Low Complexity Digital Predistortion for Multiband Radio Over Fiber Systems

Nonlinear distortion is one of the limiting factors in radio over fiber (RoF) transmission systems. To suppress the nonlinear distortion, digital predistortion (DPD) has been investigated considerably. However, DPD for multiband signals becomes very complex. In this work, a new low-complexity multiband DPD is proposed, in which in-band and out-of-band distortions are separated and the out-of-band distortion is evaluated by sum and differences of all input signals instead of all individual input signals; thus, complexity is reduced. A five-band 20-MHz 64-quadrature amplitude modulation (QAM) orthogonal frequency division multiplexing (OFDM) signals over an 8-km RoF link with the DPD is tested. The average improvement of error vector magnitude (EVM) is 8.1 dB. The model is further validated by simulation.