Which Ethernet PHY to use for 100Base-FX (SFP) operation?

For new designs I primarily recommend the Texas Instruments DP83822. It comes in a 5x5mm QFN package and provides RMII, MII and even RGMII interfaces to the Microcontroller or other Ethernet MAC.

**Be sure to select the DP83822xF -**the F means Fiber!

Since at the time of writing this article, the DP83822has supply shortages, the following alternatives are available for 100Base-FX operation:

Compared to the DP83822, within the context of 100Base-FX operation, there are few technical differences in whether you use the DP83822. In my experience, Ethernet PHYs are mostly difference with regards to their electrical immunity (ESD and so on) which is not really relevant in the fiber context unless someone directly touches the PCB, and the ability to compensate for a degrated Ethernet signal (which is not really relevant for fiber contexts). **The only real difference between the DP83822 and many other parts is that the DP83822 comes in a small VQFN package, which the Micrel/Microchip KSZ devices come in much larger SSOP or LQFP packages.**My recommendation is to select based on availability first, on size second.