The high-speed train in Japan connects megalopolises through many tunnels or underground routes. To provide seamless internet connectivity to the hundreds of passengers on the train, a new backhaul communication system is proposed in a millimeter-wave band by Radio over Fiber. We have shown that a vector-modulated signal can be generated by multiplying the radio frequency in the optical domain to avoid effects of chromatic dispersion in an optical fiber. In this paper, we show characteristics of long distance transmission by Radio over Fiber. Also, we present our concept and report on the relationship between the symbol rate and the modulation accuracy of the 96 GHz band signal generated by frequency doubling using RoF.