What is UPC?
Ultra Physical Contact (UPC) describes how the end of a fiber connector's ferrule is polished. The end face is polished at 0 degrees with a slight dome, so the fiber cores of two mated connectors touch with no air gap. UPC is a finer, extended version of the older PC (physical contact) polish, which lowers back reflection.
UPC vs. APC
| UPC | APC | |
|---|---|---|
| End face | Domed, 0 degrees | Angled 8 degrees |
| Usual color | Blue | Green |
| Return loss (back reflection) | About -50 dB | About -60 dB or better |
| Common use | Ethernet and other data links | FTTH/PON, cable TV video and other reflection-sensitive links |
Never mate a UPC connector with an APC connector. The end faces don't meet properly, which causes high loss and can damage both. The polish type is often part of the connector's name, such as SC/UPC or LC/APC.
For the CompTIA A+ exam
Core 1 covers the fiber connector types SC, ST and LC. UPC and APC aren't connector types; they're polish styles any of those connectors can have. On a fiber patch panel, blue usually means UPC and green means APC.