微波光链路(MPL)是利用光纤传输微波信号,与传统的射频链路相比具有带宽大、损耗小、质量轻、抗电磁干扰等优势,但也存在噪声系数较大的问题,从而影响链路的动态范围。建立了直接调制的微波光链路模型,在不考虑频响的情况下推导出链路固有增益和噪声系数的表达式,研究了激光器的转换效率、光纤的损耗和相对强度噪声(RIN)对链路噪声系数的影响。还建立了链路频响的模型,推导出固有增益与频率关系的表达式,分析仿真了频率对链路固有增益和噪声系数的影响,并与实验结果进行了比较。

Compared with the conventional microwave links,microwave photonic links(MPL) can provide much wider bandwidth,lower loss,reduced weight and susceptibility to electromagnetic interference in the propagation of microwave signal by optical fiber. However MPL is generally limited by high noise figure,which affects the dynamic range of system. A model about directly modulated MPL is built,and the expression about noise figure of ignoring frequency dependence is deduced. The relationship between noise figure and modulation efficiency,the loss of the fiber,as well as RIN is simulated. The frequency response model of the link is also built,and then the effects of frequency on the intrinsic gain and noise figure of MPL are investigated and compared with the result of experiments.