提出了一种基于低密度奇偶校验码（LDPC）的概率整形（PS）方案，以优化正交频分复用（OFDM）信号在光载无线（RoF）通信系统中的传输性能。首先，理论分析了PS技术和PS-OFDM信号的生成原理，该方案的冗余度为6.7%，相比传统的OFDM信号平均功率降低了约20%。接着，在理论研究的基础上建立了仿真验证系统，与传统OFDM-RoF系统相比，该系统可明显降低OFDM信号的平均发射功率，在相同平均发射功率下改善系统的峰值平均功率比（PAPR）。最后，对该系统在不同光纤传输距离下的误码率分析结果表明，在基带数据速率为2.5 Gbps，射频载波频率为25 GHz的情况下，基于LDPC的PS-OFDM-RoF系统可以有效改善接收机的灵敏度，并增加系统的可靠传输距离。

In this study, we propose an orthogonal frequency division multiplexing radio-over-fiber (OFDM-RoF) system based on low density parity check code (LDPC) coded with probabilistic shaping (PS) for optimizing the transmission performance of the OFDM signal. We theoretically analyze the PS technology and the generation and demodulation principle of the PS-OFDM signal. The average power of the modulated OFDM signals for the same transmission power decreased by approximately 20% after PS with a 6.7% extra overhead. Compared with a normal OFDM-RoF system, the proposed PS-OFDM-RoF system can reduce the transmitting power of OFDM signals, and it has a better peak-to-average power ratio (PAPR) performance. Furthermore, a 25 GHz verification RoF system with a data rate of 2.5 Gbps is established for analyzing the transmission characteristics of the PS-OFDM signals. The measured bit error rate curves at different fiber lengths show that a PS-OFDM-RoF system based on LDPC can effectively improve the sensitivity of the receiver and increase the reliable transmission distance of the system.