Fiber couplers, inline photodiodes, WDMs, combiners, circulators, and optical switches provide fundamental building blocks for fiber-based optical circuits. Thorlabs offers a wide variety of collimation and coupling components that can be used to effectively collimate or couple light out of and into FC/PC, FC/APC, or SMA terminated fiber. Light from an input fiber can appear at one or more outputs. Here you'll find the full range of products available at LASER COMPONENTS. The device allows the transmission of light waves through multiple paths. Fiber optic couplers can either be passive or. Fiber optic couplers are optical devices that connect three or more fiber ends, dividing one input between two or more outputs, or combining two or more inputs into one output.