Angled Physical Contact, a polish in which the ferrule end face is ground at 8 degrees, so any light reflected at the joint is directed out of the core instead of back toward the source. Reflectance is typically better than minus 60 dB. APC connectors are color-coded green and are standard on PON, RF video overlay and other reflection-sensitive singlemode systems.
Everything past the OLT is green, APC only, if I see a blue connector in that cabinet it's coming out.
Green into green, blue into blue: mating APC to UPC can show 3 dB or more of loss and can chip both end faces.
Also heard as
- angled polish
- green connector
Do not mix it up with
- UPC: UPC is a domed polish with no angle and higher reflectance; plugging UPC into APC leaves an air gap and several dB of loss.
Related terms
UPC
Ultra Physical Contact: a domed singlemode connector polish with no angle, color-coded blue.
Reflectance
The fraction of light reflected by a single event such as a connector, in dB, where more negative is better.
Return loss
How much weaker reflected light is than the light sent in, in dB, where bigger numbers mean less reflection.
End face
The polished tip of a connector ferrule and fiber, where light leaves one fiber and enters the next.
PON
Passive Optical Network: a point-to-multipoint fiber network where unpowered splitters share one fiber among many users.