In a QSFP28 (Quad Small Form-Factor Pluggable 28) module for 100 Gigabit Ethernet (100GbE) applications, there are typically four optical lanes, each operating at 25 gigabits per second (Gbps). These four lanes can be used for transmitting and receiving data independently, providing a total aggregate data rate of 100 Gbps.

The internal configuration of the QSFP28 module involves four separate electrical lanes, often referred to as 4x25G. Each lane corresponds to an independent optical transmitter and receiver pair. This parallel configuration enables high-speed data transmission and reception, making it suitable for 100GbE connections.

It's important to note that the use of multiple lanes allows for increased bandwidth and is a common approach in high-speed optical communication. In the case of QSFP28 for 100GbE, the four-lane configuration is the standard, providing an efficient and standardized solution for high-speed networking in data centers and other environments.

While the term "Quad" in QSFP originally indicated four channels, it's worth mentioning that newer form factors, such as QSFP-DD (Quad Small Form-Factor Pluggable Double Density), have been developed to support higher data rates, including 200G and 400G, by increasing the number of lanes. QSFP-DD modules, for example, can have eight or more lanes, each operating at 25 Gbps or higher.