Theoretical design of optical fibers with protection of linear operation mode against external thermal and electric disturbances

In this study, we derived analytical relations for designing a step index optical fiber that operates in the linear mode and remains insensitive to external thermal and electrical fluctuations. These relations are based on the fragments of cloaking theory previously developed for two-dimensional structures using the approaches of transformation optics. We obtained and analyzed the radial dependence of the refractive index in both the cladding and core regions under thermal disturbances. An expression for the nonlinear thermal coefficient of the materials of the both regions was also derived, ensuring opacity to thermal fluctuations for a given fiber geometry. The analytical results were validated using MATLAB simulations. The results show that, in steady-state mode, both thermal and electric fields bypass the fiber smoothly, without disturbing the surrounding medium.