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.
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.