An ultra-broad spectrum over the range from 480 to 900 nm is experimentally generated by induced-phase modulation (IPM) of two 120 fs intense optical pulses copropagating in a 3-mm single-mode fused-silica fiber for the first time to our knowledge, The center wavelengths of the two pulses are 640 nm and 795 nm. respectively. The Fourier transform of this spectrum yields a transform limited 4 fs optical pulse. This IPM-induced spectrum broadening method opens the way to monocycle optical pulse generation in the near future, (C) 1999 Elsevier Science B.V, All rights reserved.