The bandwidth of a QSFP28 (Quad Small Form-factor Pluggable 28) module depends on the specific type and standard. QSFP28 modules are commonly used for high-speed data communication in networking equipment. The "28" in QSFP28 refers to the 28 gigabits per second (Gbps) data rate per channel. 

The most prevalent data rates for QSFP28 modules include:

1. 100G QSFP28:

• QSFP28 modules are widely used for 100 Gigabit Ethernet (100GbE) applications. This involves four channels, each operating at 25 Gbps, to achieve the total 100 Gbps data rate.

2. 40G QSFP28:

• In some cases, QSFP28 modules might be used in a 40 Gigabit Ethernet (40GbE) configuration, where only one channel is utilized for 40 Gbps data transmission.

3. Other Data Rates:

• QSFP28 modules may also support higher data rates, such as 200G or 400G, depending on the specific standard (like QSFP28-DD for double density) and the use of advanced modulation techniques.

In summary, while the baseline QSFP28 modules are commonly associated with 100G data rates, there are variations and advanced standards that can support higher data rates, providing flexibility for different networking requirements. Always check the specifications of the specific QSFP28 module you are using to determine its supported data rate and capabilities.