A fixed optical attenuator is a fiber optic component designed to reduce the intensity of an optical signal by a set amount. It is used when the required signal reduction is already known and does not need to change during operation. You can think of it as a permanent “volume reducer”. Fiber-optic attenuators are a specific type of optical attenuators which are used in fiber optics, e. F-ADAT-13-03-55 Fiber Optic Attenuator, Fixed, 1310 nm, 3 dB, FC/APC Connector.