ultra physical contact (fiber optics) (UPC)
For the end face coupling ofoptical fibers, the aim is to connect the optical fibers to each other with the lowest possible attenuation and few reflections. To achieve this, the end faces of the optical fibers in the FO connectors are given a specific shape and polished.
A simple surface shape is the convex one, which is ground and polished to achieve the lowest possible insertion loss( IL) and high return loss. Depending on how fine the grinding and polishing are, convex ground end faces are classified as Physical Contact( PC), Super Physical Contact( SPC) and Ultra Physical Contact(UPC).
The UPC end face is more rounded than the PC end face and is extremely finely polished. It has the best values as far as curved end faces are concerned: the return loss is above 50 dB and the insertion loss is below 0.3 dB.