Erbium is a chemical element in the lanthanide series, with symbol Er and atomic number 68. Optical fibers doped with erbium, can amplify light in the 1550 nm region when pumped at around 980 or 1480 nm by an external light source. The 1550 nm wavelength is important for optical communications because standard singlemode optical fibers have minimal loss at this particular wavelength. This process results in an unusually mechanically simple laser optical amplifier. Fiber amplifiers are used to support dense wave length division multiplexing (DWDM) and to expand to the other wavelength bands supported by fiber.