Optical amplifiers enhance optical signals without converting the signal into electrical form. As the demand for wider bandwidth grows, there is a requirement for more efficient and reliable optical amplifiers. This is the same requirement that is in demand for long transmission lengths, i.e., amplifiers developed to support dense wavelength-division multiplexing (DWDM). Thus, optical amplifiers have become an essential component in both (1) long-haul and (2) higherdata-transmission systems.