© 2014 IEEE. We propose and demonstrate a 25-Gb/s 16-quadrature amplitude modulation orthogonal frequency division multiplexing 60-GHz radio over fiber transmission system based on a gain-switched optical comb source. The impact of the phase noise caused by the optical phase decorrelation due to the chromatic dispersion is theoretically studied and experimentally investigated by employing a high linewidth comb source and transmitting over a 50-km standard single-mode fiber reel. A time delay precompensation is deployed based on the study of phase noise in order to reduce the phase noise impact, and thereby improve system performance.