Lecture
This lecture covers rare earth doped fiber amplifiers, which use fibers doped with elements like erbium to amplify signals. The properties of these amplifiers depend on the dopant used, such as erbium, holmium, neodymium, thulium, or ytterbium. Erbium doped fiber amplifiers are particularly popular due to their operation at 1550 nm wavelength, achieved by doping the fiber core with Erbium Er3+. The lecture explains the energy levels of erbium atoms, the operation of erbium doped fiber amplifiers, and the factors affecting their gain spectrum. It also discusses the pumping choices for these amplifiers, including forward and backward pumping with 980 nm or 1480 nm lasers. The advantages of erbium doped fiber amplifiers, such as high gain efficiency and low crosstalk, are highlighted, along with their limitations like sensitivity to traffic fluctuations and size.