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Infiberone one-stop optical network devices provider
Infiberone one-stop optical network devices provider


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.


How to Choose QSFP28 Optical Transceiver For 100G Network?

It’s known that cost-effective 100G optics are in great demand, especially QSFP28 optical transceivers with low cost optical design package tech, widely applied in data center, LAN, WAN, Ethernet switches. However, among these optic fibre modules, which one is the most suitable for 100G Network? Well, this article will introduce how to choose QSFP28 optical transceivers.

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.
To some degree, the selection of 100G QSFP28 products depends on transmission distance. Therefore, it would be better to choose it from this perspective. For different applications, there are different requirements for transmission distance. The below is about its specific conditions and feasible measures:
  1. When transmission distance is 100m or under 100m, QSFP28 SR4 is highly recommended. The QSFP28 SR4 supports links of 70 m (OM3) and 100m (OM4) over multimode fiber with MPO connectors. It offers 4 independent transmitting and receiving channels, and each is with 25Gbps able to be aggregated into 100Gbps. Meanwhile, the QSFP28 SR4 optic module is also ideal for the connections from rack to rack in the data center. 
  2. When transmission distance is over 100m but under 10 km, QSFP28 LR4 is preferred. The QSFP28 LR4 is a fully integrated 4 × 25Gbit/s optical transceiver module, supporting distance up to 10 km. So for long span 100G deployment, such as cabling between two buildings, QSFP28 LR4 with duplex LC and single-mode fiber cable is the perfect option. 
  3. When transmission distance exceeds 10 km, QSFP28 ER4 is ideal for very long transmission distance. It provides superior performance for 100G Ethernet applications up to 30km links and converts 4 input channels of 25Gb/s electrical data to 4 channels of LAN WDM optical signals and then multiplexes them into a single channel for 100Gb/s optical transmission.
Of course, the above ways are just for the different transmission distance. But for the  same transmission distance, how to choose it? Maybe we can get the answer from the example of QSFP28 CWDM4 and QSFP28 PSM4.

The QSFP28 CWDM4 provides a 100G Ethernet high-speed link with a maximum transmission distance of 2 km, which interfaces with LC duplex connectors, and uses Mux/Demux technologies with 4 lanes of 25Gbps optically multiplexed into and demultiplexed from duplex single-mode fiber. While PSM4 does not need a MUX/DEMUX for each laser but it does need either a directly modulated DFB laser (DML) or an external modulator for each fiber. Besides, with an MTP interface, PSM4 modules can transmit data at 100Gb/s from point to point over 2 km or can be divided into dual 50Gb/s or quad 25Gb/s links for linking to servers, storage and other subsystems.

It’s seen from that both of QSFP28 CWDM4 and QSFP28 PSM4 are designed to meet the requirement for intermediate or mid-reaches for datacenter applications (500 m to 2 km). And they both use WDM and parallel single mode fiber technologies and support transmission distance up to 2 km.

When faced with such a situation, maybe we can make a decision from the two aspects. For one thing, from the aspect of an inner transceiver module structure, by comparison , PSM4 can be more cost-effective due to its lower component costs. For another thing, from the infrastructure viewpoint, PSM4 will be more expensive when the link distance is long, because PSM4 uses 8 optical single-mode fibers while CWDM uses only 2 optical single-mode fibers.

All in all, when choosing one QSFP28 optical transceiver for 100G network, one can take different solutions according to the practical demands in different situations.  The most suitable is the best.

Note: article resource from


How Much Do You Know about BiDi Transceiver?

In today’s data center, higher bandwidth and larger capacity are required, which, to some degree,  brings about the increasing in the use of optic fiber cables. It’s known that two fiber cables are usually used in the process of data transmission, in which one is for transmitting data, and another one is for receiving data. After that, the cost in the fiber deployment of infrastructure is also increased with it. To solve this issue, BiDi transceiverBidirectional transceivercomes out, such as BiDi SFP, BiDi SFP+, BiDi QSFP+ and so on. Then this article will have an introduction to BiDi transceiver.
What’s BiDi Transceiver?
BiDi transceiver is a kind of bidirectional fiber optic transceiver with single fiber, which transmits and receives different central wavelengths from two different directions by WDM tech, to realize bidirectional transmission of optical signal in one optic fiber. Different from common fiber optic transceiver with two ports, BiDi transceiver is only with one port. It filters wavelength via filter and simultaneously complete the transmission of 1310nm optic signal and receiving of 1550nm optical signal so that it need to be applied in pair. Usually, its wavelength consists of these types: 1310nm/1550nm; 1310nm/1490nm; 1510nm/1590nm.
Types of BiDi Transceiver
The common types of BiDi transceivers include the following ones:
1.    BiDi SFP transceiver is typically applied for the high-performance integrated duplex data link on one optic fiber. It interfaces mother board of network device (such as a switch, router or similar device) to a optic fiber or unshielded twisted pair networking cable. In addition, the typical wavelength combination of it is 1310/1490nm, 1310/1550 nm, 1490/1550 nm and 1510/1570 nm. This SFP BiDi transceiver is used in both telecommunication and data bidirectional communications applications.
2.    BiDi SFP+ transceiver is an enhanced SFP transceiver. It is designed for bi-directional 10G serial optical data communications such as IEEE 802.3ae 10GBASE-BX by using 1330/1270nm transmitter and 1270/1330nm receiver. And its transmission distance is up to 20 km.
3.    BiDi QSFP+ transceiver is designed for high-density data center. With QSFP+ BiDi transceiver, 40G network can be achieved by the exiting 10G cabling. That is to say, if one wants to upgrade his 10G network to 40G network, there is no need to change the existing 10G duplex patch cords into MTP/MPO multifiber patch cords.
4.    BiDi X2 transceivers, mainly used in Ethernet network, are designed for bi-directional 10G serial optical data communications, similar to BiDi SFP+ transceivers. The transceiver consists of two sections: the transmitter section and the receiver section. The transmitter section uses a multiple quantum well 1330/1270nm DFB laser. The receiver section uses an integrated 1270/1330nm detector preamplifier (IDP) mounted in an optical header and a limiting post-amplifier IC. This BiDi transceiver is mainly used in Ethernet network.
Advantages of BiDi Transceivers
On the one hand, due to that BiDi transceivers( also called as WDM transceivers) are able to reduce the number of fiber patch panel ports and the amount of tray space for fiber management, as well as to require less fiber cables, the adoption of BiDi transceivers is beneficial to save the cost in fiber cabling infrastructure. Meanwhile, it also makes it possible to save more precious space in data centers.
On the other hand, although the cost of BiDi transceivers are higher than that of common transceivers in the market, and BiDi transceivers utilize half the amount of fiber per unit of distance. For many networks, the saved costs can offset the higher purchase costs of BiDi transceivers. The deployment of BiDi transceivers instantly doubles the bandwidth capacity of the existing optical fiber infrastructure and helps customers to achieve economical and efficient performance for their fiber optic network. Besides, 40G connectivity becomes more reliable via BiDi transceiver.
How Does BiDi Transceiver Work?
Different from traditional optic fiber transceiver modules with two fibers, BiDi transceivers are equipped with Wavelength Division Multiplexing (WDM) couplers, also called as diplexers, which combine and separate data transmitted over a single fiber according to  the wavelengths efficiency. On account of this, BiDi transceivers are also referred to as WDM transceivers.
Furthermore, BiDi transceivers must be deployed in pairs to reach the efficiency, with their diplexers tuned to match the expected wavelength of the transmitter and receiver. For example, paired BiDi transceivers are used to connect device A (Upstream) and device B (Downstream), then the figures are shown as below:
1.     Transceiver A’s diplexer must have a receiving wavelength of 1490nm and a transmit wavelength of 1310nm
2.     Transceiver B’s diplexer must have a receiving wavelength of 1310nm and a transmit wavelength of 1490nm

BiDi Transceiver

BiDi transceiver may have a higher cost than common transceivers. However, if seen from a long-term view, it will decrease the costs spent in fiber cables to a large extent. BiDi transceiver is compatible with many data rates.

Note: article resource from


Advantages and Disadvantages of Optical Fiber Communication

Nowadays, optical fiber communication stands out in the optical communication industry to be the mainstay of modern communication. As an emerging tech, the development pace of optical fiber communication and wide range of applications are unprecedented in the communication industry. However, what does it make so? What are advantages and disadvantages of optical fiber communication? Well, we will get the answer from this article.

optical fiber communication

In modern communication network, there are three pillars: optic fiber communication, satellite communication, and radio communication, in which optic fiber communication is regarded as the principal sector of them. It’s due to that it has various outstanding benefits.
Advantages of Optical Fiber Communication
1.    With Higher Bandwidth and Large Communication Capacity
The available bandwidth for fiber is about 50000GHz. 1.7Gb/s optic fiber communication system adopted in 1987, in which a pair of fibers can simultaneously transmit 24192 channels of telephones; 2.4Gb/s system can transmit 30000 channels of telephones. Bandwidth plays a key role in transmitting various kinds of broadband information. Otherwise, it will not meet the needs of future Broadband Integrated Services Digital Network (B-ISDN)
2.    With Low Loss and Long transmission distance without Repeater
the loss of fiber is very low. When optic wavelength is about 1.55μm, the loss of silica fiber is lower than 0.2dB/km, which is lower than any transmission media. So the transmission distance without repeater can reach to tens of or hundreds of miles. On account of the low loss of fiber, the long-distance transmission without repeater can be achieved. In the optical fiber communication system consisting of silica fibers, the transmission distance without repeater can reach to over 2000km
3.    Anti-Electromagnetic Interference
Optic fiber belongs to insulator material, not interfered by thunder, variation of the ionosphere, sunspot activity; as well as not interfered by industrial equipments, such as electrified railway wires, high voltage devices and so on. It can also be made into the compound cables with electric conductors.
4.    No Crosstalk Interference and With Security
Transmitted in the optic fiber cable, optical wave is hard to leak out. Even if it’s in the turning and its bending radius is very short, the optical wave leaking out from the cable is also weak. If it’s coated with a layer of delustrant on the surface of fiber or  optic fiber cables,  the effect will be better. After that, even though there are many fibers in the fiber cables, it’s able to reach the effect that no crosstalk interference happens and the information transmitted in the fibers is not be intercepted out of optical fibers.
5.    Light in Weight and Short in Diameter
The fiber diameter of optic fiber is very short, 0.1mm, only 1% the one of single-tube coaxial cables. In addition, the diameter of optic fiber cable is also short. The cross-sectional diameter of optic fiber cable with 8 fibers is 10mm; while the one of standard coaxial cable is 47mm. By making use of this advantage, the space of transmission system can be narrowed so that a matter of crowding underground pipes can be solved and the costs for constructing pipes are also saved. Moreover, the fiber cables are lighter than cables in weight. To some degree, it’s easier to produce and install.
6.    Abundant in the Raw Materials of Optic Fiber
The main material of optic fiber is quartz, which is unlimited on the earth; while cable is made of copper, which is limited. If the fiber cable is in replace of cable, amounts of metal materials are able to be saved.
In addition, there are still other strengths, such as with high corrosion resistance, nuclear radiation resistance,  low resource consumption and so on.
Of course, there is no perfect things in the world. No matter how perfect one thing is, it still has its demerits. Optical fiber communication is without exception. The below is about its introduction.

Disadvantages of Optical Fiber Communication
Compared with the merits, the demerits are relatively less, as below:
l  With fragile material and poor mechanical strength
l  The bending radium of optic fiber cable can not be too short>20cm).
l  Separation and coupling are not flexible
l  Requiring more protection around the fiber cable compared with copper cable

Obviously, advantages of optical fiber communication in various aspects contribute to the rapid development of optical fiber communication. Although it’s still with some disadvantages, and it will be improved with the future development of tech. Let’s expect it together.


CWDM vs. DWDM:What Are the Differences?

It’s known that WDM(Wavelength Division Multiplexing) is divided into DWDM(Dense Wavelength Division Multiplexing) and CWDM(Coarse Wavelength Division Multiplexing). With respect to these two types, there is no doubt that DWDM(Dense Wavelength Division Multiplexing) is the first choice in the fiber applications field. However, due to its high price, manufacturers who are lack of finances are hesitant to purchase it. At this time, most of them prefer to choose CWDM with lower cost. As for difference between DWDM and CWDM, it’s far more than this. Today, this article will make an introduction in a way of CWDM vs. DWDM by Gigalight.

1.    What Is CWDM
CWDM is a wavelength multiplexing technology for city and access networks. Transmission is realized using 18 channels with wavelengths between 1270 nm and 1610 nm. Due to the channel spacing of 20 nm cost-effective lasers can be used. The channel width itself is 13 nm. The remaining 7 nm is designed to secure the space to the next channel. Moreover, CWDM is very simple in terms of network design, implementation, and operation. CWDM works with few parameters that need optimization by the user.

CWDM highlights
l  Up to 18 CWDM wavelength over one pair of fiber
l  CWDM channel spacing 20 nm, 1270 nm to 1610 nm
l  Distances up to 120 km
l  Cost-effective WDM solution
l  Scalable by hybrid CWDM/DWDM - perfect solution for your investment

2.    What Is DWDM
DWDM is a technology that puts data from different sources together on an optical fiber, used in fiber optics to increase bandwidth over existing fiber optic backbones, and is with each signal carried at the same time 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 lightstream 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.
DWDM highlights
l  Up to 96 DWDM wavelength over one pair of fiber
l  DWDM channel spacing 0.8 nm (100 GHz grid) or 0.4 nm (50 GHz grid)
l  Distances over 1,000 km can be achieved with the use of optical amplifier
l  DWDM wavelength: 1528 nm (channel 61) to 1563 nm (channel 17)
Seen from the brief  introductions of CWDM and DWDM, they distinguish in wavelength spacing, transmission distance. Well, actually, they also  differ in cost, optic modulation, power requirements and so on. The following content will be involved in CWDM and DWDM comparison from perspectives of wavelength spacing, transmission distance, cost, optic modulation, power requirements one by one.


3.    CWDM vs. DWDM: Which One Is Better?
In wavelength spacing, CWDM supports up to 18 wavelength channels transmitted through a fiber at the same time. To achieve this, the different wavelengths of each channel are 20nm apart. DWDM, supports up to 80 simultaneous wavelength channels, with each of the channels only 0.8nm apart. CWDM technology offers a convenient and cost-efficient solution for shorter distances of up to 70 kilometers. For distances between 40 and 70 kilometers, CWDM tends to be limited to supporting eight channels. Unlike CWDM, DWDM connections can be amplified and can therefore be used for transmitting data much longer distances.
In transmission distance, DWDM is available for a longer distance transmission by keeping the wavelengths tightly packed. It can transmit more datum over a larger run of cable with less interference than CWDM system. CWDM system cannot transmit data over long distance as the wavelengths are not amplified. Usually, CWDM can transmit data up to 100 miles (160km).
In cost, the DWDM cost is higher than CWDM cost. Due to the uneven distribution of temperature in wide optical wavelength range, and temperature is hard to be tuned, which results in the high cost. While CWDM can make it so that the cost of CWDM is reduced in a large scale, which is now 30% of DWDM cost.
In optic modulation, they are different from each other. The optic modulation of CWDM adopts the electronic tuning instead of non-cooled laser. However, on the contrary, the optic modulation of DWDM adopts the cooled laser and utilizes the temperature for tuning.
In the power requirements, DWDM has significantly higher power requirements than CWDM. For example, DWDM lasers are temperature-stabilized with peltier coolers integrated into their module package. The cooler  with associated monitor and control circuitry consumes around 4W per wavelength. Meanwhile, an uncooled CWDM laser transmitter uses about 0.5W of power.
4.    Conclusion
By the CWDM and DWDM comparison, the difference between CWDM and DWDM is apparent. Although they respectively have their own unique advantages, and it seems that CWDM will be more attractive for carriers who need to upgrade their networks to accommodate current or future traffic needs while minimizing the use of valuable fiber strands, on account that CWDM’s ability to accommodate Ethernet on a single fiber enables converged circuit networks at the edge, and at high demand access sites. Of course, if out of consideration of bandwidth and transmission distance, DWDM is also a good choice. In a word, it’s up to one’s specific demands.


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Gigalight Tech Center Address In Wuhan


Gigalight 100G Single Optical Transceiver Has Been Admitted By Domestic DPI Manufacturers

Nowadays, DPI industry is developed rapidly. In the development waves, the demand of Network security is constantly raised, and the personalized recognition for the users’ service is also gradually strengthened. Therefore, how to meet the market demands of data center, manufacturers and Internet enterprises,has recently become the crucial topic of Gigalight.
However, at the process of the implement from the gradual upgrading of 10G POS/WAN-40G/100G to the enrichment of product line, the improvement of delivery capability, the making of long-term goals, Gigalight has made breakthrough achievements in these aspects, seen from the truth that Gigalight continuously has won the bids  of the leading DPI device manufacturers in this field and has gained their supports. Now, the below is the detailed introduction about these measures:

Measure 1: Providing Rich Product Lines
For an enterprise, products are the core. Rich product lines is able to meet the needs of manufacturers in many aspects and to reduce the combination costs. Therefore, Gigalight spares no effort to build one rich product line, 100G QSFP28 LR4/CFP LR4/CFP2 LR4 series single optical module product line, satisfying the needs of clients about the high bandwidth. Meanwhile, by the tech innovation , the adoption of self-developed ROSA components lead to the low-cost products, bringing DPI manufacturers practical benefits. In addition, the 100G CFP4 LR4 also can be customized and achieve the multiple options of products.

Measure 2: Improving the Delivery Capability
For the professional optical transceiver manufacturers, they are not only with the ability to offer clients high-quality and high-performance optical transceiver solutions, but also with the delivery capability to share the delivery pressure of manufacturers.

Recently, Gigalight DPI series 100G single optical transceiver continuously won the bids of leading device manufacturers. Faced with the short delivery time, Gigalight gave the manufacturers a satisfying result by virtue of their strong delivery ability and high quality products, by which they are highly admitted by domestic DPI manufacturers and DPI market is also injected a new fresh air. 

Measure 3: Making The Long-Term Goals
For a company, a long-term  goal is the motivation of producing and the soul of offering higher-quality service for clients. Gigalight combines the market needs and its own tech strengths to achieve the goal, in the later two years’ DPI market, making the 100G product’s cost at $100 via scale and new tech to get the DPI devices applied widely, to continuously provide manufacturers with high-quality and low-cost optical module products and to offer more low-cost products to DPI manufacturers for options.

Above all is the Gigalight news about 100G single optical transceiver. If you want to know more, welcome to contact us at any time.

Note: Gigalight is the head office of Infiberone.


Consideration on the Applications of 100GE QSFP28 in the Large-Scare Data Center

1.The Changes On the Structure of Data Supercomputing Center Lead to the 100GE ports’ rapid increasing in Number, Showing the importance of Structure 
With the rapid increasing of IP flux , the accelerated infiltration of cloud computing and virtualization, and the fast burstout of IDC inner flux, large-scale data center is developed toward new and flat leaf- spine network structure continuously. Traditional three-layers network structure of data center will be replaced by new and flat leaf- spine network structure. 

Meanwhile, With the rapid increasing in quantity of interconnection ports between leaf converters and spine converters, the demands on high-end 40GE/100GE optical transceiver also rise rapidly with it. It’s predicted by the Third-Part Institution that 40GE/100GE high-speed optical modules’ quantity ,needed by leaf- spine network structure, is 15-30 times the quantity of Traditional three-layers network structure for the large-scale data center. In addition, high-speed optical modules will be upgraded from10G/40G optical module to 100G/200G, especially is 100G optical module, demands for it will be raised in a large scale. 

2.Exploration On the Background of Rapid Increasing for 100G Optical Module, Showing the Importance of Wiring 
It’s predicted by the Third-Part Institution, Ovum, that the deployed quantity of 100G single-mode optical module will be close to or exceed the one of 100G multimode optical module, With the rapid increasing in quantity of interconnection ports between leaf converters and spine converters, and the distance among converters extended . Shown as the above pic, in the data center with 500,000 ft2, the quantity of TOR/Leaf/Spine converters and 100G single-mode/multimode optical modules has been listed clearly. We need to make some theoretical exploration:  

A. Difficulties in wiring space due to the density of scales and devices. For these difficulties, data center may prefer to choose the 100G CWDM4 optical module in the long-distance interconnection, because it saves the fiber wiring space and the reduces fiber wiring difficulties superficially at least. But such kind of savings lead to self-limitation on account that wiring structure has no good designs from the beginning. Therefore, deep consideration is necessary before deploying it.

B. Based on the comprehension for scale and different techs, PSM4 and CWDM4 optical module will be deployed. They should be used on the basis of comprehensive assessment for their stability, power dissipation and working life. Technically evaluating, CWDM4 optical module is more complicated than PSM4 optical module. 

But whether the complex standards constituted by industry association are reasonable is worth reflecting. The performance of CWDM4 optical module is becoming higher and higher, and the large-scale usage for it will exist no dangers under the guarantee of 65 or double-85 test’s reliability. But we haven’t seen the improvements on techs from PSM4 to CWDM4, and it seems that everything is like factitious tech barriers and trends. Our viewpoints on CWDM4 are that it’s just an extension for PSM4 optical module, not another application tech superior to the former. The large-scale applications for the PSM4 and CWDM4 may be a miracle in the data center.

C. The wiring structure of data center has a great influence in the cost of large-scale data center. What we should focus on is wiring, not devices, which we consider as the deviation of industry’s focus. When we are keen on studying converters and servers with high speed and high performance, we must have wiring techs suitable for them, which is just like that inspection for subgrade , the assurance for the structure and plot ratio of the building, should be done before building a house. If everything about it weren’t confirmed, the built house may be with hidden safety dangers or not good in Fengshui theory. 

Similarly, if we don’t confirm the basic wiring, the PCB layout of electrical products, in advance, the performance of them will be at a mess. If a data center is built hastily, no differences with previously-built computer room, and it will truly enter into the deserted stage. 

D. We must have a long-term consideration on data center, in which long term must be a relative concept. How long it should be must integrate the present progress and demands on dealing with the datas in the data center. If the sources of rapid increasing needs aren’t confirmed, frankly speaking, the distribution for a new data center will be finally proved to be impractical and wasteful when it adopts immatural or the most advanced products. 

In addition, the future level about interconnection tech of data center still isn’t confirmed, even though certain paths made by industry association aren’t necessarily correct in the direction. Now, industry association is used to making many decisions hastily, which usually leads to efforts in the incorrect direction. 

3.Advantages of 100G PSM4/100G CWDM4/100G LR4 Optical Module And The Importance of Choices.
A comparison about the integrated parameters of 100G optical module in wavelength, optical connector, fiber types, working distance, the interior of optical module with/without MUX/DEMUX, system terminal with/without needs of FEC function, the power dissipation of optical module and so on, in this table, used for customers’ reference:    

100GBASE-SR4(100 m) and 100GBASE-LR4(10 km) are defined by IEEE. Due to the needs from data center customers, 100G CWDM4 and 100G PSM4 are also defined by MSA, making up for the gap in needs between 100meters and 10KM. Compared with 100GBASE-LR4, 100G CWDM4 and 100G PSM4 have the lower cost advantages and their application distances cover 2 KM. And 100G PSM4 adopts parallel single-mode tech and MPO APC 8°connector with eight fibers, with the lowest cost in the 100G single-mode transmission tech. 

Besides, in the market, there is 100G PSM4 made on the basis of silicon photonics tech or traditional 4x mini TOSA packaging tech. Similarly, they have the advantages on the low cost. Sometimes two-fibers CWDM4 are considered to be more economical and practical than multi-fibers PSM4. However, the results is contrary:
1. PSM4 increases the complexity of wiring density, and CWDM4 results in the complexity of devices’ performance. 

2. PSM4 is still available to extend in space, and CWDM4 has gotten into the endless loop.

3. PSM4 is with higher stability and reliability in the wavelength, and in the present whole chain, CWDM4 still exists problems in reliability and have no way to pass the double-85 test. 

4. PSM4 is with lower power dissipation, and CWDM4 needs interior temperature or control from the external environment to reach the ideal power dissipation on account that the narrow space of module causes the heat dissipation problem.

5. PSM4 is easier to manage because of its clear link path, and CWDM4’s link path is not clear. 

Whatever optic product manufacturers of data center want, the producers of optical module can provide it for them. And it’s proved that there exists direction problems in the previous comparison of advancement and superiority between optical module/ devices and data center. All techs about optical module will tend to be same in the performance and be more stable one year later. We should concentrate on the improvement of wiring techs and more economical and practical items. 

With the progress in the optical interconnection tech, data center will tends to be at the state of instant evolution and flourish, which means continuous devotion and evolution and is with no ultimate products. The combination process from 1G to 100G and then from 400G to 1T, will be the final and vital formation of data center, based on the combination of different applications.  

4.Introduction about 100GE QSFP28 Data Center Application Cases
1. In June, 2016, Azure data center started to adopt Intel 100G QSFP28 PSM4 silicon photonics optical module volumely. Azure cloud service have been used in the 140 countries, and over 90% of Fortune 500 enterprises have applied Microsoft Azure, which will be immediately expanded to 34 areas on the basis of existing 28 areas in the world where more than 100 data centers were invested to build. The number will exceed the sum of AWS, Google and AliCloud. 

2. In February, 2017, Facebook specially released OCP CWDM4 standards to deploy 100G QSFP28 CWDM4 scalely. For the volume production and low cost, Facebook has loosened part of standards, such as working temperature, optical emission power, receiving sensitivity and optical link path index. At present, Facebook has purchased 100G QSFP28 CWDM4 optical module.

5.Recommendation on the Infiberone 100GE QSFP28 Products 
By their own strength, Infiberone developed 100G QSFP28 CWDM4 optical module with cost benefit by themself. This optical module adopts self-packaged optical engine, and some micro components are assembled inside, such as DFB laser(1271nm,1291nm,1311nm and 1331nm)of 4-channels 25Gbps uncooled CWDM, 4-channels optical detector, CDRs, micro AWG chip and so on. Under the total air temperature(0~70℃), its typical power consumption is lower than 2.6W, and its optic eye diagram margin is higher than 20%. 

In addition, its sensitivity is(pre-FEC 1E-5BER OMA)<-10.5dBm. Its error rate guarantees BER is higher than 1x10-12 under the application of post FEC. Meanwhile, it uses Duplex LC optical interface and meets the needs of 2km transmission distance. Infiberone will get about to producing it volumely in the forth quarter of 2017.
Infiberone QSFP28 PSM4 optical module shows a good performance under the  -5°C/25°C /55°C. The uniformity and consistency of four channels are accorded with design requirements and its optical eye diagram margin is higher than 15% under the -5°C/25°C /55°C . and sensitivity is higher than-9.5dbm(1E-5) constrained by agreements, meeting the needs of data center applications in the fiber transmission distance, no less than 2km. the success on the development of Infiberone 100G PSM4 optical module, means that it officially has its own essential tech and skill in the single-mode optical engine. In addition, it will start to produce this product volumely in the third quarter of 2017.

Infiberone set about to developing data center single-mode product line and its packaging techs in 2015 and officially sold 100G QSFP28 LR4 (DML)products in the end of 2016. 100G QSFP28 LR4 optical module’s power consumption is lower than 3.5W, and uses self-packaged optical engine, ROSA. In addition, its transmission distance can reach 10km when it’s connected with single-mode fiber. It conforms to IEEE802.3ba 100GBASE-LR4 and QSFP+ MSA standards. Its typical power consumption is lower than 2.6w under the total air temperature (0~70℃) and its optical eye diagram margin is higher than 20%. In the first quarter of 2017, Infiberone gets down to producing this product volumely.

For Infiberone second-generation 100G QSFP28 SR4 with lower power consumption, under the CDR working condition, its typical power consumption under the indoor temperature and 70℃ respectively is 2W and 2.2W, reaching the power consumption level ,MAX POWER 2.5W in the SFF-8436 V4.8 MSA Power level 3. 

Meanwhile, it meets the standards, such as IEEE 802.3bm 100GBASE SR4, InfiniBand EDR, 32GFC and so on, downward compatible with 10GE, completely suitable for transmission applications on transmission, such as OM3 75meters fiber transmission and OM4 100meters fiber transmission. Under the true test conditions, OM4 fiber with 100meters transmission distance has no any error code according to the stricter error rate test standards. 100G QSFP28 SR4 adopts the lens tech and optical engine tech self-developed by Infiberone, supporting the digital diagnostic function and integrating data channel of 25Gbps with 4 channels and receiving-and-sending function. 

In addition, 100G QSFP28 SR4 optical module is with higher performance in optical eye diagram, sensitivity for receiving and electric eye chattering. At present, this product has been produced volumely. The VCSEL optical module tech and production tech platform are self-developed by Infiberone, and their related cost is close to critical value by optimization whether it’s in coaxial packaging or COB tech. Advantages on the scale of delivering has been strongly supported by suppliers. 

Infiberone is the advocator of 100G QSFP28 optical module products and tech marketing in date center ,and maintains a keen insight into technology and cost . In 2016, Infiberone started to arrange the layout about all series of 100G QSFP28 optical module and solutions. In March,2017, 100G PSM4 optical module was officially pushed out. And in July,2017, the sample of 100G QSFP28 CWDM4 optical module was developed, which used AAWG chip and unique COB tech platform, with good stability in temperature, suitable for the capacity expansion of data center with parallel structure or optical interconnection structure of wavelength division multiplexing style data center. 

The successful development of 100G QSFP28 CWDM4 and 100G QSFP28 PSM4 optical module has built a new competitive strength for Infiberone data center market strategy, and will also be one of the most powerful suppliers of 100G optical module in the domestic data center.

Note: Infiberone is a sub-brand of Gigalight, we focus on high-end optical network devices, mainly supplying industrial-grade optical transceivers and professional optical interconnection components for data centers. With more than 10 years' experience in optics industry, we now have professional R&D team(more than 100 engineers) and stable supply ability.