In this article the basic information about the whispering gallery modes (WGM) concerning questions of mathematical description, properties of whispering gallery resonators (WGR), methods of radiation coupling into resonators, resonators manufacture methods, and possible applications in the field of optical communication systems is considered. A brief history of WGM discovery is presented, and the main properties and characteristics of such resonators and modes are discussed. The main goal of this work is to survey the field of WG modes that is becoming more and more attractive due to their interesting and exciting properties with accordance to possible applications in passive optical components development as well as in design of active components such as lasers and modulators.
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.