“…Optical fibres are most appropriate for spectral broadening by selfphase modulation because high intensities in a small spot are maintained over long distances [4][5][6][7][8]. In fibres the spectral broadening may be extended by cross-phase modulation [4,5], modulation instability [4,5,9], stimulated Raman scattering [4,5], stimulated four-photon mixing [4,5,[10][11][12][13] and parametric amplification [4,11,14]. Strongly broadened spectral pulses in monomode fibres [7,12,13,15,16] and multimode fibres [17,18] have been reported.…”