In this paper physical effects caused by macro- and micro bends of optical fiber including additional mode-dependent loss, mode coupling and spurious mode excitation in fiber MDM-system are considered. The effects described below can dramatically decrease capacity and maximum data rate in such systems because of inevitability of fiber bends due to system exploitation thus making MDM-system commercialization much more difficult and expensive. Mathematical approach used to describe these effects and applied in the simulation model is based on well- known refractive index profile approximation  of bent step-index fibers and mathematical field coupling model .
In this paper we introduce a novel method for mode-coupling compensation in MDM systems based on the adaptive optics. This approach is intended to minimize significantly the computational complexity required for digital signal processing, because only computation of diffraction optical element transmission function is performed and no real time signal processing is required to compensate for intermodal interference. Therefore, existing challenges of MIMO MDM systems, such as DSP performance limits and increasing power consumption, might be overcome.