Flatly broadened supercontinuum spectrum generated in a dispersion decreasing fibre with convex dispersion profile

Dispersion design in a single-mode fibre is investigated experimentally and numerically for generating a supercontinuum with a flatly broadened spectrum. It is found to be important both that group velocity dispersion is a convex function with two zero-dispersion wavelengths and also that it decreases with fibre length. A calculated spectrum explains well that obtained experimentally. The mechanism of the spectral evolution of supercontinuum is examined