Understanding the Differences Between SFP and QSFP Module

In low-speed networks, SFP and QSFP are the most widely used packages, basically covering all low-speed network scenarios. With their small size, low power consumption, low cost, and high adaptability, they have become the preferred choice for low-speed networks. This article will take a detailed look at the differences between these two packages, making them the preferred choice for all network engineers.

1. What are SFP and QSFP?

For many, SFP and QSFP should be familiar; they are the packages for optical modules, representing the common standards for optical module production and design.

SFP (Small Form-factor Pluggable) packaging was introduced to address the issues of large size and high power consumption in optical modules. It was one of the first optical module packages to be introduced, featuring a compact design with dimensions of approximately 56.5mm × 13.4mm × 8.5mm and a weight of only 10-15g. It supports hot-swapping. Initially designed as a single-channel structure, it was later adapted to meet the demands of higher speeds by adopting a dual-channel standard, SFP-DD, without changing the overall size. This standard supports speeds up to 100G, satisfying the requirements of high-speed and small-size transmission.

QSFP (Quad Small Form-factor Pluggable) is an upgraded version of SFP, increasing the module's bandwidth by adding more channels. Consequently, QSFP requires more space to accommodate the increased number of channels, making it larger than SFP (approximately 78mm × 18.3mm × 8.5mm) and weighing 20-30g. It also supports hot-swapping. The QSFP design uses a four-channel parallel structure, with all four channels transmitting data together to meet high-speed transmission requirements.

2. Speed

Differences between SFP and QSFP

SFP uses a single-channel structure. Limited by the number of channels, the overall speed cannot be increased. With traditional NRZ modulation, the maximum speed is 25G; with PAM4 modulation, it's up to 50G; and with the latest SFP-DD dual-channel technology, the speed can be increased to 100G.

QSFP uses a four-channel structure. In its early development, 40G was sufficient, but with the development of network speeds, 40G became inadequate. Increasing the number of channels within the QSFP package couldn't overcome size limitations. Therefore, engineers focused on modulation methods, employing PAM4 modulation to successfully increase the speed to 100G for QSFP28 and 200G for QSFP56. Finally, they doubled the number of channels, resulting in the even higher-speed QSFP-DD, capable of supporting 800G and even ultra-high speeds of 1.6T.

3. SFP and QSFP Application Scenarios

SFP and QSFP differ significantly in various aspects, leading to substantial differences in their application scenarios. SFP is small, has a lower speed, and is relatively cheaper than QSFP, making it suitable for high-density cabling in low-speed networks. It is widely used in home networks, enterprise office networks, and industrial production networks, providing stable and efficient network connectivity for these low-speed networks.

QSFP offers high speed, large bandwidth, moderate power consumption, and low cost, making it suitable for network environments with high speed requirements, such as enterprise network core rooms, metropolitan area networks, and traditional data center networks. In these environments, the network infrastructure is more robust and can support higher power consumption and larger size QSFP optical modules.

4. Conclusion

This article has explored the differences between SFP and QSFP through a detailed comparison of their packaging forms, speeds, and application scenarios. They are not upgrades or replacements, but rather focus on different network environments, each with its own specific role in different networks, jointly undertaking the most basic data transmission work and playing its part in building a stable network. YXFiber has been deeply involved in the communications industry for 10 years, committed to providing high-performance, reliable, and cost-effective SFP and QSFP optical modules to meet various network designs and add an extra layer of security to networks.