  A method to probe the guiding characteristics of waveguides formed in
real-time is proposed and evaluated. It is based on the analysis of the time
dependent light distribution observed at the exit face of the waveguide while
progressively altering its index profile and probed by a large diameter optical
beam. A beam propagation method is used to model the observed dynamics. The
technique is applied to retrieve the properties of soliton-induced waveguides.
