Method of characterizing a light beam having the steps of: a) disposing the input ends of N >3 optical fibers on the path of the light beam, in such a way that a respective portion of the beam is coupled and propagates in each optical fiber and is emitted from its output end so as to form a respective secondary beam; b) introducing an angular spectral dispersion into the secondary beams by means of at least one dispersive element; c) propagating the dispersed secondary beams in such a way that they overlap to form an interferogram; d) acquiring an image of the interferogram; and e) extracting from the image of the interferogram an item of information relating to the spatial variation of the phase of the light beam at a plurality of wavelengths. Device for the implementation of such a method.