Sub-picosecond chirped pulse propagation in concave-dispersion-flattened fibers

We propose the sub-picosecond chirped soliton pulse propagation in copcave-dispersion-flattened fibers （CDFF）. The effects of pulse characteristics and the fiber dispersion parameters on propagation characteristics of the chirped soliton pulse are numerically investigated in the CDFF by the split-step Fourier method （SSFM）. The unchirped soliton pulse can stably propagate with unchanged pulse width in the CDFE The temporal full width at half maximum （FWHM） of the chirped soliton performs a damped oscillation with the increase of propagation distance. The period and amplitude of the oscillation increase with the increase of the chirp parameter ｜C｜. The effect of high-order dispersion （β3-β6） on soliton propagation characteristics can be neglected. The soliton pulse slightly broadens with the increase of propagation distance and still maintains soliton characteristics when the fiber loss （ATT） is further considered. The variation of root-meansquare （RMS） spectral width with propagation distance is opposite to that of the temporal width. The output spectrum of soliton has a single peak for the unchirped case, while has multi-peak for chirped case. The temporal width of the soliton obviously increases with the increase of the initial width, decreases with the increase of dispersion peakD0 of the fiber, and slightly increases with the decrease of dispersion coefficients k1 and k2 of the fiber.