基于光纤环结构的微波光子滤波器

针对微波光子滤波器中光纤环的不同参数和结构，详细分析了不对称耦合比对光纤环构成的滤波器抑制比性能带来的提高，并理论推导和实践了光纤环滤波器的级联.研究发现，基于不对称耦合光纤环结构的微波光子滤波器比基于对称耦合光纤环结构的微波光子滤波器拥有更高的抑制比；从原理上分析了无限脉冲响应（IIR）滤波器级联特性不稳定的原因，并在实验中证明了基于低相干光源的级联滤波器频响稳定性有很大提高；对于基于光纤环结构的微波光子滤波器，无论是单环结构还是级联结构，使用宽带光源作为载波会得到更好的滤波效果，系统的频响也更稳定.

Microwave photonic filters based on fiber ring structures

Deduced and tested under different structures and parameters of fiber rings, microwave photonic filters based on fiber ring structures were found out to have better performance with asymmetric coupling ratio and when cascaded.  Experimental results show that microwave photonic filters based on fiber ring structure with asymmetric coupling ratio present higher extinction ratio than those with symmetric ones. The  unstable factors of cascaded IIR filters were also analyzed. The results show that microwave photonic filters based on two cascaded fiber ring structures using low coherence optical source are more stable than those using coherent optical source. Moreover, no matter  the microwave photonic filters are constructed with single fiber ring or cascaded fiber rings , the using of broadband optical source gives the system  better filtering performance and  more stable frequency response.