Spatial coherence of the optical field in multimode waveguides

A quasiclassical theory of spatial correlation of the optical field in dielectric waveguides of circular cross section is developed. Quasiclassical expressions for the spatial correlation function and for the field intensity in a waveguide with an arbitrary refractive index profile are obtained on the assumption that there is no intermode correlation. An analytic explanation is given of the numerically predicted oscillations of the intensity in the near field of a multimode waveguide excited by a spatially noncoherent light source. A study is made of the influence of leaky waveguide modes on the spatial coherence and intensity of the field.