An optical attenuator, or fiber optic attenuator, is a device used to reduce the level of an optical, either in free space or in an. The basic types of optical attenuators are fixed, step-wise variable, an. Optical attenuators are commonly used in, either to test power level margins by temporarily adding a calibrated amount of signal loss, or installed permanently to properly match transmitter. The power reduction is done by such means as absorption, reflection, diffusion, scattering, deflection, diffraction, and dispersion, etc. Optical attenuators usually work by absorbing the light, like absorb extr.