Experimental mode coupling analysis in optical waveguides for sensor and component optimization

A computer controlled mode coupling analyser is conceived and described in detail to characterize and to analyse mode coupling in all known kinds of cylindrical, multimode, step index, optical waveguides (CMSIOWs) by experimental measurement. These waveguides can be present in many ways like simple fibres, multimode fibre-optic sensors (MFOS) or other optical components like couplers or modulators. The computer processed results of measurements lead to transfer matrices and modulation transfer matrices. The transfer matrices describe the light distribution in the far field of these waveguides depending on the direction and power of the light that is injected into it. By visualizing the modulation transfer matrices in the form of mesh diagrams, the influence of external physical parameters, like a measured variable, on the mode coupling mechanisms inside CMSIOWs can be shown directly. The computer controlled mode coupling analyser will make the optimization of MFOS more efficient and, moreover, it will ease modelling of CMSIOWs and define their properties. The potential field of applications for the mode coupling analyser will be in engineering and optimization of intrinsic multimode fibre-optic sensors and their components.