A coupler can be used as a splitter to couple out some portion of the light circulating in the resonator of fiber laser, for example. Directional 2 × 2 couplers (see Figure 1) are usually used for such purposes. The same kind of device is useful in fiber interferometers, also for combining two. Definition: fiber devices for coupling light from one or several input fibers to one or several output fibers, or from free space into a fiber Categories: fiber optics and waveguides, photonic devices Concept tree: DOI: 10. We consider in this tutorial two-channel directional couplers, which. Video 1. 1 This animation provides an introduction to the mechanism of the FiberPort and shows how the FiberPort can be used as a collimator. For more information, please see the Alignment Procedure tab.