Tunable THz Signal Generation and Radio-Over-Fiber Link Based on an Optoelectronic Oscillator-Driven Optical Frequency Comb

Abstract

We propose and demonstrate experimentally a photonic THz signal generation technique based on a tunable optoelectronic oscillator (OEO), and its application in a radio over fiber (RoF) link. The OEO's frequency is tuned by varying the bandwidth of a tunable optical bandpass filter (TOBF) that is cascaded with a phase modulator (PM). The resulting tunable microwave photonic filter is used to generate OEO oscillations from 6.58 GHz up to 18.36 GHz (with a phase noise of ≤−103 dBc/Hz at 10 kHz offset from the carrier frequency). The OEO is subsequently used to drive an optical comb, generating 22 comb lines with a frequency spacing of 17.33 GHz covering a bandwidth of 360 GHz within a 20 dB envelope. By selecting two optical comb lines with a wavelength selective switch (WSS) and beating them in a uni-traveling carrier photodiode (UTC-PD), THz signals are generated at 101.5 GHz and 242.6 GHz with phase noise of −90 dBc/Hz and −78 dBc/Hz, respectively at 10 kHz offset from carrier frequency. Tunable mm-wave and THz signals can be generated either by changing the OEO oscillation frequency or the selected comb lines. Using the OEO driven OFCG, we implemented a RoF link at 242.6 GHz with a data rate of 24 Gbps over a wireless distance of 30 cm and with a bit error rate (BER) below the hard decision forward error correction (FEC) limit of 3.8 × 10−3. This method allows the creation of an all-photonic frequency reconfigurable THz signal generator and RoF system.