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

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.