The everyday word fiber crews use for the fiber strands and, by extension, for the whole installed plant. You hear it in phrases like bare glass, dark glass, pulling glass and how much glass is in that route. It separates fiber people from copper people, who talk about pairs and wire.
Don't set anything on that tray, there's bare glass all over the bench from the last closure.
Bare glass slivers are the real hazard on a splice bench: they work into skin and eyes, so crews use a fiber trash can and never brush scraps off with a hand.
Related terms
Core
The central glass region of an optical fiber where the light actually travels.
Cladding
The layer of slightly lower-index glass around the core that keeps light trapped inside it.
Dark fiber
Installed fiber with no transmission equipment attached, either spare or leased bare to a customer who lights it.
Burn
Splicer slang for making fusion splices, from the electric arc that welds the glass.