Terahertz Signal Transparent Relay and Switching Using Photonic Technology

Terahertz-wave (THz) is considered a potential candidate for extreme communications in 6G and beyond networks owing to its large bandwidth. Nevertheless, extremely high free-space loss and weak penetration remain as bottlenecks, which makes it difficult to transmit THz signals from outdoor to indoor and in areas having barriers, walls, and obstacles. In this study, we propose a dual-hop access network in the THz band using photonics-enabled signal transparent relay and routing. In the system, THz signals are received and directly converted to optical signals using THz-to-optical converters. After transmission over fiber links, the signals are converted back to THz signals without using any waveform and frequency conversions. As the proof-of-concept demonstration, the transparent relay and switching of THz signals is demonstrated using a low-loss optical modulator and ultra-fast tunable laser. A 32-Gb/s orthogonal frequency-division multiplexing signal was successfully transmitted over a switchable fiber–THz–fiber–THz system in the 285-GHz band. The possibility of switching the THz signals in ultrashort time of 10 μs was experimentally confirmed. The proposed system paves the way for the deployment of THz communications in 6G and beyond networks.