A full-duplex radio-over-fiber (RoF) system with optical millimeter-wave generation utilizing optical phase modulator was designed and experimentally demonstrated. Carrier suppression double sideband optical signal with 40 GHz repetitive frequency is generated by using an optical phase modulator along with optical filtering technique. An optical interleaver was employed to separate the two first-order sideband carriers, one of the carriers was used to carry 2.5 Gbit/s downstream data, while the other was sent to base station for reuse for modulating upstream data. It was experimentally demonstrated that the 2.5 Gbit/s data for bidirectional transmission were transmitted over 40 km standard single mode fiber (SMF-28) with less than 0.5 dBm power penalty. By using optical phase modulator along with optical interleaver to generate optical mm-wave, and adopting the wavelength reuse technique, the proposed RoF system becomes simple and cost-effective.