Modal power decomposition of light propagating through multimode optical fiber

The structure of the light field propagating through multimode fibers is of great interest for creating fiber sensors and other applications. Here, using only one linear polarized component of spatial-intensity profiles in near- and far-field regions of a beam emitted from the fiber, we propose a method for the modal power decomposition. As a simple example, modal power decomposition has been done for optical fibers with a step-like index profile. Experiments have been carried out for the fiber with V=54. The method can be used for fibers with any known refractive index profile, core diameter, indices of the core and cladding.