CFP (C Form-Factor Pluggable) and QSFP28 (Quad Small Form-Factor Pluggable 28) are both types of optical transceiver form factors, but they differ in terms of their physical size, data rates, and applications. Here are the key differences between CFP and QSFP28:

1. Form Factor:

• CFP: CFP has a larger form factor compared to QSFP28. It was designed to support a wide range of data rates and applications, including 40G and 100G.

• QSFP28: QSFP28 has a more compact form factor. It is specifically designed for 100 Gigabit Ethernet (100GbE) applications and provides a smaller footprint, allowing for higher port density on networking equipment.

2. Data Rates:

• CFP: CFP modules support various data rates, including 40 Gbps and 100 Gbps. There are different CFP module types, such as CFP, CFP2, and CFP4, each supporting different data rates and form factors.

• QSFP28: QSFP28 is primarily designed for 100 Gbps data rates, with four electrical lanes operating at 25 Gbps each.

3. Applications:

• CFP: CFP is used in a broader range of applications, including both 40G and 100G connections. It is employed in various networking scenarios, such as data center interconnects and telecommunications networks.

• QSFP28: QSFP28 is specifically targeted at 100GbE applications and is commonly used in data center environments for high-speed connectivity.

4. Port Density:

• CFP: Due to its larger size, CFP modules may result in lower port density on networking equipment compared to smaller form factors.

• QSFP28: The smaller form factor of QSFP28 allows for higher port density, making it suitable for environments where maximizing the number of connections in a limited space is important.

5. Modularity:

• CFP: CFP is available in different types (CFP, CFP2, CFP4) to accommodate varying data rates and form factor preferences.

• QSFP28: QSFP28 is a unified form factor specifically designed for 100GbE applications, offering a standardized and compact design.

When choosing between CFP and QSFP28, considerations include the targeted data rates, the specific requirements of the networking environment, and the form factor preferences of the equipment being used. Advances in technology have led to the development of smaller and more efficient form factors, such as QSFP28, for higher-speed applications like 100GbE.