在探测器光电转换效率的理论分析和实际测试结果基础上，建立了其功率电流(P-I)特性的非线性模型。基于该模型分析了探测器工作于线性区和饱和区的光电转换能力，将实际测试结果和理论分析结合，研究了探测器响应度饱和情况下可见光通信系统的幅频响应的变化。实验结果表明在可见光通信(VLC)系统的设计中，荧光粉的余辉虽然不会被高速调制，但是它会降低光电探测器的幅频响应度，由于光功率过大导致的探测器响应度饱和会影响系统的幅频响应幅值和系统带宽。

A nonlinearity model of the detector′s power-current (P-I) characteristics is established based on the theories and experiments in respect to photo-electric conversion efficiency. The model is used to analyze the detector′s photo-electric convertion ability in both linear and nonlinear cases. With the theories and experiments, the frequency response of the visible light communication (VLC) system when photodiode becomes saturated is studied. It proves that although the afterglow of fluorescent powder cannot be modulated in high speed, it can decrease the frequency response of the detector. The detector′s saturation due to the high optical power has an effect on the frequency response and the bandwidth in VLC system.