Waveguide dispersion distortion parameter

Fig. 14-10 (a) The distortion parameter for the fundamental modes of clad power-law profiles and (b) the values of the fiber parameter at which waveguide dispersion vanishes, the q= oo line corresponding to the value for the step profile. 

We showed in the previous section that the distortion parameter D can have a zero for values of K of practical interest only if q > 2. Consequently, the vanishing of waveguide dispersion depends primarily on profile shape. 

If 0 < V < 2.592 the fiber is single moded. The pulse transit time of Eq. (11-36) is inversely proportional to the group velocity, and pulse spreading due to waveguide dispersion is proportional to VAD = A/where D is the scalar distortion parameter. The expression for D in Table 15-2 is plotted as the solid curve in Fig. 15-1 (d). Compared with the dashed curve, calculated numerically, the maximum relative error is 9.6% at F = 2.9, while at K = this error is 9.4%. There is no zero of waveguide dispersion. 

We show in Table 15-3 that there is only a very small error between the approximate and exact values of U for the fundamental mode, calculated at the exact cutoff of single-mode operation for each profile [7]. The distortion parameter of Table 15-2 is plotted as the solid curves in Fig. 15-2(b) for the m = 2 and step profiles, together with the dashed curves for the exact values [7]. If Fj denotes the values of V for which there is no waveguide dispersion, i.e. D = 0, then... 

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