Below we describe the main functions and features of each of PolyPhaser's five categories of passive fiber optic devices: fiber multiplexers, fiber attenuators, fiber splitters, fiber TAPs and fiber terminators. Since their development, passive devices have grown from simple splitting devices to sophisticated components capable of controlling individual wavelengths. They don't add gain or require power, but they decide how efficiently, cleanly, and safely light moves through your network or laser chain. This guide blends clear definitions with engineer-grade selection criteria, with a. Passive fibers are optical fibers without laser-active dopants in the fiber core.