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提出了一种利用分布反馈DFB(Distributed Feedback laser)激光器的非线性对射频光传输系统动态范围进行优化的方案。实验研究了半导体分布反馈激光器的非线性,基于实验结果分析了DFB激光器的偏置电流与线性性能的关系。在此基础上建立了对马赫曾德外调制(Mach-Zehnder modulator,MZM)射频光传输系统线性优化方案。实验结果表明,该实验系统有效抑制了系统三阶交调量,系统的动态范围得到改善,当输入射频信号中心频率4 GHz,双音号间隔10 k Hz时,三阶交调失真抑制23.1 d B,无杂散动态范围提高8.68 d B。
A scheme of using nonlinear feedback of distributed feedback laser (DFB) to optimize the dynamic range of RF optical transmission system is proposed. The nonlinearity of semiconductor distributed feedback laser was experimentally studied. Based on the experimental results, the relationship between the bias current and linearity of DFB laser was analyzed. On this basis, a linear optimization scheme of the Mach-Zehnder modulator (MZM) RF optical transmission system is established. The experimental results show that the experimental system effectively suppresses the third-order intermodulation of the system and the dynamic range of the system is improved. The third-order intermodulation distortion is suppressed by 23.1 d when the center frequency of the radio frequency signal is 4 GHz and the dual-tone spacing is 10 k Hz. B, spurious-free dynamic range increased 8.68 d B.