Erbium is a rare earth element and a member of the lanthanide series in the periodic table. It has the atomic number 68 and the symbol “Er”. Erbium is relatively stable in air and water but can react with acids and other halogens. It is used in various applications such as nuclear reactor control rods, fiber optic amplifiers, and as a colorant in glass and porcelain. Erbium-doped fiber amplifiers are widely used in modern communications networks to amplify signals on long-haul fiber optic cables.