Gbps.The C stands for the Latin letter C used to express the number 100 (centum), on account that the standard is primarily developed for 100 Gigabit Ethernet systems. In fact, CFP also supports the 40GbE. When it comes into CFP optics, CFP is always defined as multipurpose CFP.

The CFP form factor(including three form factors: CFP, CFP2, CFP4, shown as the pic), as detailed in the MSA, supports both single-mode and multi-mode fiber and a variety of data rates, protocols, and link lengths, including all the physical media-dependent (PMD) interfaces in the IEEE 802.3ba standard. At 40GE, target optical interfaces include the 40GBase-SR4 for 100 meters (m) and the 40GBase-LR4 for 10 kilometers (km).  Simultaneously, there are three PMDs for 100GE: 100GBase-SR10 for 100ms, 100GBase-LR4 for 10kms, and 100GBase-ER4 for 40kms. Moreover, 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.





CFP vs. CXP Optical Transceiver：What Are the Differences?
When it comes to the differences between CFP and CXP optic transceiver module, it seems that the similarities of  them are more than differences of them. Thus, the similarities will be firstly introduced before the differences are involved in. In terms of form factors, both of CFP and CXP optical transceiver are hot pluggable. In the aspect of design, both are with transmitting and receiving functions. With respect to data rate, both support data rates of 40Gbps and 100Gbps. Although CFP is similar to CXP in acronym and the time of emerging, and the form factor of CFP and CXP optical transceiver is markedly different in size, density, and application. The differences in the density and size actually shown in the separate introductions to CFP and CXP. Therefore, the next content will mainly focused on the introduction of the difference in applications.

In applications, the CFP supports both single-mode and multimode fiber and can accommodate a host of data rates, protocols, and link lengths, primarily aimed at 40G and 100G Ethernet applications. While the CXP, by contrast, is targeted at the clustering and high-speed computing markets. Furthermore, CFP is for long-reach applications, while CXP is for short-reach applications. Thus, the existence of CXP does not mean the replacing of CFP.


Summary
To sum up, there are many similarities and differences between CFP and CXP optical transceivers. In some sense, there is a competition between CFP optical transceivers and CXP optical transceivers, which is due to that CFP optics can also be used with multimode optic fibres. Well, the actual applications depend on the users' choices. For example, if one needs to build a network available for various data speeds, CFP optical transceiver can be used; if it is mainly used for short-distance transmission, the CXP optical transceiver will be a better choice. For above mentioned products, more details are at infiberone.com.

Do You Know These Tips about CFP Optical Transceivers?

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.

Conclusion
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 ).





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.

Summary
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.

Do You Really Know 100G Optical Transceiver?

With the rapid development of big data market, the consructions of backbone, interface network and data center need to purchase plenty of optical interconnect products to bring brand new market chance. Nowadays, 40&100G optical transceivers have been developed into the mainstream of markets. Then this article will mainly come into 100G optical transceivers from the perspectives of the development background, types & standards, and the challenges.

1. Background of 100G Optical Transceivers
With the development of tech, optical communication products are widely applied in the daily life. Simultaneously, the demands on the network tech are also increased with it. Therefore, 100G optical transceiver modules gradually appear in the market. The earliest one type of 100G optical transceiver emerged in the form factor of CFP in 2010.At that time, IEEE realized three standards(SR10, LR4 and ER4) for 100G optical modules, respectively focusing on the 100ms, 10kms and 40kms transmission. Then the IEEE standard added new 100G SR4 project, but in 2013 it did not reach consensus. In 2016, the 100G optical transceiver modules for various data centers mostly adopted the 25Gbps Serdes program. After that, the 100G optical modules that use the 50Gbps Serdes plan slowly appeared.

2. Types & Standards of 100G Optics

1). Types of 100G Optical Transceiver Module
At first, a quick review on the 40G optical transceiver will be made. QSFP+ is the only form factor for 40G while the situation is quite different to 100G. Actually, 100G optical transceivers have a bunch of form factors like CFP/CFP2/CFP4, CXP, and QSFP28, the letter “C” is an abbreviation of “centum,” and “Q” means “Quad.” CFP4 and QSFP28 are the latest form factors for the 100G optical transceiver, in fact, QSFP28 has recently become the most popular form factor by now. QSFP28 is an industry format jointly developed and supported by many network component vendors, reaches the data rate of 4x28Gbps.

2). Standards of 100G Optical Transceiver Module
In addition to the IEEE standards, there are also some standards used to define 100GE transceivers, such as Parallel Single-Mode (PSM4) and Coarse Wavelength Division Multiplexing (CWDM4) developed by MSA industry groups.
The 100G PSM4 specification meets the requirement for a point-to-point 100Gbps link over eight single mode fibers up to at least 500m. Four identical and independent lanes are used for each signal direction. It provides a low-cost solution for long-reach data center optical interconnection and aims at the service that needs a parallel single mode module.

100G QSFP28 CWDM4 has many advantages, such as low power consumption, high compatibility, Digital Diagnostic Monitoring (DDM) support and so on. Nowadays, it has been widely applied to Local Area Network (LAN,) Wide Area Network (WAN,) Ethernet switches, and router application.

3. Challenges of 100G Optical Modules

• Channel Distance: The DWDM system supporting the 50GHz wavelength distance is very extensive. The 100G optical module needs to be satisfied with the condition of supporting the 50GHz wavelength distance, therefore, the pattern of high spectral power should be used.
• OSNR (Optical Signal-to-Noise Ratio): Under the same pattern, 100G optical module requires 10dB higher than 10G optical module and 4dB higher than 40G optical modules. Therefore, a low OSNR tolerance code and high coding gain FEC algorithm.
• CD margin: Under the same conditions, the dispersion tolerance for 100G optical modules is 1/100 of 10G optical modules, accounting for 40G optical module 16/100. It can use dispersion compensation technology, in the electric field or the optical domain compensation to complete the dispersion compensation for each wavelength.
• PMD tolerance: Under the same conditions, PMD (polarization mode dispersion) tolerance of 100G optical modules is 1/10 of 10G optical module, accounting for 4/10 of 40G optical module, so you need to choose coherent reception and digital signal processing.
• Non-linear effects: 100G optical module than 10G / 40G optical module nonlinear effects more messy.

4. Summary
Although 100G optical transceivers is faced with so many challenges, and they will get overcome with the advancement of future techs. Believing 100G optics will still prevail for a long time. For this, Gigalight, as a professional supplier of optical components, have launched a series of 100G optical transceiver modules to keep pace with the development trend of optical interconnect markets. Welcome to contact 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:

• CFP – Currently at standard revision 1.4 and is widely available in the market
• CFP2 – Currently at draft revision 0.3, half the size of the CFP transceiver; recently available in the market
• 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.

Summary
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

The Differences Between Singlemode and Multimode QSFP28

After the evolution of optical network from 10G-40G-100G, 100G optical transceivers emerge, including 100G CFP, CFP2, CFP4, CXP and QSFP28. The most outstanding one type among these 100G transceivers is QSFP28 optical transceiver, which prevails in the optical interconnect industry by virtue its high speed, low in power consumption and cost, high density port, longer transmission distance, etc. Optics usually can be divided into single-mode/multimode optical transceiver. Then this post will make an analyses to QSFP28 optical transceiver from perspectives of single mode and multimode.

A Brief Introduction to Singlemode QSFP28 Optics
It’s known that single mode fiber is small in size of core and narrow in laser wavelength. It is due to it that single mode fiber is available for signal transmission with higher bandwidth to realize data transmission at longer distance. Single-mode QSFP28 usually adopts single mode fiber, mainly works at 1310nm wavelength and for longer distance transmission. Different types of single mode QSFP28 can achieve different data transmission distances, such as 100GBASE-PSM4 QSFP28 available for 500 meters, 100GBASE-CWDM4 QSFP28 available for 2 kilometers and 100GBASE-LR4 QSFP28 available for 10 kilometers. Simultaneously, there still exits some other differences among them, shown as the below table:

	connector interface	cable
100GBASE-PSM4 QSFP28	12-fiber MTP connector interface	MTP cable
100GBASE-CWDM4	duplex LC connector interface	duplex LC patch cable
100GBASE-LR4 QSFP28	duplex LC connector interface	duplex LC patch cable

A Brief Introduction to Multimode QSFP28 Optics
Multimode fiber is bigger in the size of core and wider in the wavelength of light. It is available for connection with inexpensive LED light sources and alignment of the connectors with a coupler less critical than that of single mode fiber. After that, optics transmitting over multimode fiber have a higher capability to gather light from the laser at a lower cost. Multimode QSFP28 usually utilizes the multimode fiber, mostly works at 850mn wavelength. At the same time, it is available for short optical link, such as 70ms over OM3, and 100ms over OM4. Among QSFP28 optics, one belonging to multimode optics is only QSFP28 100GBASE-SR4 with 12-fiber MTP connector interface, connected with MTP cable(shown as the pic).



Singlemode QSFP28 vs. Multimode QSFP28 Optical Transceiver: What Are the Differences?
With respect to the differences between single mode QSFP28 and multimode QSFP28 optics are mainly shown in these aspects:

• Transmission distance: the transmission distances that single mode QSFP28 optical modules can reach include 500 meters, 2 kilometers and 10 kilometers; while transmission distance that multimode QSFP28 optic can achieve is 100 meters.
• Power consumption: multimode QSFP28 consumes less power than singlemode QSFP28, which is an important consideration especially when assessing the cost of powering and cooling in the data center.
• Cost: on account that single-mode fiber optics require more expensive laser sources, the cost of single mode QSFP28 is nearly two or three times higher than that of multimode QSFP28 optic.
• Transmission media: single mode QSFP28 is usually connected with single-mode fiber; while multimode QSFP28 is connected with multimode fiber. It is known that 100GBASE-PSM4 QSFP28 is used with single-mode MTP cable and 100GBASE-SR4 QSFP28 is used with multimode MTP cable; while 100GBASE-CWDM4 QSFP28 and 100GBASE-LR4 QSFP28 are used with single-mode duplex LC patch cable.

Summary
Generally speaking, the difference between single mode QSFP28 and multimode QSFP28 mainly focuses on cost, power consumption, transmission distance, etc. At the same time, the advantages of them are also reflected by comparison. However, as for this question: which one is the best solution for 100G Ethernet? It is up to one’s actual demands.

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 Multiplexing）technology, 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 low‐latency applications.

Why  to Choose CLR4
The motivation for the 100G-CLR4 specification is to provide open, multi‐vendor specification for a cost‐effective, low power, 100Gbps (4x25.78GBd), CWDM optical transceiver with a reach of up to 2km over duplex single‐mode 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:

• Low power-consumption.
• Compact transceiver form factor: The 100G-CLR4 Specification is transceiver form-factor agnostic, with QSFP28 as the initial form factor.
• Compatibility with SMF connectors and cable infrastructure for present and future datacenters,
• as well as telecom client-side interfaces.
• Application supports operation with and without Forward-Error-Correction (FEC):
• Enables use with FEC for increased link margin or operation without FEC for lower
• power consumption and lower latency.
• A variety of opto-electronic implementation approaches and technologies.
• 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.

 
Summary
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.

Comparison of QSFP28 and CFP Optics：Cost, Power Consumption, Port Density

Before the advent of 100G QSFP28 optical transceiver, 100G network is developed in the trend of 10G-40G-100G. However, with the appearance of 100G-Base QSFP28, the development mode tends to be 10G-25G-100G/10G-25G-50G-100G, and begins to prevail in the industry. Simultaneously, some data centers adopting this mode to achieve the upgrade from 10G to 100G.

In the development process of 100G optical transceivers, their  form factor type and standard are developed according to the cost and power consumption, which are regarded as the main drive in the development of interconnect market. QSFP28 is just conformed to these requirements. While compared with CFP similarly belonging to one of 100G optical modules, what is the difference between QSFP28 and CFP？ This article will make a comparison between QSFP28 and CFP series Optics.

What Is QSFP28 Optical 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 100 m. 100GBASE-LR4 QSFP28 can support a much longer distance of 10 km.

What Is CFP Optical Transceiver?
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). The 100G optical interconnect typically means 100GBASE-SR10 in 100 meter MMF, 100GBASE-LR10 and 100GBASE-LR4 in 10km SMF reach, and 100GBASE-ER10 and 100GBASE-ER4 in 40km SMF reach respectively. CFP transceiver is currently defined into two next-generation 100G form factors — CFP2 and CFP4. Compared with the existing CFP, CFP2 and CFP4 will be respectively double and quadruple front panel port density.





CFP Optical Module vs. QSFP28 Optical Transceiver: What Is the Difference？
For their differences, this article will  have an introduction to them in these aspects of cost, power consumption, port density.

Cost: now the data center is mainly 10G network architecture, its interconnect solutions are mainly 10GBASE-SR transceiver and duplex LC multimode patch cord. It will save a lot of time and cost if directly upgrade to 40G/100G network on the basis of the existing 10G network architecture.
Power Consumption: QSFP28 transceiver’s power consumption is usually less than 3.5W, while other 100G transceivers are usually between 6W and 24W. Therefore, QSFP28 transceiver’s power consumption is much lower than others.
Port density: The first generation 100G transceiver is CFP transceiver, having large volume, then is CFP2 and CFP4. CFP4 is the latest generation of 100G transceiver, its width is only 1/4 of CFP transceiver. While QSFP28 transceiver’s package is smaller than CFP4, this means QSFP28 transceiver has a higher port density on the switch.

Summary
Generally speaking, by comparison, QSFP28 optical transceiver is lower in consumption and cost, higher in port density. It bring new solutions for 100G applications to promote the fast development of 100G. The surge of QSFP28 shipments will be one of the factors to change the market from 40G to 100G, according to HIS.

An Overview of DWDM: Definition, Advantages and Applications

When capacity expansion takes place in traditional network transmission, Time Division Multiplexer(TDM) and Space Division Multiplexer(SDM) are adopted. Both of transmission networks use a single wavelength signal for data transmission. However, this transmission method does not make full use of optical fibers with large capacity as transmission medium, resulting in a great waste. To deal with the issue, the DWDM tech comes into optical interconnect markets. Then in this post, an introduction to DWDM will be made in detail.

What Is DWDM?
DWDM, short for Dense Wavelength Division Multiplexing, is a technology that gather datum from different sources on an optical fiber. It’s applied in fiber optical transceiver(so DWDM XFP, DWDM tunable SFP+ and so on appear) to increase bandwidth over existing fiber optic backbones, and is with each signal simultaneously carried on its own separate light wavelength. The “dense” here means that the wavelength channels are very close to each other. Besides, DWDM, up to 80 (and theoretically more)separate wavelengths or channels of data can be multiplexed into a light stream transmitted on a single optical fiber. DWDM systems require complex calculations of balance of power per channel, which is further complicated when channels are added and removed or when it is used in DWDM networks ring, especially when systems incorporate optical amplifiers.





Advantages of DWDM
In terms of tech and economy, the ability to provide potentially unlimited transmission capacity is the most obvious advantage of DWDM technology. The current investment in fiber plant can not only be reserved, but optimized by a factor of at least 32. As demands change, more capacity can be added, either by simple equipment upgrades or by increasing the number of lambdas on the fiber, without expensive upgrades. Capacity can be obtained for the cost of the equipment, and existing fiber plant investment is retained.
Bandwidth aside, the most compelling technical advantages of DWDM can be summarized as follows:

• Transparency: due to that DWDM is with a physical layer architecture, it can transparently support both TDM and data formats such as ATM, Gigabit Ethernet, ESCON, and Fibre Channel with open interfaces over a common physical layer.
• Scalability: DWDM can leverage the abundance of dark fiber in many metropolitan area and enterprise networks to quickly meet demand for capacity on point-to-point links and on spans of existing SONET/SDH rings.
• Dynamic provisioning: fast, simple, and dynamic provisioning of network connections give providers the ability to provide high-bandwidth services in days rather than months.

Applications of DWDM
With so many advantages, DWDM is naturally applied in many situations, then some main applications of DWDM are shown as follows:

1. The distance limitation can be overcome by transporting data between one or more enterprise locations and one or more SANs over the optical layer using DWDM. In addition to overcoming distance limitations, DWDM can also reduce fiber requirements in SANs.
2. DWDM can be used to remove an entire class of equipment, the SONET ADMs. This change, which might constitute a second phase of SONET migration, allows routers and other devices to bypass SONET equipment and interface directly to DWDM, while simplifying traffic from IP/ATM/SONET to POS to eventually IP directly over the optical layer
3. Both ESCON and FICON require a pair of fibers for every channel. By multiplexing these channels over DWDM transport, significant savings can be realized.
4. DWDM has capability to expand capacity and can serve as backup bandwidth without a need to install new fibers, thus it is ready made for long distance telecommunication services.
5. DWDM can also be used in various networks like sensor networks, remote radar networks, tele spectroscopic process control network and many more networks.
6. By the use of only two fibers, 100% protected ring with 16 separate communication signals can be constructed deploying DWDM terminals as these are self healing rings.
7. In order to meet the demand in fast growing industrial base, DWDM system can be used for existing thin fiber plants as these plants cannot support high bit rates.

It’s believed that there are great demands for large transmission capacity in current optical interconnect markets. While large transmission capacity is regarded as its outstanding benefit, it will contributes to the development of DWDM tech to a large extent. Furthermore, as the ideal technology for communication systems, there is no doubt that DWDM technology will reshape the future communication network by virtue of its various advantages and applications in many aspects.