A Scalable 26 GHz RoF Relay System Using Optoelectronic Extender

This letter presents data transmission over a 26 GHz millimeter-wave (mmW) radio signal and its coverage extension in an indoor environment using the radio-over-fiber (RoF) technology. The proposed system consists of two RoF seamless wireless links to emulate a mobile fronthaul using a transparent RoF relay link to overcome higher attenuation of the mmW signal. The system is experimentally evaluated for up to 64-quadrature amplitude modulation (QAM), showing the possibility of signal transmission over up to 20 km of optical fiber in the first Section transmission scheme without the usage of an optical amplifier. For the system with 20 km and 30 m long RoF links as well as 4 m and 1 m long relays with no optical amplification, the minimal experimentally measured error vector magnitude is as low as 5% for 64-QAM. Further, a self-developed integrable optoelectronic extender is used for the relay RoF system to simplify the antenna site and keep its footprint small. Moreover, the proposed setup is extended using an optical amplifier toward a scalable scheme with up to 75 km of optical fiber and 5 m long free space optical link.