Fiber amplifiers are optical amplifiers based on optical fibers as laser gain media. In most cases, the gain medium is a glass fiber doped with rare earth ions such as erbium (EDFA = erbium-doped fiber amplifier), neodymium, ytterbium (YDFA), praseodymium, or thulium. An illustration of the effective gainis given below. Typical fiber cables experience a loss of about 0. An optical amplifier is a device that amplifies an optical signal directly, without the. With the increase in communication traffic, the importance of optical amplifiers such as EDFAs (erbium-doped fiber amplifiers) that can directly amplify optical signals without converting them into electrical signals has been widely deployed in traditional backbone optical transmission networks.