  We present a detailed theoretical analysis on image transmission via a single
multimode fiber (MMF). A single MMF imaging model is developed to study the
light wave propagation from the light source to the camera, by using free-space
Fourier optics theory and mode-coupling theory. A mathematical expression is
obtained for the complete single MMF imaging system, which is further validated
by image-transmission simulations. Our model is believed to be the first
theoretical model to describe the complete MMF imaging system based on the
transmission of individual modes. Therefore, this model is robust and capable
of analyzing MMF image transmission under specific mode-coupling conditions. We
use our model to study bending-induced image blur in single-MMF image
transmission, and the result has found a good agreement with that of existing
experimental studies. These should provide important insights into future MMF
imaging system developments.
