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Things You May Want to Know About 100G QSFP28 【FAQs】

December 22, 2021

100G QSFP28 is designed to carry 100 Gigabit Ethernet, providing a high-density and high-speed solution for data centers and high-performance computing networks. What does QSFP28 refer to? How many types of QSFP28 transceivers are there in the market? Find answers in this article.

FAQs on 100G QSFP28 Definition and Types

Q1: What does QSFP28 stand for?

A: QSFP28 is abbreviated from Quad Small Form-Factor Pluggable 28. The 100G QSFP28, implemented with four channels of high-speed differential signals with data rates ranging from 25Gbps up to potentially 40Gbps, is designed for 100 Gigabit Ethernet, EDR InfiniBand, and 32G Fibre Channel.

Q2: What are the types and specifications of QSFP28 transceivers?

A: The types and main specifications of 100G QSFP28 are shown in the following diagram.

QSFP28 Industry Standards Max Cable Distance Optical Connector Fiber Type to Be Used
100GBASE-SR4 IEEE 802.3bm, QSFP28 MSA, SFF-8665, SFF-8636, RoHS, CPRI, eCPRI 100m MTP/MPO-12 MMF
100GBASE-LR4 IEEE 802.3ba 100GBASE-LR4, IEEE 802.3bm, QSFP28 MSA, SFF-8665, SFF-8636 10km LC Duplex SMF
100GBASE-ER4 QSFP28 MSA Compliant 40km LC Duplex SMF
100GBASE-ZR4 QSFP28 MSA Compliant 80km LC Duplex SMF
100GBASE-DR IEEE 802.3cd 100GBASE-DR Specification compliant 500m LC Duplex SMF
100GBASE-FR 100G Lambda MSA 100G-FR Specification compliant 2km LC Duplex SMF
100GBASE-LR 100G Lambda MSA 100G-LR Specification compliant 10km LC Duplex SMF
100GBASE-PSM4 QSFP28 MSA Compliant 500m MTP/MPO-12 SMF
100GBASE-CWDM4 IEEE 802.3ba, IEEE 802.3bm, SFF-8665, SFF-8636, 100G CWDM4 MSA, QSFP28 MSA 2km LC Duplex SMF
100GBASE-4WDM QSFP28 MSA Compliant 10km LC Duplex SMF
100GBASE-DWDM IEEE 802.3bm, QSFP28 MSA, SFF-8636, SFF-8024 80km CS Duplex SMF
100GBASE-BiDi QSFP28 MSA Compliant 20km LC Simplex SMF

Q3: What is 100G BiDi transceiver?

A: The 100G BiDi transceiver refers to the QSFP28 single-mode fiber bidirectional optical module applied to 100G Ethernet. Each optical port on the QSFP28 BiDi contains both a transmitter and receiver, transmitting and receiving data to/from interconnected network devices (like network switches or routers) at full-duplex 50Gbps via a single optical fiber. QSFP28 BiDi modules are high-quality solutions for data communication and interconnect applications with the lowest cost in infrastructure.

FAQs on 100G QSFP28 Applications

Q1: What is the operating temperature range of 100G QSFP28 transceivers?

A: The standard operating temperature range of QSFP28 module commercial version is 0°C to 70°C and that of industrial version is -40 to 85°C. Commercial version transceivers are generally applied. There are also some data centers that use 100G transceivers with operating temperatures ranging from 20°C to 50°C to reduce costs.

Q2: Are there any dual-rate 100G optical transceivers to avoid costly replacement when I upgrade?

A: Yes, there are 100G/112G and 40G/100G dual-rate modules. FS QSFP-100/112G dual-rate transceiver is designed for use in 100GBASE Ethernet and 4x28G OTN client interfaces with low power consumption, ideal for telecom and 5G wireless network applications.

Q3: QSFP28 vs QSFP+ vs 100G CFP vs QSFP-DD: What are the differences?

A: The main differences between the four types of transceivers are shown below:

Form Factor QSFP28 QSFP+ 100G CFP QSFP-DD
Number of Electrical Interface Lanes 4 4 4 4
Single Channel Rate 25Gbps 10Gbps 25Gbps 25Gbps/50Gbps
Modulation Technology NRZ NRZ NRZ NRZ/PAM4
Applications 100G Ethernet 40G Ethernet 40G/100G Ethernet 400G Ethernet

For more information: 100G CFP vs QSFP28: When to Use Each?

Q4: What are the applications of QSFP28 transceivers?

A: Based on different transmission distances, 100G QSFP28 can be applied in various scenarios such as interconnections between racks, switches, long-distance telecommunications, etc. To learn more: How to Choose the Right 100G QSFP28 Optical Transceivers?

FAQs on Using 100G QSFP28 in Data Centers

Q1: Can I use QSFP+ optics on QSFP28 ports?

A: Yes, 100G QSFP28 ports can generally take either QSFP+ or QSFP28 optics. QSFP28 transceivers have the same form factor as the QSFP+ optical modules, and a QSFP28 module can break out into either 4x 25G or 4x 10G lanes, which depends on the transceiver used. It means that QSFP+ optics can be used on the QSFP28 ports at a lower 40G speed. But QSFP28 modules can not be used on QSFP+ ports as the speed of the ports is lower than that of the optics used.

Q2: Can 100G QSFP28 interfaces interoperate with SR10 based 100GbE?

A: No. The QSFP28 form factor has just 4 electrical lanes, which is not enough to support 10 lanes of 10G electrical interface. A QSFP 100G can only support a 4x 10G or 4x 25G electrical interface, which can be used as 4x 10GbE or 4x 25GbE, but not 10x 10GbE. As a result, the 100G QSFP28 interfaces cannot interoperate with SR10 based 100GbE transceivers.

Q3: Can QSFP28 transceiver work with CFP transceiver?

A: Yes, both are products of the Ethernet protocol and can interoperate with each other.

Q4: How to breakout 100G to 4x 25G?

A: A simple 100G to 4x 25G breakout connection can be made between one QSFP28 SR4 transceiver and four SFP28 transceivers with breakout cables. In addition to 100G transceivers, breakouts can also be implemented with AOCs or DACs.

Q5: Does the 100G QSFP28 need to use the FEC function?

A: Not all QSFP28 transceivers need FEC function, as the process of correcting error code will inevitably cause some data packet delay. FEC (Forward Error Correction) is a method to increase the credibility of data communication by correcting errors during signal transmission. When an error occurs in the transmission, the receiver is allowed to reconstruct the data. In the design of transceivers, the cost of FEC function is relatively high and is generally rarely used.

Related Article:

Differences Between QSFP-DD and QSFP+/QSFP28/QSFP56/OSFP/CFP8/COBO

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