  Multimode fiber (MMF) has been proven to have good potential in imaging and
optical communication because of its advantages of small diameter and large
mode numbers. However, due to the mode coupling and modal dispersion, it is
very sensitive to environmental changes. Minor changes in the fiber shape can
lead to difficulties in information reconstruction. Here, white LED and
cascaded Unet are used to achieve MMF imaging to eliminate the effect of fiber
perturbations. The output speckle patterns in three different color channels of
the CCD camera produced by transferring images through the MMF are concatenated
and inputted into the cascaded Unet using channel stitching technology to
improve the reconstruction effects. The average Pearson correlation coefficient
(PCC) of the reconstructed images from the Fashion-MINIST dataset is 0.83. In
order to check the flexibility of such a system, perturbation tests on the
image reconstruction capability by changing the fiber shapes are conducted. The
experimental results show that the MMF imaging system has good robustness
properties, i. e. the average PCC remains 0.83 even after completely changing
the shape of the MMF. This research potentially provides a flexible approach
for the practical application of MMF imaging.
