Optical attenuators can take a number of different forms and are typically classified as fixed or variable attenuators. [dead link] Fixed optical attenuators used in fiber optic. An optical attenuator is a passive device that is used to reduce the power level of an optical signal. The attenuator circuit will allow a known source of power to be reduced by a predetermined factor, which is usually expressed as decibels. Key requirements include minimal effect on the beam profile, low wavelength and polarization dependence, and sufficient power handling capability.