The range of a QSFP28 (Quad Small Form-Factor Pluggable 28) transceiver depends on the type of module and the optical fibers used. QSFP28 modules are available in different variants, and the range is influenced by factors such as the wavelength, fiber type (single-mode or multimode), and the specific application. Here are some common QSFP28 variants and their typical ranges:

1. SR4 (Short Range 4) QSFP28:

• Wavelength: Typically uses 850nm wavelength for multimode fiber.

• Range: Up to 100 meters over OM3 multimode fiber and up to 150 meters over OM4 multimode fiber.

2. LR4 (Long Range 4) QSFP28:

• Wavelength: Utilizes four separate wavelengths in the range of 1264.5nm to 1337.5nm for single-mode fiber.

• Range: Up to 10 kilometers.

3. ER4 (Extended Range 4) QSFP28:

• Wavelength: Similar to LR4, ER4 also uses four separate wavelengths in the range of 1264.5nm to 1337.5nm for single-mode fiber.

• Range: Extended range, typically up to 40 kilometers.

4. CWDM4 (Coarse Wavelength Division Multiplexing 4) QSFP28:

• Wavelengths: Utilizes four separate CWDM wavelengths in the range of 1271nm to 1331nm for single-mode fiber.

• Range: Up to 2 kilometers.

5. PSM4 (Parallel Single-Mode 4) QSFP28:

• Wavelength: Utilizes four separate wavelengths around 1310nm for single-mode fiber.

• Range: Typically up to 2 kilometers.

It's important to note that the range specified for each variant is a general guideline, and the actual performance may depend on factors such as the quality of the optical components, the specific implementation, and the condition of the fiber optic infrastructure. When selecting a QSFP28 module for a specific application, it's essential to consider the compatibility with the networking equipment and the optical characteristics required for the desired range. Always refer to the manufacturer's specifications for accurate information on the module's supported range.