Single‐Shot Simultaneous Recovery of Phase and Degree of Polarization in Multimode Fibers via Physics‐Constrained Global Attention

ABSTRACT

Concurrently recovering the vectorial optical field, including the spatial phase and degree of polarization at the distal end of a multimode fiber using interferometer‐free measurements remains an open challenge. Existing computational approaches typically retrieve phase or polarization separately, as jointly decoding both quantities from a single scalar measurement constitutes a highly ill‐posed. Here, we demonstrate single‐shot simultaneous reconstruction of phase and degree of polarization from a single non‐interferometric speckle intensity frame. A dual‐path spatial‐multiplexing system provides ground‐truth intensity, phase, and degree of polarization for a global transposed‐attention neural network matched to multimode‐fiber coupling. Moreover, we incorporate two physics‐based constraints into the network: a unit‐circle manifold prior that suppresses modulus divergence, and a cosine‐similarity alignment loss that prevents phase inversion, both guiding the network toward physically consistent solutions. On the test set, PI‐Restormer achieved phase PCC/SSIM values of 0.6072/0.7107 and cRMSE of 0.5115 rad, together with degree‐of‐polarization PCC/SSIM of 0.8987/0.6559. Among the four tested backbones, PI‐Restormer achieved the best phase reconstruction. A separate mechanically perturbed fiber experiment demonstrated the robustness of the proposed method. By replacing interferometric and polarizer‐analyzer hardware with an ordinary camera, this approach opens the door to compact fiber imaging and multidimensional sensing.