Fiber optic attenuators are used to suppress signal strength in fiber optic networks by inducing variable or fixed losses. When inserted in a network, a fiber optic attenuator reduces the power of the input before delivering it to the load. They are also employed in testing the dynamic range and the linearity of photo detectors and photo sensors. Fiber optic attenuators utilize various methods to induce variable or fixed losses. These include microbends, air gaps, electro-optic modulators, and acousto-optic modulators.

An air gap causes a change in the refractive index resulting in a reflection. Microbends consist of sharp curvatures and minute local axial displacements. These displacements are on the order of microns. Microbending results in mode coupling and radiant loss. In the case of electro-optic modulators, an electric field is used to interfere with the characteristics of an optical signal. Acousto-optic modulators utilize sound waves to alter the signal characteristics of an optical signal. Some of the signal characteristics that are affected by such interferences include frequency, amplitude, and phase of the optical signal going through the acousto-optic medium.

Fixed fiber optic attenuators suppress the optical power of a signal as it approaches a node to a suitable level. Communication links that employ fixed fiber optic attenuators include CATV, LAN, and a variety of telecommunications networks. On the other hand, variable fiber optic attenuators are engineered to offer a variety of attenuation values. This class of attenuators is mostly used for testing and measurement purposes.