V. F. Dubrovin

The method of definition presented in article modes structure of field at an end face of a round optical wave guide across the field in a far zone was developed within the limits of works on creation of a equipment complex for diagnostics and detection of defects at details of aviation techniques, and also definition of a spectrum of their mechanical resonances in a wide strip of frequencies by methods of coherent optics. The set specifications on equipment have caused necessity of use as the channeling laser radiation of systems and radiators optical wave guides. Now the scope of optical wave guides quickly extends as in scientific researches, so various areas of techniques. Thus, comprehensive investigation of real electrodynamics characteristics of various type optical wave guides is necessary. The offered method is represented actual. Known methods of the analysis of a field in a radiators far zone and its communication with the near are demand expenses of considerable time for calculations. Their use in a combination to experimental data about character of radiations field for definition modes structures on the radiating aperture in most cases is inconvenient. The purpose of the present work is reception of convenient, not demanding big computing expenses of a method of definition modes field structure at an end face of a round optical wave guide on a known field in a far zone by means of use a system of wave guide own functions as basic. It is supposed, that the field at a target end face of a wave guide is limited by a core and, in neglect following waves, it is represented the final sum of own functions - directed fashions. Fields of fashions are approximated by Bessel functions that are quite correct for the majority of optical wave guides. The method described in article is updating of an existing method partial diagram-s, at which field at an end face it turns out in the form of decomposition on system of own functions of a wave guide. It is essential, that a number in the offered method contains final number of nonzero members. The simple formula for definition modes field structure at an end face of an optical wave guide across the field in a far zone is as a result received. To find each of peak factors of fashions it is necessary to calculate one integral from function of one variable. It provides a considerable prize in computing expenses and presentation of results in comparison with known methods. Advantages of the described method are caused by that finiteness of a set of directed modes and a kind of own functions of a wave guide in advance is considered.