Optical Fibre Refractive Index Reconstruction from Mode Near Field

ABSTRACT. A novel and accurate refractive index profile synthesis method for optical fibres is developed using knowledge of the fundamental or higher order mode near field. This fundamental method is based on inverse transmission line principles. From Maxwell’s equations, we derive a transmission line equivalent circuit for a circularly symmetric optical fibre with arbitrary refractive index. We demonstrate how to use this model to carry out the inverse problem of synthesis of the refractive index profile from mode near field data. We apply this method to construct waveguides supporting unusual near field patterns, and the accuracy of the reconstructed refractive index profile is examined numerically.