e the automatic gain con- trol and the automatic power control. They are control loops that stabilize the saturated gains or the output optical power, respectively, by acting on different amplifiers param- eters (like the pump power or the position of an output variable attenuation). One of the considered devices is also equipped with a network manager interface that means that it is also designed to work alone in a system amplification site SO that it has to be recognized by the element manager as a network element. 4.3.3 Raman Fiber Amplifiers Raman amplifiers are based on the stimulated Raman emission creating a Raman gain in a medium where an optical pump has created population inversion between the Raman levels [58]. Differently from EDFAs, Raman amplifiers exploit a nonresonant incoherent phenom- enon; as a matter of fact the Raman gain curve is very wide (compare Figure 4.9). For the same reason, while erbium-doped fibers gain is located in a specific wavelength range, depending on the erbium ion transitions, the Raman gain bandwidth only depends on the optical pump wavelength; thus, Raman gain can be obtained at whatever wave- length, only assuming that a suitable pump laser is available. Also shaping the Raman gain spectrum is in principle an easy task. As a matter of fact, if the pump is not monochromatic, but is composed of an opportune set of lines, the result- ing Raman gain bandwidth can be shaped as suitable for the application [59]. Technology for Telecommunications: Optical Fibers, Amplifiers, and Passive Devices These characteristics of Raman amplifications make this technique quite useful in trans- mission systems, not to replace, but to complement EDFAs. However, besides these advantages, Raman amplifiers also pose a set of important chal- lenges that caused the fact that, even if researchers were working on Raman amplification far earlier than on erbium-doped fibers, the presence of Raman amplifiers installed in the field is quite recent. The first issue is the low pumping efficiency characte