The QSFP28 (Quad Small Form-Factor Pluggable 28) module has a mechanical form factor with specific dimensions. The dimensions are standardized by industry specifications to ensure compatibility and interoperability between different vendors' products. The main mechanical dimensions of a QSFP28 module are as follows: 

100G QSFP28 LR1/ER1

1. Overall Dimensions:

• Width: 18.35 mm (0.722 inches)

• Height: 8.5 mm (0.335 inches)

• Depth: 71.5 mm (2.818 inches)

2. Connector Interface:

• The connector interface is an MPO (Multi-Fiber Push-On) or MTP (Multi-fiber Termination Push-On) connector with 12 fibers for transmitting and 12 fibers for receiving (total 24 fibers).

3. Port Configuration:

• The module has a 1x4 electrical interface (one row of 4 lanes) for transmitting and another 1x4 electrical interface for receiving.

4. Cable Type:

• QSFP28 modules typically use multimode or single-mode fiber optic cables, depending on the application and distance requirements.

These dimensions and specifications ensure that QSFP28 modules can be used in compatible ports and cages in networking equipment such as switches and routers. It's important to note that while the mechanical form factor is standardized, the electrical and optical characteristics (such as data rate and transmission distance) can vary depending on the specific type and standard of the QSFP28 module (e.g., 100GBASE-SR4, 100GBASE-LR4).