In the nonlinear optical fiber, soliton is a pulse envelop that formed under the balance of group velocity
dispersion(GVD) and self-phase modulation(SPM). It has the transmission characteristic that the pulse shape and
amplitude are steady. The GVD causes the pulse stretch, but the SPM induces the high frequency elements to
accumulate step by step, and the soliton pulse change steep. The two kind of opposition factors unit in together,
mutually balances can maintain the pulse shape stabilization invariable.
Along with the soliton research, it extends from picosecond (ps) to femesecond (fs). High order dispersion, in
particular the third order dispersion (TOD) influences the soliton transmission very large. The high order
dispersion is studied by the split step Fourier method (SSFM) numerical analysis the modified high order
nonlinear Schrödinger equation(HNLSE). The results indicate that the TOD and the fourth order dispersion(FOD)
can all affect the quality of the telecommunication. And the TOD plays the main role. It causes the pulse bottom
vibration in one side, causes the pulse to stretch and to form vibration belt. The FOD causes the soliton bottom
vibration in two sides, it causes the pulse stretch and the spectrum appears side lobe.