  Generation of high-repetition-rate, femtosecond, soliton pulse trains through
dual-wavelength pumping of a dispersion-decreasing fiber is studied
numerically. The achievable shortest pulse width is found to be limited by
third-order dispersion that has a significant effect on the pulse-compression
dynamics. The output wavelength is red shifted because of intrapulse Raman
scattering and depends heavily on third-order dispersion, whose positive values
lead to the most red shifted solitons (>25% of the input pump center
wavelength). The proposed scheme allows the generation of ultrashort pulse
trains at tunable high repetition rates with a wide range of output wavelengths
and pulse durations through dispersion engineering. The resulting frequency
combs extend over a wide bandwidth with a tunable spacing between the comb
lines.
