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Is QSFP+ compatible with SFP28?
Knowledge Base + 2024.01.09

No, QSFP+ (Quad Small Form-Factor Pluggable Plus) and SFP28 (Small Form-Factor Pluggable Plus for 25 Gbps) are not directly compatible due to differences in form factor and electrical specifications. QSFP+ and SFP28 have distinct physical designs and are intended for different data rates, despite both being part of the same SFP+ family.

Here are the key differences:

  1. Form Factor:

    • QSFP+: QSFP+ has a larger form factor than SFP28. It supports four channels for high-speed data transmission.

    • SFP28: SFP28 is a smaller form factor designed for 25 Gigabit Ethernet applications. It has a single channel for transmitting data at 25 Gbps.

  2. Electrical Specifications:

    • QSFP+: QSFP+ operates at various data rates, including 40 Gbps or 4 x 10 Gbps (quad-channel). It has a higher aggregate data rate compared to SFP28.

    • SFP28: SFP28 operates at a fixed data rate of 25 Gbps on a single channel.

  3. Compatibility:

    • QSFP+ ports are typically designed to support QSFP+ modules and are not electrically compatible with SFP28 modules.

    • SFP28 ports are designed specifically for SFP28 modules, and inserting a QSFP+ module into an SFP28 port is not supported.

While QSFP+ and SFP28 are not directly interchangeable, it's important to note that there are devices called "breakout cables" or "splitter cables" that can enable connectivity between them. For example, a QSFP+ to 4x SFP28 breakout cable allows you to connect a QSFP+ port to four separate SFP28 ports, effectively utilizing the channels individually. However, this requires the appropriate breakout cable and support from the networking equipment.

Always check the specifications and compatibility requirements of the specific networking equipment and transceivers you are using to ensure proper functionality.