Impairment Mitigation for a 60 GHz OFDM Radio-Over-Fiber System Through an Adaptive Modulation Technique

We investigate several existing impairments in an orthogonal frequency-division-multiplexed radio-over-fiber (OFDM-ROF) system delivering a 60 GHz optical millimeter wave with double optical sidebands and a suppressed central carrier. It is found through theoretical analysis and numerical simulation that intersubcarrier interference and frequency-selective fading are the dominant factors degrading the OFDM-ROF system performance. With that in mind, we propose and experimentally demonstrate what we believe to be a novel scheme to mitigate system impairments in an OFDM-ROF link by using the adaptive modulation technique in which different subcarriers may have different modulation formats according to their signal-to-noise ratio over the ROF channel.