Erbium (Er) is a chemical element that has the atomic number 68 in the periodic table of the elements. It belongs to the rare earth
metals. Erbium is used in optical amplifiers such as the EDFA amplifier with erbium-doped glass fibers and for dopingresonators
in solid-state lasers. In components for optical data transmission and light wave generation, erbium is used in combination with silicate and phosphate glasses. The emission wavelengths of erbium are 0.55 µm, m and 2.7 µm.