Interferometry of optical vortices in the presence of spatial phase noise

A method for recording interferograms of optical beams with orbital angular momentum (OAM) is proposed. Interferograms are formed due to interference of the zero and one of the first orders of beam diffraction when an additional diffraction grating is added into the optical scheme. The noise robustness of such a detection method has been experimentally and theoretically investigated using the addition of OAM beams with two-dimensional phase noise. The Gaussian distribution was used to describe the phase noise. The magnitude of its standard deviation $\sigma$ varied during measurements. For these specific conditions of our experiment, the limiting value $\sigma$ was determined, which makes it possible to register the value of the OAM according to the criterion $S/N$=3.