基于级联光纤环微波光子滤波器的微波倍频技术

Microwave frequency multiplication based on cascaded fiber ring microwave photonic filters

为了得到高倍频的微波信号,实现获得了一种基于外调制技术与级联光纤环微波光子滤波器(FRMPF,fiber ring microwave photonic filters)的新型倍频微波信号光学产生技术。利用外调制的方法,采用大功率信号驱动马赫曾德尔调制器(MZM)得到了高阶谐波信号,再利用级联的FRMPF进行选频。理论计算与实验测试了FRMPF的滤波特性。通过调节每个FRMPF的环长,利用第1个FRMPF将基频信号与三阶谐波滤除,再通过第2个FRMPF将二阶谐波滤除,最终得到四倍频信号。研究结果表明,利用频率为2.018 3GHz的信号驱动MZM,得到了频率为8.073 2GHz的四倍频信号,信噪比(SNR)大于13dB。

In this paper,a novel approach of microwave frequency multiplicatio n by using a Mach-Zehnder modulator（MZM） and cascaded fiber ring microwave ph otonic filters （FRMPFs） was proposed and experimentally demonstrated.High order harmonics are generated thro ugh external modulation with large microwave signal,and cascaded FRMPFs can be utili zed to filter out the low frequency harmonics.The performance of the FRMPF is theoretically analyzed ,optimized and experimentally measured.By carefully adjusting the length of each FRMPF through tuning the optical delay line and optimizing the coupling ratio of the optical couplers in the FRMPFs,the desirable harmonic can be selected.In our experiment,two cascaded FRMPFs are used,and by u sing the first one,the first and third harmonics are filtered out while the second harmonic is filtered out by the second FRMPF,with only the fourth harmonic left after beatin g o n the photodiode with proper bandwidth.The experimental results show that by modulating a driving sig nal with frequency of 2.0183GHz,a signal with frequency of 8.0732GHz,which is four times of the driving frequency,is generated and the signal to noise ratio （SNR） is more than 13dB.