The main difference between QSFP (Quad Small Form-factor Pluggable) 100G and QSFP28 lies in their data transfer rates and the associated standards. Both are types of QSFP modules used for high-speed data transmission in networking applications. Here's a breakdown of the differences:

1. Data Transfer Rate:

• QSFP 100G: QSFP 100G typically refers to a QSFP module that supports a data transfer rate of 100 gigabits per second (Gbps). It is associated with standards like 100 Gigabit Ethernet.

• QSFP28: QSFP28 is an enhanced version of QSFP designed to support higher data rates. QSFP28 modules commonly support data rates of 100 Gbps but can also be used for higher data rates such as 40 Gigabit Ethernet or even 25 Gigabit Ethernet.

2. Form Factor:

• Both QSFP 100G and QSFP28 modules have a similar form factor, but the QSFP28 module has additional electrical contacts to support the higher data rates.

3. Applications:

• QSFP 100G: Primarily used for 100 Gigabit Ethernet connections.

• QSFP28: Used for a range of applications, including 100 Gigabit Ethernet, 40 Gigabit Ethernet, and potentially 25 Gigabit Ethernet, depending on the specific implementation.

4. Compatibility:

• QSFP 100G: Generally compatible with devices and switches designed for 100 Gigabit Ethernet.

• QSFP28: Backward compatible with QSFP modules and ports but designed to support higher data rates, offering increased flexibility for network upgrades.

In summary, while both QSFP 100G and QSFP28 modules can support 100 Gbps data rates, QSFP28 is an enhanced version that provides additional flexibility by supporting other data rates and being backward compatible with QSFP modules and ports.