Reconfigurable 2D Optical Beamformer Based on a Dispersion-Diversity Heterogeneous Multicore Fiber

We propose and experimentally demonstrate a reconfigurable two-dimensional (2D) photonic beamformer architecture based on a dispersion-diversity heterogeneous multicore fiber (MCF) and fiber Bragg grating (FBG) arrays. The system employs two independent true-time-delay-line (TTDL) stages that enable 2D beamforming using a single tunable laser source. Continuous and discrete control of the azimuth and elevation angles, respectively, is achieved by combining wavelength-dependent beam-pointing angle periodicity with the dispersion diversity of the heterogeneous MCF. The distributed beamformer concept is validated for a 5×5 equivalent phased antenna array using 5-km heterogeneous MCF and an FBG array composed of seven gratings inscribed in each of five single-mode fibers. Each FBG was inscribed using a femtosecond laser at a specific longitudinal location and centered at a distinct wavelength within the 1530–1573 nm range. As a proof of concept, the system demonstrates continuous azimuthal steering over 90° and seven discrete elevation angles from −45° to +45°. Measurements of differential group delay and phase difference across all outputs show an average time-delay error below 0.5 ps with a maximum standard deviation of 1.03 ps, corresponding to a beam-pointing error under 2°. The retrieved array-factor patterns closely match theoretical predictions, confirming precise control in both azimuth and elevation. Overall, this work presents a compact, energy-efficient, and reconfigurable photonic architecture for 2D beamforming, offering a scalable, fiber-distributed solution for next-generation, beyond-5G, and 6G communication systems.