 possibly Telecommunication Networks TABLE 4.1 Typical Values of the Parameters of a Step Index Single-Mode Transmission Fiber Attenuation (dB/km) Core refractive index (adim.) Effective mode radius (um) Dispersion parameter (ps/nm/km) Dispersion coefficient (ps2/km) Third-order dispersion coefficient (ps3/km) Birefringence (m-1) PMD (ps/ k/ mm) Random mode coupling characteristic length (m) Real part of third-order susceptibility (W-1) Xxxxx 1.56 X 10-19 Nonlinear coefficient (W-1 km-1 Brillouin gain coefficient (m-1 W-1) 6.02 X 10-12 Brillouin gain bandwidth (MHz) Raman gain coefficient (m - 1 W-1) 7x 10-15 All values are at a=1.55pm. including both second and third transmission window, nonzero dispersion fibers are gen- erally realized to move the zero dispersion wavelength in between the two transmission windows. Different index profiles corresponding to different categories of fibers for long-haul transmission manufactured by the main fiber vendors are represented in Figure 4.4. In all the cases represented in the figure, the study of the structure-guided modes dem- onstrate that two degenerate fundamental modes of the LP type can propagate in the fiber and that the spatial profile of this mode is Gaussian with a good approximation, exactly as in a step index fiber. The variance of the field mode shape is different for different fibers causing a difference in the field confinement. As we will see, this will have an impact on the efficiency of nonlinear effects during field propagation. Refraction Cladding index Depressed cladding W profile A profile FIGURE 4.4 Segmented Different possible refraction index profiles for dispersion managed fibers. Radius Technology for Telecommunications: Optical Fibers, Amplifiers, and Passive Devices Large slope Wavelength (nm) FIGURE 4.5 Dispersion characteristic versus wavelength for different dispersion-managed fibers. The dispersion curve of a set of "managed dispersion" fibers is reported in Figure 4.5, and some important parameters of commercial fibers are summarized in