Fiber-optic connectors use spring-loaded metal or ceramic ferrules. The optical fibers are cemented into the ferrules.

This allows the fiber to be polished together with the end of the ferrule to optimize the contact of the fiber with the SFP's optical surface.

This allows a very low insertion loss for the connection of about 0.1 - 0.5dB.

There are different options to realize this polish. Most often you'll see the abbreviations PC, SPC, UPC, and APC.

These stand for:

Physical Contact (PC)

Super Physical Contact (SPC)

Ultra Physical Contact (UPC)

Angled Physical Contact (APC)

LYNX fiber-optic components support optical connectors with polish options PC, SPC, and UPC.