QSFP28 (Quad Small Form-factor Pluggable 28) and QSFP (Quad Small Form-factor Pluggable) are both types of transceiver modules used in high-speed network connections. The main difference between QSFP28 and QSFP lies in their data transmission capabilities.

The main difference between QSFP28 and QSFP lies in their maximum data rates.

1. QSFP (Quad Small Form-Factor Pluggable):

• Supports data rates of up to 10 Gbps per channel.

• It may be used for 40 Gbps aggregate data rates (4 channels).

• Initially developed for 40 Gigabit Ethernet (40GbE) applications.

2. QSFP28 (Quad Small Form-Factor Pluggable 28):

• Supports data rates of up to 28 Gbps per channel.

• It may be used for 100 Gbps aggregate data rates (4 channels).

• Developed to meet the higher data rate requirements of modern networking technologies, including 100 Gigabit Ethernet (100GbE).

In summary, QSFP28 is an enhanced version of the QSFP standard, providing higher data rates to meet the increasing demand for faster and more efficient data transmission in data centers and high-performance computing environments. QSFP28 modules are backward compatible with QSFP ports, but they offer the advantage of supporting higher speeds when used in QSFP28-enabled equipment.