Multi-level ASK demonstrations in millimeter-wave radio-over-fiber system using free-running lasers and RF self-homodyning

Schemes for spectrally-efficient and simplified millimeter-wave radio-over-fiber (RoF) system have been proposed. Two free-running and uncorrelated optical carriers are heterodyned for optical mm-wave signal generation at the central station (CS). The generated phase noise at mm-wave carrier frequency is overcome by using RF self-homodyning at the receiver. Multi-level amplitude-shift-keying (M-ASK) modulation using 4-ASK non-return-to-zero (NRZ) format with a total data rate of 5 Gbps have been applied and experimentally demonstrated in two different signal generation schemes for downlink. Apart from relaxing the requirements of high-speed electro-optic and RF devices both at the CS and base station (BS), the proposed system is transparent to any operating mm-wave frequencies and provides a spectrally-efficient and simplified solution.