What does 28 on the optical module represent

The "28" in SFP28 indicates that the module supports a data rate of 25 Gbps per lane.SFP28 (Small Form-factor Pluggable 28) is a high-speed optical transceiver designed for 25G Ethernet and 32G Fibre Channel applications . The "28" does not refer to the physical size but rather to the enhanced electrical interface capable of handling 25 Gbps, which is higher than the 10 Gbps supported by SFP+ modules . SFP28 modules are physically identical to SFP and SFP+ modules, allowing backward compatibility while providing higher bandwidth for modern networks .Key Features of SFP28Speed: Supports 25 Gbps per lane, enabling 100G aggregation when used in four-lane configurations (4x25G) for QSFP28 modules .Use Cases: Ideal for data center access layers, 100G aggregation, and high-speed SANs. It provides a cost-effective upgrade path from 10G networks .Compatibility: SFP28 modules are backward compatible with 10G and 25G Ethernet, making them versatile for mixed-speed environments .Form Factor: Same compact size as SFP and SFP+, allowing high port density in switches and routers .ApplicationsSFP28 modules are widely used in modern enterprise networks, data centers, and carrier-grade deployments. They support both Ethernet and Fibre Channel protocols, providing reliable, high-speed connectivity while maintaining compatibility with existing infrastructure . They are also a key building block for 100G networks, where four SFP28 lanes can be combined in QSFP28 modules to achieve 100 Gbps throughput . In summary, the "28" in SFP28 signifies the module's capability to handle 25 Gbps per lane, offering higher bandwidth than previous SFP generations while maintaining the same physical form factor for easy deployment and backward compatibility .