Research on evolution region of self-similar pulses in a dispersion-decreasing fiber

The relationship between the self-similar propagation region for single pulse and oscillation region for a pair of self-similar pulses are first investigated in our paper. By introducing self-similar coefficient F and RMS width ratio K , we find that self-similar propagation region starts from z = 1.8 L D to z = 18 L D while F ≤ 10%. The optimum output of self-similar pulse is also achieved when F and K reach a minimum value simultaneously at z = 3.5 L D . The sinusoidal fit oscillation region of self-similar pulse pair ranges from 5/8 L D to 2 L D while F varies from 40.27 to 7.99%, and the dark soliton fit oscillation region ranges from 2 L D to 6 L D while F varies from 7.99 to 5.32%, indicating that the sinusoidal fit oscillation region almost occurs before the pulses enter the self-similar propagation region and the dark soliton fit oscillation region occurs within the self-similar pulse propagation region. Furthermore, the oscillation characteristics of interacting pulses are also studied numerically by using split-step Fourier method. The results are beneficial in Dense Wavelength Division Multiplexing transmission system which is in heavy demands of light source in wide-range wavelength.