Self-Phase Modulation（SPM） in optical fibers tends to result in the spectral broadening of optical pulses.In this paper

SPM effect is simulated in Optisystem by adjusting the parameters of fibers and optical pulses

the influences of such parameters as fiber length

peak power

pulse shape and initial chirps on SPM spectrum are analyzed in detail and a phenomenon of spectral narrowing at the fiber output end caused by the negative initial chirp is observed.