Multimode fibers (MMFs) hold great promise for a variety of imaging applications. However, controlling the complex propagation of light through thousands of modes in MMFs remains a challenging task. To enable precise wavefront control, the MMF transmission matrix (TM) must be accurately measured. In this paper, we compare in-line and off-axis holography as phase retrieval techniques for TM measurement within a single optical setup. The quality of wavefront shaping is analyzed for different target shapes, including single-mode and complex free-form projections. Our findings reveal a trade-off in wavefront shaping: while in-line holography achieves superior focus quality for single-mode targets, off-axis holography excels in projecting complex-shaped targets. These experimental findings provide a basis for choosing and optimizing holographic techniques in MMF-based imaging setups.
Copyright: © 2026 Ivanina et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.