The term "QSFP28" stands for "Quad Small Form-Factor Pluggable 28," and it refers to a specific form factor for optical transceivers. The "28" indicates that it supports a data rate of 28 gigabits per second (Gbps) per channel. Therefore, a QSFP28 module can support various data rates depending on the specific application and the number of channels utilized. The two common data rates associated with QSFP28 modules are 40 Gbps and 100 Gbps:

1. 40 Gigabit Ethernet (40GbE):

• In a 40GbE configuration, a QSFP28 module may use a single channel to transmit data at 40 Gbps.

2. 100 Gigabit Ethernet (100GbE):

• In a 100GbE configuration, a QSFP28 module may use multiple channels (typically four channels) to achieve an aggregate data rate of 100 Gbps.

So, the QSFP28 form factor is versatile and can be used for both 40 Gbps and 100 Gbps applications. The specific data rate depends on how the module is configured and the standards it adheres to in a given networking environment. QSFP28 is commonly used in high-speed data center and telecommunications networks to support these higher data rates.