Full duplex radio over fiber system with frequency quadrupled millimeter-wave signal generation based on polarization multiplexing

A full duplex radio over fiber system with frequency quadrupled millimeter-wave signal generation based on polarization multiplexing using a single-drive intensity modulator is proposed and experimentally demonstrated. At the central station, downstream signal modulated on the single-drive intensity modulator is polarization multiplexed with pure optical carrier by a polarization beam combiner (PBC) before transmitted over the single mode fiber to the base station. The single-drive intensity modulator is biased at the maximum transmission point to generate optical carrier and two second-order sidebands. At the base station, by simply adjusting the difference angle between the principle axis of polarizer and one principle axis of PBC to 135°, a frequency quadrupled millimeter-wave signal is generated. In addition, when the difference angle between the principle axis of polarizer and one principle axis of PBC is adjusted to 90°, the original pure optical carrier is recovered, which is wavelength reused to provide light source for the uplink to deliver upstream signal. A proof-of-concept experiment is performed. Pure optical carrier and 40 GHz millimeter-wave signal with 20 dB optical harmonic suppression ratio are obtained. The power penalties of the bidirectional links are less than 0.3 dB after transmitted over 10.5 km single mode fiber. The measured power fluctuation of the generated millimeter-wave signal is less than 1 dB in one hour, showing the proposed scheme is relatively stable for long-distance transmission system.