Abstract: In order to increase the transmission distance for optical millimeter wave over an optical fiber,a novel scheme for optical millimeter wave generation with optical carrier suppression(OCS) modulation by external modulator in a radio over fiber(ROF) system was proposed.At the central station,a CW wave was intensity modulated by the RF signal to generate OCS signal.After the pure optical carrier was filtered,an optical interleaver was employed to separate the spectrum of the upper sideband and the lower sideband of the generated OCS signal.After the lower sideband signal was modulated with a baseband data at 2.5Gbit/s,it was recombined with the unmodulated signal to generate optical mm-wave,and then transmitted to the base station over a single mode fiber(SMF).In the base station,the electrical mm-wave signal was generated by optical electrical(O/E) conversion.The dispersion performance of the generated mm-wave was theoretically analyzed.The optical millimeter wave could be transmitted 40km over a single mode fiber in the experiment.The simulation and experiment results show that it can immune the fading effect and increase the transmission distance for optical millimeter wave over fibers with this method.