Abstract

The aim of this work is the utilization of individual multimode fibers for the purposes of microendoscopy. In the present contribution we discuss the question of image aberration induced by transmission along the fiber proposing a restoration algorithm. Under LP conditions, and for not too large core diameters, the main cause of aberration is intermodal dispersion, but in this work we demonstrate that it may be computed and corrected. We implemented a restoration algorithm based on the separation and equalization of the contribution of each mode, for both step-index and graded- index fibers. Simulations show that fibers with a diameter of few tens of microns can transmit even quite detailed images, and the proposed algorithm is effective for both the above types of fibers, for different fiber lengths and for a variety of images. Experimental tests were performed by transmitting a Gaussian beam through a graded index silica fiber (diameter 62.5 μm, NA=0.275). After applying the proposed post-processing to the aberrated image exiting from the fiber, we obtained an error of 0.25 pm on the FWHM of the original Gaussian beam. In conclusion, it appears possible to “capture” an external image and transmit the same through the fiber towards an observer at the other fiber end, after appropriate phase correction.

© 2007 SPIE