微波光子滤波器的平坦特性分析

Flat analyzing of the microwave photonic filter

随着微波光子学的发展,微波光子滤波器的应用和研究逐步成为研究热点,在深入研究光纤光栅、马赫曾德尔调制器以及掺铒光纤的基础上,提出了一种平坦微波光子滤波器的结构,通过理论计算和仿真,在光纤耦合器耦合系数为0.5、光纤光栅反射率为0.33、掺铒光纤增益为10,以及光纤耦合器耦合系数为0.4、光纤光栅反射率为0.5、掺铒光纤增益为2时,分别实现了平坦带通和平坦带阻响应,对滤波器的平坦条件进行了深入研究,得到了只有当两部分滤波器的延时差相等才能实现平坦的必要条件,并依据此分析了影响滤波器周期的因素,提出了利用曝光光敏光纤增加光纤折射率从而增加滤波器延时的方案,从而补偿了长度控制上的精确度对该结构的限制。

With the development of the microwave photonics,the research and application of the microwave photonic filter have gradually become a hot spot.Based on the study of fiber Bragg grating（FBG）,Mach-Zehnder modulator and erbium-doped fiber（EDF）,a kind of flat microwave photonic filter was put forward.When the coupler factor was 0.5,the reflectivity of the FBG was 0.33,the gain of the EDF was 10,a flat band pass response was obtained.And when the coupler factor was 0.4,the reflectivity of the FBG was 0.5,the gain of the EDF was 2,a flat band stop response was got.Through deep study of the flat condition,flat could be gained only when the delay difference of the two filters was equal.Based on it,the factor affecting on the period was analyzed and an improved method to increase the filter delay was put forward.Thus,the limit of the precision on the length control was compensated.