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正交频分复用OFDM(Orthogonal Frequency Division Multiplexing)与光载无线电ROF(Radio Over Fiber)技术结合为实现低成本、高速数据传输的无线网络提供了可能。但RoF链路的非线性降低了系统性能。文中在分析Mach-Zehnder调制器的静态模型基础上,提出用Volterra级数与冲击响应分析模型相结合模型化RoF非线性系统。在此模型基础上分析Mach-Zehnder调制器以及射频放大器非线性对OFDM信号的影响。仿真分析显示非线性会使OFDM信号频谱展宽,降低信号幅度,并且随着光调制指数的增加误差矢量,带外干扰增加。为OFDM-RoF系统的线性化处理以及系统光调制器调制指数的选择提供了理论依据。
The combination of Orthogonal Frequency Division Multiplexing (OFDM) and Radio Over Fiber (ROF) provides the possibility of a wireless network that enables low-cost, high-speed data transmission. However, the nonlinearity of RoF links reduces system performance. Based on the analysis of the static model of the Mach-Zehnder modulator, a nonlinear RoF system based on Volterra series and impulse response analysis model is proposed. Based on this model, the influence of the Mach-Zehnder modulator and the nonlinearity of the RF amplifier on the OFDM signal is analyzed. Simulation results show that nonlinearity can broaden the spectrum of OFDM signal, reduce the signal amplitude, and increase the error vector and out-band interference with the increase of optical modulation index. It provides a theoretical basis for the linearization processing of OFDM-RoF system and the selection of the modulation index of the system optical modulator.