Figure 7.

The process of calculating β4.


## Table 2. The average.

fibers has its special average β<sup>4</sup> which reveals the characteristic of fibers. These values are similar to those experiment results in highly nonlinear fibers [35, 36]. Although we take the higher-order nonlinear effect δγ into account which upgrades

the pulse's symmetrical split and redshift, the items is <sup>∂</sup> j j <sup>u</sup> 2 u � �=∂<sup>t</sup> and

iδγ exp ð Þ �2αz j j u 2 u have a very tiny contribution to β4, only 10�<sup>26</sup> ps4 /km quantity order for the typical SMF. Here, the impact of δγ is hidden by the relative strong β2.
