Speckle structure of an optical field in multimode fiber waveguides

An investigation is made of the statistical properties of an optical field with a speckle structure in multimode fiber waveguides. Asymptotic formulas are obtained for the spatial correlation function of the field. This function is used to obtain expressions for the statistical average density of dislocations in the wavefront of the field distributed over a transverse cross section of a waveguide with an arbitrary refractive index profile. It is shown that the dislocation density is an oscillatory function of the transverse coordinate. A study is also reported of the dependence of the dislocation density on the refractive index profile and on the conditions of excitation of a waveguide.