The bandwidth of a QSFP+ (Quad Small Form-Factor Pluggable Plus) transceiver is determined by the data rate it supports, which is typically expressed in gigabits per second (Gbps). QSFP+ modules are designed to provide high-speed data transmission in data center and networking applications. The bandwidth is directly related to the number of electrical lanes and the data rate per lane.

Here are some common QSFP+ variants and their associated bandwidths:

1. QSFP+ (4x10G):

• Data Rate per Lane: 10 gigabits per second (Gbps)

• Total Bandwidth: 4 lanes x 10 Gbps = 40 Gbps

2. QSFP+ (4x25G):

• Data Rate per Lane: 25 gigabits per second (Gbps)

• Total Bandwidth: 4 lanes x 25 Gbps = 100 Gbps

3. QSFP28 (4x25G):

• Data Rate per Lane: 25 gigabits per second (Gbps)

• Total Bandwidth: 4 lanes x 25 Gbps = 100 Gbps

4. QSFP56 (4x50G):

• Data Rate per Lane: 50 gigabits per second (Gbps)

• Total Bandwidth: 4 lanes x 50 Gbps = 200 Gbps

5. QSFP-DD (8x25G):

• Data Rate per Lane: 25 gigabits per second (Gbps)

• Total Bandwidth: 8 lanes x 25 Gbps = 200 Gbps

The total bandwidth is the sum of the data rates across all the lanes in the QSFP+ module. The naming conventions often include the number of lanes and the data rate per lane (e.g., 4x10G or 4x25G), providing a clear indication of the module's capabilities.

When selecting QSFP+ modules, it's important to consider the specific data rates required for the intended application, as different configurations offer varying levels of bandwidth to meet the demands of different networking scenarios. Always refer to the module's datasheet or specifications for accurate information on supported data rates and bandwidth.