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For most data centers and network service providers, if they want to remain competitive, they must upgrade their network to higher speed to deliver operational services. In the past years, we talked more about 10G and 40G. Now, the time of 100G is coming according to the latest researches from HIS. It predicts that the service providers expect their 100G ports to be 38% in 2018. There are many ways to transfer the network to 100G with various switches and standards being published, among which 100G QSFP28 modules are considered to be the preferred choice. This post will offer a specific introduction for 100G QSFP28 fiber optic transceivers.
Basic of 100G QSFP28
We know that 40G QSFP+ module uses four 10G lanes for 40G dual way transmission. 100Gbase QSFP28 module has the same package form factor and transmission lane number as QSFP+. But it can support up to 28G per lane. QSFP28 fiber optic transceiver is designed to transmit 100G optical signals over four 28G lanes. Compared with 100Gbase CFP modules, 100G QSFP28 has higher density, which is becoming increasingly popular in 100G market.
Choices for 100G QSFP28 Modules
The QSFP28 module was first invented in 2013. With years of developing, there are various 100G QSFP28 modules that can support different standards and applications.
100Gbase-SR4 QSFP28
As most data centers rely largely on multimode fibers, IEEE standard for 100G QSFP28 that supports short distance over multimode was firstly published, which is 100GBase-SR4. QSFP-100G-SR4 module can support 100G transmission up to 70m over OM3 and 100m over OM4. The 100Gbase-SR4 QSFP28 module achieves four lanes of 25G dual way transmission over eight fibers. Thus, it has an MTP interface.
100Gbase-LR4 QSFP28
For long distance transmission, the IEEE standard 100Gbase-LR4 is being used in QSFP28 module which is known as QSFP-100G-LR4 module. Unlike QSFP-100G-SR4 modules, QSFP-100G-LR4 uses the WDM technologies for four 25G lanes transmission. The four 25G optical signals are being transmitted over four different wavelengths. It has a duplex LC interface for 100G dual-way transmission. 100Gbase-LR4 QSFP28 can support transmission up to 10km over single-mode fiber.
100Gbase-PSM4 QSFP28
Requirements for different applications are various, thus, other standards are being published by the MSA. As 100Gbase-LR4 QSFP28, which can support transmission distance of 10km, overkills many applications. And the modules are expensive. 100Gbase-PSM4 QSFP28 is being designed to support a transmission distance up to 500m over single-mode multi-fibers. It has an MTP interface.
100Gbase-CWDM4 QSFP28
Another module is also designed to meet the different distance requirements. MSA published 100Gbase-CWDM4 standard for QSFP28 over single-mode up to 2km over through duplex LC interface. It also uses WDM technologies like 100Gbase-LR4. But the transmission distance is shorter and the cost is much lower.
QSFP28 DAC
Except the above mentioned commonly used QSFP28 fiber optic transceivers, QSFP28 DAC are also being provided in the market to further decrease the costing of 100G connections over short distance. There are mainly two types of QSFP28 direct attach cables: QSFP28 to QSFP28 DAC and QSFP28 to SFP28 DAC. The former is length of copper cable terminated with a QSFP28 connector on each end. The latter is a length of breakout cable with one end terminated with QSFP28 connector and the other terminated with four SFP28 modules. QSFP28 to SFP28 DAC can achieve the 25G to 100G transmission. The length of QSFP28 DAC is usually up to 5 meters which can cover a wide range of applications in data center.
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