It seems there might be a typo or a misunderstanding in your question. As of my last knowledge update in January 2022, there isn't a widely recognized term or standard for "spf28" in the context of optical transceivers or networking components. It's possible that there may be a typo, or it could be a term specific to a certain vendor or application.

However, if you meant "SFP28" rather than "spf28," I can provide a comparison between QSFP28 and SFP28:

1. QSFP28 (Quad Small Form-Factor Pluggable 28):

• Form Factor: Larger form factor compared to SFP28.

• Data Rate: Supports higher data rates, typically up to 100 gigabits per second (Gbps) or more.

• Applications: Commonly used for high-speed connections in data centers and high-performance computing environments. Suitable for applications such as 100 Gigabit Ethernet.

2. SFP28 (Small Form-Factor Pluggable 28):

• Form Factor: Smaller form factor compared to QSFP28.

• Data Rate: Supports data rates up to 25 gigabits per second (Gbps).

• Applications: Used for high-speed connections where the form factor of QSFP28 is not practical. Suitable for applications such as 25 Gigabit Ethernet.

Both QSFP28 and SFP28 are types of optical transceiver modules designed for high-speed data transmission in networking equipment. The choice between them depends on factors such as the required data rate, form factor considerations, and compatibility with the networking infrastructure.

If "spf28" refers to a different term or has become a recognized standard after my last update, I recommend checking the latest industry documentation or vendor specifications for accurate information.