 Table 4.2. The various performances are compared with the performances of a standard step index fiber. The first dispersion-managed fibers to be produced were DS fibers, where the disper- sion curve is shifted toward higher wavelengths SO that the zero dispersion wavelength is moved around 1.5 um. These fibers were designed and deployed in the period in which long-haul single- channel systems were designed in order to decrease chromatic dispersion and increase the transmission reach. With the introduction of dense wavelength division multiplexing (DWDM) systems, this class of fibers was practically abandoned, due to the fact that having the zero dispersion wavelength in the third transmission window causes the maximization of nonlinear chan- nel crosstalk due to the channel phase matching. In order to allow high channel count DWDM systems to be deployed and contemporary to decrease as much as possible the value of dispersion, nonzero dispersion fibers were designed. TABLE 4.2 Comparison between the Properties of a Set of Fibers with Different Index Profiles Dispersion Dispersion Index Parameter Slope (ps/ Attenuation Effective Acronym Profile (ps/nm/km) nm2/km) (dB/km) Area (um2) Step index 16 to 18 Dispersion shifted Segmented Nonzero dispersion + Segmented 3 to 5 0.045 Nonzero dispersion - Segmented -3 to -2 Large effective area Segmented 3 to 6.5 Intermediate dispersion Segmented 6 to 9 All values in the table that depend on wavelength are reported at a 1.55 um. Telecommunication Networks In this kind of fibers, the dispersion curve is shifted to move the zero dispersion wave- length either in between the second and the third window or beyond the third window around 1570 nm. In the first case, the fibers are called NZ+ and in the second NZ-. Using these fibers allows avoiding zero dispersion in the transmission bandwidth while reducing the average dispersion. Moreover, especially in the case of NZ-, the fiber design can be performed to achieve a greater effective mode ratio to decrease nonlinear effects. This