Differences Between SFP, SFP+, SFP28, QSFP+,QSFP28

In the realm of high-speed data transmission, optical modules such as SFP, SFP+, SFP28, QSFP+, and QSFP28 play a pivotal role. These hot-swappable modules are widely used in network switches, servers, and other networking equipment. This article will delve into the characteristics of these optical modules and explore the differences among them.

I. Overview of Optical Module Types

Let's start with a basic understanding of SFP, SFP+, SFP28, QSFP+, and QSFP28 optical modules.

- SFP: An upgraded version of GBIC, smaller in size, supporting data transmission rates from 100Mbps to 4Gbps.

- SFP+: An enhanced version of SFP, supporting 8Gbit/s fiber channel, 10G Ethernet, and OTU2 standard.

- SFP28: An enhanced version of SFP+, supporting a single-channel rate of 25Gb/s, suitable for the upgrade of 10G-25G-100G networks.

- QSFP+: An upgraded version of QSFP, supporting 4-channel transmission at 1Gbit/s each, achieving a 40Gbps transmission rate.

- QSFP28: Designed for 100G applications, supporting 4 high-speed differential signal channels ranging from 25Gbps to a possible 40Gbps, meeting the requirements of 100G Ethernet (4×25Gbps) and EDR InfiniBand applications.

II. Compatibility and Differences Between Modules

Next, we will discuss the compatibility and specific differences between these modules.

- SFP and SFP+: The two have the same size, but SFP+ supports a higher transmission rate (10Gbit/s), while SFP supports up to 4Gbit/s. SFP modules can be used in SFP+ ports, but the rate will be reduced.

- SFP28 and SFP+: SFP28 modules are compatible with SFP+ ports, offering a higher 25Gbit/s transmission rate. SFP28 DAC cables have higher bandwidth and lower loss compared to SFP+ DAC.

- SFP28 and QSFP28: Although both support 25Gbps rates, SFP28 is a single channel, while QSFP28 provides four channels. QSFP28 can achieve 100G transmission through various methods mentioned above, but SFP28 relies on QSFP28-to-SFP28 branch high-speed cables.

- QSFP and QSFP28: Both have the same size, but QSFP+ supports a 40Gbit/s rate, and QSFP28 supports a 100Gbit/s rate. QSFP28 modules cannot be used for 10G branch channels, but if a switch with QSFP28 ports supports QSFP+ modules, QSFP+ modules can be inserted into QSFP28 ports to achieve 4×10G branch channels. Specific implementation methods can refer to the article "How to Utilize QSFP28 Ports for 10G/25G/40G Transmission."

III. Conclusion

This article has provided a detailed explanation of the differences between SFP, SFP+, SFP28, QSFP+, and QSFP28 optical modules. Although some may be similar in size, their operating rates and application scenarios vary. It is evident from the comparison that the main driving force behind the development of optical modules is the pursuit of higher bandwidth in smaller sizes, which is exemplified by the comparison between QSFP28 and QSFP+.

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