概率整形相位共轭孪生波OFDM WDM系统IQ不平衡研究

Study of IQ imbalance in probabilistic shaping phase conjugate twin waves OFDM WDM system

为探究IQ不平衡产生机理,结合偏振复用(PDM)、16进制正交幅度调制(QAM)、相位共轭孪生波(PCTW)、正交频分复用(OFDM)、波分复用(WDM)等技术,采用Opti System软件搭建了PCTW-OFDM-WDM系统,分析了概率整形、串扰、统计相关噪声引起IQ不平衡的机理。理论分析和仿真结果表明:IQ不平衡是由多种因素造成的,只有过大的IQ不平衡才会对系统性能产生较为明显的影响;几何整形方案对系统IQ不平衡和性能改善的作用有限;在时隙和子载波PCTW模式下,适当地改变共轭分量的分布位置可有效改善IQ不平衡,并获得比相邻结构更好的传输性能表现。

In order to explore the mechanism of IQ imbalance, combining polarization multiplexing(PDM), hexadecimal orthogonal amplitude modulation(QAM), phase conjugate twin waves(PCTW), orthogonal frequency division multiplexing(OFDM),wave division multiplexing(WDM) and other technologies, this paper uses OptiSystem software to build PCTW-OFDM-WDM system. The mechanism of IQ imbalance caused by probabilistic shaping, crosstalk and statistical correlation noise is analyzed.The theoretical analysis and simulation results show that IQ imbalance is caused by many factors, and only a large IQ imbalance will have a significant impact on the system performance. Geometric shaping scheme has limited effect on IQ imbalance and performance improvement. In the time slot and subcarrier PCTW mode, appropriately changing the location of the distribution of the conjugate components can effectively improve the IQ imbalance and obtain better transmission performance than adjacent structures.