Hybrid THz/FSO Transmission System with a Shared Photonic Transmitter Enabled by PMMA-Based Beam Combining

Hybrid terahertz (THz)/free-space optical (FSO) systems offer a promising paradigm for high-capacity, all-weather wireless communication, yet their deployment is often hindered by the bulky size and high complexity of discrete transceivers. This paper experimentally demonstrates a low-complexity hybrid THz/FSO transmission architecture featuring a unified photonic transmitter. By leveraging a polymethyl methacrylate (PMMA) plate serving as a dichroic beam combiner—which reflects the 1550 nm optical signal while transmitting the 300 GHz THz signal—we realize simultaneous signal propagation over a shared aperture and link. Photonics-aided techniques are employed to generate both carriers, ensuring system integration and coherence. The experimental results verify that both the THz and FSO links independently support 30-GBaud quadrature phase-shift keying (QPSK) transmission over a 10-m wireless distance, achieving a net data rate of 60 Gbps per link while satisfying the 7% hard-decision forward error correction (HD-FEC) threshold of 3.8 × 10−3. This work validates the feasibility of shared-transmitter designs and provides a compact, cost-effective solution for future high-speed fronthaul/backhaul networks.