Experimental demonstration of a photonics-assisted dual-hop radio-over-fiber system for routing and relaying W-band MMW signals

Millimeter-wave (30-300 GHz) communication is considered a key enabler for future indoor and access networks due to its ultra-wide bandwidth and capability of supporting high data rates. However, millimeter-wave signals suffer from severe free-space path loss and are sensitive to obstructions; their excessive penetration loss further limits reliable indoor and urban coverage. To overcome these challenges, we experimentally demonstrate a photonics-assisted dual-hop radio-over-fiber (ROF) system for routing and relaying W-band millimeter-wave signals. The proposed dual-hop communication system utilizes photonic technology to deliver millimeter-wave signals from the central station to end users. Without requiring electrical frequency conversion, the system reduces signal distortion and preserves transmission quality. Using this scheme, we successfully achieved 80 Gbit/s 16-QAM transmission over a 21-km fiber link and two 1-m wireless hops at 90 GHz when the routing optical wavelength was 1550 nm. Moreover, by sweeping the routing wavelength from 1545 to 1554 nm, the system sustained a maximum data rate of 80 Gbit/s. Unlike conventional millimeter-wave systems, the proposed dual-hop architecture supports signal relay without strict line-of-sight requirements, which significantly improves transmission flexibility and coverage.