噪声对消射频光子链路的噪声系数研究

Research on noise figure of RF photonic link with noise cancellation

噪声系数是宽带射频光子链路的重要参数,影响 射频信号传输和处理系统的信噪比。 提出了一种噪声对消射频光子链路,采用平衡光探测器对直流光和调制光转换的光电流相减 处理,得到链路的噪声系数改善。从光信号调制、探测及噪声功率变化特性出发,建立了噪 声对消射频光子链路的理论模型,并通过理论分析研究了噪声系数与激光功率、相对强度噪 声、光调制器损耗、光耦合器分光比等参数的关系。构建了噪声对消射频光子链路实验,对 频率6~18 GHz的噪声系数进行对比研究。实验研究结果表明,在相同 条件下,噪声 对消射频光子链路的噪声系数减小2~4 dB。理论和实验结果充分证 明提出的方法正确性。

Noise figure is the important parameter of wideband RF photonic link,which can affect signal to noise ratio of RF transmission and processing system.However,noise figure of RF photonic link is generally deteriorated by related optical noise.In this paper,a novel RF photonic link with noise cancellation i s proposed.In this kind of RF photonic link,noise figure can be improved by de tecting direct current light signal and modulated light signal with the same opt ical power at balanced photodetector.According to the variation feature of sign al and noise,a theoretical model about noise figure of RF photonic link with no ise cancellation is built,and the expressions and characteristics about noise f igure are investigated.The relationship between noise figure and laser power,r elative intensity noise,optical loss of modulator and coupling ratio of optical coupler is demonstrated in theory.In the experiment of RF photonic link with n oise cancellation,noise figure with the frequency of 6~18GHz is studied in comp arison.It is shown that noise figure of RF photonic link with noise cancellatio n can be improved 2~4dB under the same condition.The theoretical analysis and e xperimental results can prove the validity of noise subtracting method in RF pho tonic link.RF photonic link with noise cancellation can be applied in practice.