Fiber optic amplifiers address a fundamental challenge in optical communication: signal attenuation. As light travels through fiber cables, it loses intensity due to scattering and absorption. Without amplification, signals degrade over long distances, limiting transmission ranges. Booster (power) amplifiers: Boost power into transmission fiber, low NF, high Psat. An illustration of the effective gainis given below. The. Erbium-doped fiber small-signal amplifier (PA, Pre-Amplifier) is dedicated to amplifying weak optical signals in the range of -45dBm ~ -25dBm, the typical small-signal gain is as high as 35~45 dB, and it has a low noise figure. Every network has a "loss budget".