Dual‐Metasurface‐Integrated Fiber Array for Bidirectional Cylindrical‐Vector‐Beam Multiplexed Communication Using Off‐Axis Spatial Manipulation

Abstract

ABSTRACT Free‐space optical (FSO) communication is expected to support 6G networks, and cylindrical vector beam (CVB) multiplexing offers a promising space‐division multiplexing (SDM) dimension for high‐capacity FSO links. However, conventional CVB generators offer limited bidirectional, multichannel control of off‐axis polarization/topology, and typically require bulky cascaded optics with repeated multi‐element alignment. Here, a compact, high‐capacity bidirectional CVB‐SDM FSO architecture is presented by integrating a fiber array with a dual‐layer metasurface (MS) on its facet. The first MS employs an optimized quadratic‐phase profile obtained through damped‐least‐squares optimization for multichannel off‐axis collimation, whereas the second combines a Dammann vortex grating with Pancharatnam–Berry phase engineering to realize the polarization/topology transformation required for CVB multiplexing and demultiplexing. Experimentally, three CVB channels were operated with two separately tested dual‐wavelength pairs, 1530/1550 nm and 1550/1570 nm. For each wavelength pair, an aggregate data rate of 75 Gbps was achieved, corresponding to two wavelengths × three CVB channels × 12.5 Gbps, at a received power of −17 dBm, with an average bit‐error rate of 8.79 × 10 − 10 per channel over 2.5–12.5 Gbps. This integrated platform reduces component count, enables compact plug‐and‐play deployment, and provides a scalable interface for next‐generation multidimensional high‐throughput FSO communication.