Starting from the de Gennes theory of director fluctuations in nematics, we report on a model of the spatialfluctuations in nematicon propagation. We demonstrate that, when the long-range correlation that characterizesnematic liquid crystals is taken into account in the thermal noise, it is possible to account for the spatial oscillationsand propagation losses experienced by nematicons. Increasing the power of the nematicon, the oscillationamplitudes increase and the propagation losses decrease. The nematicon is then more strongly confined anddeviates more, but is less scattered by the thermally induced perturbations of the refractive index. All the resultsare in good agreement with the experimental observations.
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