Fig. 5

Experimental spectral evolutions of single-peak spectra. Experimental optical spectra in a linear scale (A, B, C) and in a logarithmic scale (D, E, F). (A) and (D): 0.11 nm initial FWHM linewidth. (B) and (E): 0.23 nm initial FWHM linewidth. (C) and (F): 1.47 nm initial FWHM linewidth. The input spectra, the broadest spectra and the eventual stable spectra are shown as blue, red and orange lines, respectively. G, H Spectral broadening factors dependence on the propagation distance, calculated using (G) FWHM linewidth and (H) RMS linewidth. Note that the input power P₀ is also fixed at 1.2 W in all the experiments