Erbium-doped fiber is a type of optical fiber that has been infused with the rare earth element erbium. This doping process enhances the fiber's ability to amplify light signals, making it essential for long-distance telecommunications. The unique properties of erbium allow it to efficiently amplify specific wavelengths of light, particularly in the 1550 nm range, which is commonly used in fiber optic communication. These fibers are widely used in fiber optic networks to boost signal strength and improve data transmission over long distances. By using erbium-doped fiber amplifiers (EDFAs), network operators can maintain high-quality signals without the need for frequent regeneration, thus increasing the efficiency and reliability of communication systems.