  This letter is to pave the way towards the demonstration of spatiotemporal
similariton pulses evolution in passive multimode fibers with Raman
amplification. We present numerically these issues in a graded-index and
step-index multimode fibers and provide a first look at the complex
spatiotemporal dynamics of similariton pulses. The results showed that the
similariton pulses can be generated in both multimode fibers. The temporal and
the spectral evolution of the pulses can be characterized as parabolic shapes
with linear chirp and kW peak power. By compressed these, high energy
femtoseconds pulses can be obtained starting initial picoseconds pulses.
Spatial beam profile could be preserved in both multimode fibers under the
predominantly excitation of the fundamental mode. Specifically, Raman
amplification and similariton pulses generation in graded-index multimode fiber
improves the spatial beam cleaning process under the different initial
condition.
