The speed of a QSFP (Quad Small Form-Factor Pluggable) transceiver can vary depending on the specific variant and generation. QSFP modules are designed to support high-speed data transmission in data center and high-performance computing environments. Here are some common QSFP variants and their associated speeds: 

1. QSFP:

• Data Rate: QSFP modules were initially introduced to support data rates up to 40 Gigabits per second (Gbps).

• Applications: Commonly used for 40 Gigabit Ethernet (40GbE) connections.

2. QSFP+:

• Data Rate: QSFP+ modules support data rates up to 40 Gbps (4 x 10 Gbps) and are backward compatible with the original QSFP modules.

• Applications: Used for 40GbE and 10 Gigabit Ethernet (10GbE) connections.

3. QSFP28:

• Data Rate: QSFP28 modules support data rates up to 100 Gbps (4 x 25 Gbps).

• Applications: Widely used for 100GbE connections and other high-speed networking applications.

4. QSFP56:

• Data Rate: QSFP56 modules support data rates of 200 Gbps and 400 Gbps, making them suitable for higher-bandwidth requirements.

• Applications: Used for 200GbE and 400GbE connections.

5. QSFP-DD (Double Density):

• Data Rate: QSFP-DD modules support even higher data rates, including 200 Gbps and 400 Gbps per module.

• Applications: Designed for next-generation high-density and high-speed networking applications.

It's important to note that the term "QSFP" by itself may refer to the original QSFP or QSFP+ modules, and the specific data rate will depend on the generation of the module. Advancements in technology have led to higher-speed variants like QSFP28, QSFP56, and QSFP-DD to meet the increasing demand for faster data transmission in modern data centers and networks.

Always refer to the documentation provided by the equipment manufacturer for accurate information on the supported data rates of QSFP modules in your network infrastructure.