s almost cancels, generating a pulse width decrease. This interpretation of the pulse shrink is confirmed by the fact that the minimum relative pulse width arrives near 0.5 and never goes below this value. The SPM-induced broadening superimposes with the broadening due to fiber disper- sion. In the normal dispersion regime, the two effects have the same sign and the observed pulse broadening is greater than that due to dispersion alone; on the contrary, in the anom- alous regime the two effects have different signs and the overall broadening is smaller than that due to dispersion. This effect is very important in transmission systems. When the Kerr effect theory was consolidated, it was also discovered that, giving to the intensity of the field a particular shape, the linear and nonlinear effects completely cancel and the pulse propagates without broadening through thousands of kilometers of fiber. These particular pulses are known as solitons and in a first moment they were regarded as the key to design very high-capacity and ultra-long-haul systems [18,19,22]. The propagation dynamics of solitons however is quite complex: since a single pulse travels unchanged but for attenuation, and since the zero broadening condition is reached only for a precise value of the input power, a soliton can be realized only in a first approxi- mation in a real fiber. Even if a single soliton does not broaden, a random train of nearby solitons (representing a random string of bits) is affected by a sort of jitter due to the attraction between adjacent pulses. Moreover, if WDM is used, more jitter comes out due to the interaction between frequency adjacent channels. Last but not least, perfect nonlinear and linear chirp compensation creates perfect phase matching among WDM channels belonging to the same comb, maximizing the dangerous nonlinear interchannel crosstalk. Technology for Telecommunications: Optical Fibers, Amplifiers, and Passive Devices A great amount of research has been devoted to solve these problems, producing brill