The insensitivity to phase noise of envelope detection in mobile terminals is theoretically proven and experimentally confirmed. Successful generation and transmission of 640-Mbps OFDM signals at 60 GHz was achieved by heterodyning phase-uncorrelated laser signals with a combined linewidth closed to 1 MHz. Experimental results show the significant effect of the relative intensity noise but a minimal impact of the fiber chromatic dispersion, making this technique a cost-efficient candidate for long-reach RoF systems.