Used as a dopant in optical fibers for amplifiers in telecommunications, particularly in erbium-doped fiber amplifiers (EDFAs) that boost signal strength in long-distance fiber-optic networks. Also employed in the production of specialty glasses and ceramics with unique optical properties. Serves as a source of erbium ions in research and development of luminescent materials and solid-state lasers. Applied in some medical lasers for dermatological treatments due to its emission in the infrared range. Used in nuclear reactors as a neutron absorber in control rods because of erbium’s high neutron capture cross-section.