APC: Abbreviation for Angled Physical Contact. A type of connector with an angled endface designed to minimize backreflection.
Armor: A protective coating around (or integrated into) a fiber optic cable
Attenuation: The decrease in signal strength between two points in a fiber optic waveguide, usually expressed in dB.
Attenuator (as relates to optical networks): A passive device designed to reduce signal strength while minimally distorting the waveform.