针对未编码离散多音频调制(DMT)的阶跃折射率塑料光纤(SI-POF)通信系统传输容量的计算，采用均匀功率谱密度(PSD)注入的方法，对SI-POF 强度调制直接检测(IM/DD)的通信传输进行数学建模。借助一阶低通和高斯低通信道模型，推导出基于信噪比(SNR)间隔的信道容量和最佳使用带宽的数学计算模型。在不同使用带宽下对系统容量进行了理论分析与数值计算，并分别取不同长度的SI-POF 进行实物传输测试。理论计算和传输实验表明了该计算模型的准确性，且信道容量与等效信噪比呈正向分布，与传输距离呈反向变化；使用优化的传输带宽可以减小传输速率的损失。该模型可有效用于SI-POF 通信系统的容量计算和最优带宽预测。

Considering the calculation of channel capacity of the step- index polymer optical fiber (SI- POF) communication system within the uncoded discrete multitone modulation (DMT), the intensity modulated direct detected (IM/DD) transmission scheme is mathematically modeled, and a novel uniform power loading technique is used to evaluate and calculate the maximum achievable date rate. With the help of Gaussian and first-order low pass filter channel model, the theoretical expressions for the optimal bandwidth and realistic capacity of SI-POF system are derived based on signal to noise ratio (SNR) gap. The numerical calculations with different equivalent SNRs and occupied bandwidths are compared and the real experimental transmissions with several fiber lengths are also implemented. The results demonstrate that the channel capacity is positively distributed to the equivalent SNR, yet inverse with the fiber lengths. Adopting the optimum bandwidth can effectively reduce the transmission rate loss. By the analysis, the accurate prediction of capacity is beneficial to the POF system designing.