They are usually installed at the transmit end of active modules, such as OTU and OSC boards, to prevent the downstream receiver modules from being burnt due to excessively high output optical power. The disadvantage is that the attenuation value cannot be adjusted. An optical attenuator, or fiber optic attenuator, is a device used to reduce the power level of an optical signal, either in free space or in an optical fiber. Why Do We Need the Optical Attenuator? The receiver of an optical module has. Transmitter power (TP) = 3dBm Receiver maximum optical input power (MP) = -6dBm Total losses (TL) = 5dB Minimum attenuation required = MP + TL – TP = -6dBm + 5dB – 3dBm = – 4 dB At a minimum, a 4 dB attenuator is required. Fiber-optic systems use a wide variety of relays, switches, amplifiers, and other devices that are connected by fiber-optic cables. Attenuators are extensively used across.