Distortion Mitigation in Multiband OFDM RoF Transmission Employing Blind Post Equalizer

We propose and experimentally demonstrate a blind adaptive equalizer for a multiband (MB) orthogonal frequency-division multiplexing (OFDM) radio-over-fiber (RoF) system. The proposed equalizer adaptively decreases nonlinear and linear distortion, which might lead to serious signal degradation in MB OFDM transmission, without the use of a training signal. Instead of a training signal, error vector magnitude (EVM) and the power difference between the signal and the third-order intermodulation distortion components were observed in the equalizer. Therefore, the performance enhancement of MB OFDM transmission was experimentally verified in terms of EVM from 5.52% to 2.75% by mitigation of distortion. Consequently, the dynamic range of radio frequency input power was improved when the proposed equalizer was employed in an MB OFDM RoF system without increasing system overhead.