A QSFP28 (Quad Small Form-Factor Pluggable 28) transceiver supports a total of four electrical lanes. Each lane can carry data at a rate of up to 25 gigabits per second (Gbps). The aggregate data rate of a QSFP28 module is thus 100 Gbps, combining the four lanes.

The design of QSFP28 allows it to support high-speed data transmission, making it a common choice for applications such as 100 Gigabit Ethernet (100GbE) in data centers and high-performance computing environments. Keep in mind that the term "28" in QSFP28 refers to the fact that each lane operates at 28 Gbps, but the standard is often used for 25 Gbps applications, resulting in a total aggregate data rate of 100 Gbps.

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

A: The standard operating temperature range of QSFP28 100G module commercial version is 0°C to 70°C and that of the 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. QSFP-100/112G dual-rate transceiver is designed for use in 100GBASE Ethernet and 4x 28G 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:

Q4: What are the applications of QSFP28 100G 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. 

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. However, 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 the CFP transceiver?

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

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

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.