Method of characterizing a light beam (FL) comprising the steps consisting in: a) disposing the input ends (EE1-EE11) of N>3 optical fibres (F01-F011) on the path of said light beam, in such a way that a respective portion of said beam is coupled and propagates in each optical fibre and is emitted from its output end (ES1-ES11) so as to form a respective secondary beam; b) introducing an angular spectral dispersion into said secondary beams by means of at least one dispersive element (RD); c) propagating the dispersed secondary beams in such a way that they overlap to form an interferogram; d) acquiring an image of said interferogram; and e) extracting from said image of said interferogram an item of information relating to the spatial variation of the phase of said light beam at a plurality of wavelengths. Device for the implementation of such a method.