Fiber optic adapters, also known as couplers, play a crucial role in fiber optic networks by providing a connection point between two fiber optic connectors. A fiber optic coupler is a device used to couple light from one or several input fibers into one or more fibers or from free space into the fiber. How are fiber couplers fabricated? Common. Enter the Fiber Optic Coupler – a fundamental, yet often overlooked, passive device that is crucial for splitting, combining, or distributing optical signals. The device allows the transmission of light waves through multiple paths.