The QSFP28 (Quad Small Form-Factor Pluggable 28) transceiver is designed for high-speed data transmission and typically supports data rates of 25 Gbps per lane. Since QSFP28 modules aggregate multiple lanes, they are primarily intended for applications with higher data rates, such as 100 Gigabit Ethernet (100GbE) or InfiniBand. 

While the QSFP28 module itself is not designed for 1 Gigabit Ethernet (1GbE) applications, there are cases where network devices with QSFP28 ports may be backward compatible with lower-speed transceivers using appropriate adapters or breakout cables. These breakout cables or adapters allow the QSFP28 port to be used with lower-speed transceivers, such as 1GbE SFP (Small Form-Factor Pluggable) modules.

It's important to note that while physical compatibility might be achieved, there are considerations related to signal integrity, power budgets, and other factors. Additionally, the use of such adapters may not be a standard practice, and compatibility should be confirmed with the specific hardware and software configurations.

If the primary requirement is for 1GbE connections, it is recommended to use dedicated SFP or SFP+ transceivers and ports designed for that data rate. QSFP28 ports are generally deployed in high-bandwidth scenarios, and using them for lower-speed applications may not be the most efficient or cost-effective solution. Always refer to the documentation provided by the hardware manufacturer for accurate information on supported data rates and compatibility.