The application of Radio-Over-Fiber (ROF) links are widely used in wireless communications. However, due to the nonlinear characteristics of the link distortion will be introduced as the output of the link. As a result, unwanted frequencies and signals end up being delivered by an antenna. In the thesis, a technique of adaptive digital predistortion is presented. This complex gain predistortion technique requires that no detailed knowledge of the link characteristics and supports tracking of the modifications and drifts in the link characteristic. A prototype of this predistortion system is designed and implemented on a Field Programmable Gate Array (FPGA). Experiment results show that amplitude and phase nonlinearity of the ROF link are compensated with the system. The experiments demonstrated that this system show promising results and that good compensation of distortion is achieved.