CC BY 4.0 UnportedBoonzajer Flaes, Dirk E.Stopka, JanTurtaev, Sergeyde Boer, Johannes F.Tyc, TomášČižmár, Tomáš2023-03-062023-03-062018https://oa.tib.eu/renate/handle/123456789/11687http://dx.doi.org/10.34657/10720Light transport through a multimode optical waveguide undergoes changes when subjected to bending deformations. We show that optical waveguides with a perfectly parabolic refractive index profile are almost immune to bending, conserving the structure of propagation-invariant modes. Moreover, we show that changes to the transmission matrix of parabolic-index fibers due to bending can be expressed with only two free parameters, regardless of how complex a particular deformation is. We provide detailed analysis of experimentally measured transmission matrices of a commercially available graded-index fiber as well as a gradient-index rod lens featuring a very faithful parabolic refractive index profile. Although parabolic-index fibers with a sufficiently precise refractive index profile are not within our reach, we show that imaging performance with standard commercially available graded-index fibers is significantly less influenced by bending deformations than step-index types under the same conditions. Our work thus predicts that the availability of ultraprecise parabolic-index fibers will make endoscopic applications with flexible probes feasible and free from extremely elaborate computational challenges.enghttps://creativecommons.org/licenses/by/4.0550530Computational challengesEndoscopic applicationsGraded-index fibersGradient index rod lensImaging performanceMulti-mode waveguidesMultimode optical waveguidesRefractive index profilesArticle