This Will Change Your Perspective About The Difference Between SFP,SFP+,SFP28, QSFP+ And QSFP28

SFP, SFP+, SFP28, QSFP+, and QSFP28 are hot-swappable modules used to connect network switches and other network devices (such as servers or transceivers) for data transmission. But do you understand the specific differences between these modules? Are QSFP28 and QSFP+ compatible? Can SFP28 modules be used in SFP+ slots? If you have these questions, read on as this article will provide the answers.

Understanding the Types of Optical Modules

Before clarifying the differences between these modules, it's essential to understand what SFP, SFP+, SFP28, QSFP, and QSFP28 are. Below is a description of each module.

SFP:

SFP can be seen as an upgraded version of GBIC, with a size that is only half that of the GBIC module, significantly increasing the port density of network devices. The data transmission rate of SFP ranges from 100 Mbps to 4 Gbps.

SFP+:

SFP+ is an enhanced version of SFP, supporting 8 Gbit/s Fibre Channel, 10 G Ethernet, and the optical transport network standard OTU2. Additionally, SFP+ direct attach cables (i.e., SFP+ DAC high-speed cables and AOC active optical cables) can connect two SFP+ ports without adding extra optical modules or cables, making it a good choice for directly connecting two nearby switches over short distances.

SFP28:

SFP28 is an improved version of SFP+ and has the same dimensions, but it supports a single-channel rate of 25 Gbps. SFP28 provides an efficient solution for upgrading from 10G to 25G to 100G networks, meeting the growing demands of next-generation data center networks.

QSFP+:

QSFP+ is the upgraded version of QSFP. While QSFP can support 4-channel transmission with each channel having a data rate of 1 Gbit/s, QSFP+ differs by supporting 4×10 Gbit/s channel transmission, allowing for a total transmission rate of 40 Gbps. Compared to SFP+, the QSFP+ optical module offers up to four times the transmission rate, making it effective for deploying 40G networks and increasing port density while saving costs.

QSFP28:

QSFP28 was developed to meet the demands of 100G applications, featuring four high-speed differential signal channels, each capable of transmission rates ranging from 25 Gbps to potentially 40 Gbps, fulfilling the needs of 100G Ethernet (4×25 Gbps) and EDR InfiniBand applications. QSFP28 comes in various types to achieve 100G transmission, including 100G direct attach, 100G to 4×25G branch links, or 100G to 2×50G branch links.

Differences and Similarities Among SFP, SFP+, SFP28, QSFP+, and QSFP28

After understanding what SFP, SFP+, SFP28, QSFP+, and QSFP28 are, let's look at the specific differences and similarities between them.

SFP vs. SFP+: Same Size, Different Rates and Compatibility

SFP and SFP+ modules look identical in size, allowing manufacturers to use the same physical design for devices with SFP+ ports. Because of their identical dimensions, many customers use SFP modules in SFP+ ports; this is feasible, but the rate will drop to 1 Gbit/s. It’s important to note that SFP+ modules cannot be used in SFP slots, as this may damage the port or module. Besides the compatibility issue, SFP and SFP+ differ in transmission rates and standards. SFP can transmit up to 4 Gbit/s, while SFP+ can transmit up to 10 Gbit/s; SFP is based on the SFF-8472 protocol, while SFP+ is based on the SFF-8431 and SFF-8432 protocols.

SFP28 vs. SFP+: SFP28 Modules Can Be Used in SFP+ Ports

As previously mentioned, SFP28 is an upgraded version of SFP+, and both have the same dimensions but different transmission rates: SFP+ has a rate of 10 Gbit/s, while SFP28 has a rate of 25 Gbit/s. If an SFP+ module is inserted into an SFP28 port, the link transmission rate will be 10 Gbit/s, and vice versa. Additionally, SFP28 direct attach copper cables have higher bandwidth and lower loss compared to SFP+ direct attach copper cables.

SFP28 vs. QSFP28: Different Protocol Standards

Although both SFP28 and QSFP28 have the digit "28," their sizes and protocol standards are different. SFP28 supports 25 Gbit/s single-channel transmission, while QSFP28 supports four 25 Gbit/s channels. Both can be used in 100G networks, but in different ways; QSFP28 can achieve 100G transmission through several methods mentioned earlier, while SFP28 requires a QSFP28 to SFP28 branch high-speed cable.

QSFP vs. QSFP28: Different Rates, Different Applications

QSFP+ and QSFP28 optical modules have the same size, both featuring four integrated transmit and receive channels. However, the rates differ: QSFP+ supports a single-channel rate of 40 Gbit/s, while QSFP+ DAC/AOC supports 4×10 Gbit/s transmission. QSFP28 transmits data at 100 Gbit/s, with QSFP28 DAC/AOC supporting either 4×25 Gbit/s or 2×50 Gbit/s. Note that QSFP28 modules cannot be used for 10G branch links, but if a switch with a QSFP28 port supports QSFP+ modules, a QSFP+ module can be inserted into the QSFP28 port to achieve a 4×10 Gbit/s branch link.

Conclusion

This article has provided a detailed explanation of the differences between SFP and SFP+, SFP28 and SFP+, and QSFP+ and QSFP28 optical modules. Although some of them are similar in size, their operating rates are different. The comparison clearly shows that the main driving force behind the development of optical modules is to achieve higher bandwidth while maintaining smaller sizes, as evidenced by the fact that QSFP28 and QSFP+ share the same size but offer higher bandwidth.