Radio over 50 km Fiber and Joint 80 m FSO/Wireless Links Using Photonic Frequency Doubling for 5G

We present the experimental demonstration of photonic doubling to achieve 25 GHz millimeter wave signal generation, following the 5th generation network frequency band recommendations. A hybrid optical network combining up to 50 km long radio over fiber and 40 m long radio over free space optics systems plus 40 m long radio frequency (RF) 25 GHz wireless channel is demonstrated. The proposed system employs double sideband suppressed carrier modulation with 27 dB optical carrier suppression ratio and RF carrier phase noise below - 107 dBc/Hz with 10 kHz offset. The proposed system is optimized in terms of RF input power and the system quality is tested in terms of error vector magnitude for different modulation formats and variable fiber section lengths. Furthermore, the effect of optical atmospheric turbulence on longer FSO spans is investigated.