Dichroic couplers can be used to combine a pump and a signal input for a fiber amplifier, or to remove residual pump light after the amplifier. For high-power fiber lasers and amplifiers, one often needs pump couplers with multiple inputs, combining the outputs of several high-power. At a fundamental level, a fiber optic coupler is a device that distributes or combines optical signals (light) between two or more optical fibers. In simple terms, they serve as the 'traffic managers' of the light that carries information within the fiber optic network. It functions by dividing a single incoming light path into multiple outgoing paths, or by combining light from several input paths into a single output fiber. A fiber optic coupler is a device that can distribute the optical signal. What are some common uses of fiber couplers in fiber optics, including fiber lasers? What are dichroic couplers and how are they used in fiber amplifiers? What is the principle of evanescent wave coupling? What factors influence the coupling strength and wavelength sensitivity in fiber couplers?.