CFP (C Form-Factor Pluggable) and CFP4 (C Form-Factor Pluggable 4) are two generations of optical transceiver form factors, designed to provide high-speed connectivity in networking applications. Here are the key differences between CFP and CFP4: 

1. Size and Form Factor:

• CFP:

• CFP is the original form factor and stands for C Form-Factor Pluggable.

• It has a larger physical size compared to CFP4.

• CFP4:

• CFP4 is a more compact and smaller version of the CFP form factor.

• The "4" in CFP4 indicates that it is the fourth generation of the CFP family.

2. Data Rates:

• CFP:

• CFP modules support a wide range of data rates, including 40 Gbps and 100 Gbps.

• CFP4:

• CFP4 modules are designed to support similar data rates but in a more compact form factor.

3. Port Density:

• CFP:

• CFP modules are larger, and their size can limit port density on networking equipment.

• CFP4:

• CFP4's smaller form factor allows for higher port density, making it suitable for applications where space is a premium.

4. Use Cases:

• CFP:

• CFP modules are used in a variety of networking applications, including 40GbE and 100GbE connections.

• CFP4:

• CFP4 modules are also used for 40GbE and 100GbE connections but are designed to provide a more compact and space-efficient solution.

5. Compatibility:

• CFP:

• CFP modules and CFP4 modules are not physically interchangeable due to the differences in form factor.

• CFP4:

• CFP4 modules are not backward compatible with CFP slots. They are designed for CFP4-compatible ports.

6. Evolution:

• CFP:

• CFP was the initial form factor introduced to support high-speed data rates.

• CFP4:

• CFP4 represents a newer generation with a focus on miniaturization and increased port density while maintaining support for high data rates.

In summary, the primary difference between CFP and CFP4 is the form factor, with CFP4 being a smaller and more space-efficient version. Both are designed to support high-speed data rates, and the choice between them depends on factors such as physical space constraints, port density requirements, and specific networking application needs. CFP4 is a more recent development, and its adoption is influenced by the evolving demands of modern network infrastructure.