Spatio-temporal transformation of the femtosecond laser pulses at 1550 nm wavelength in c-Si is observed using the methods of time-resolved microscopy. The temporal dynamics of the pulse manifests itself both in widening of the frequency spectrum and in the change of on-axis time-width. It is shown, that along with Kerr effect, two-photon absorption also contributes to the temporal reshaping of the laser pulse. Despite the fact that absorption length for green light in c-Si is as small as 1 µm, generation of visible third harmonics was also observed in c-Si.