M.Sc Thesis

M.Sc StudentFertman Alexander
SubjectImage Transmission through a Multimode Optical Fiber Using
Numerical Phase Retrieval
DepartmentDepartment of Biomedical Engineering
Supervisor ASSOCIATE PROF. Dvir Yelin
Full Thesis textFull thesis text - English Version


In this work we present a theoretical analysis of a method for transmitting an image through a single multimode optical fiber. The key challenge in using multimode fibers for 2D image transmissions is modal dispersion. It is unpredictable for all practical cases, changes in time and severely corrupts the input image after just a few millimeters of propagation in a fiber. We show that it is possible to evaluate the entire instantaneous transfer function of a multimode fiber by transmitting a known field (reference) immediately before or after the desired 2D image (object), and use this information to recover the latter by numerically descrambling the output image in fiber mode space. This method may be realized using simple optical components, however, it requires knowledge of the full output field (both amplitude and phase). We compute the field emanating from the fiber by applying a modified Gerchberg-Saxton algorithm for phase retrieval, which results in high quality image reconstruction at low-to-moderate noise levels. The method, however, poses a number of challenges in its practical implementation, including unpredicted imperfections and design tolerances in the optical fiber, unaccountable modal dispersion due to polarization cross-talk in mechanically stressed fibers and practical challenges in field measurement.