  A phenomenological model for spectral broadening of incoherent light in
silica fibers via self-phase modulation and dispersion is presented, aiming at
providing a qualitative and readily accessible description of incoherent light
spectral broadening. In this model, the incoherent light is approximated by a
cosine power-modulated light with modulation parameters depending on the
coherent time and the dispersion in fibers. A simple and practical method for
spectral broadening predictions is given and demonstrated by both the
straightforward NLSE-based numerical modeling and series of experiments
including narrowband and broadband incoherent light in passive fibers and fiber
amplifiers.
