Optical couplers are not like electrical devices. A detector takes in the signal instead. An optocoupler, also known as photocoupler or opto-isolator, is a device which can transfer an electrical signal across two galvanically-isolated circuits by way of optical coupling. Unlike transformers or capacitors, which can only transfer AC signals across the isolation barrier, optocouplers can. 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 diode bars. These devices work both ways, which helps strong network communication.