为实现同时具备宽带可调谐、单透射峰、窄滤波带宽三大特征的高性能微波光子滤波器,设计了一种基于2×2光纤耦合器的环型谐振腔,推导、仿真并实际测量了该谐振腔的输出特性,最终与普通光滤波器相结合实现了高性能微波光子滤波器。实验结果表明,该光纤环谐振腔其滤波带宽可低至1.2 MHz,与普通可调谐光滤波器级联后可实现任意单透射峰的动态选择,通过相干探测链路实现了40 GHz范围内可调谐的光载射频信号。与传统非腔体微波光子滤波器相比,该方法明显降低了滤波带宽;与单一光纤环谐振腔相比,该方法能够实现任意单透射峰的动态选择。这一滤波器有望用于未来超精细光谱分析、光纤传感等领域。

This study designed a ring resonator based on a 2×2 fiber coupler to create a high-performance microwave photonic filter with tunable broadband, single transmission peak, and narrow filter bandwidth. The output characteristics of the resonator were deduced, simulated, and measured. The high-performance microwave photonic filter was realized by combination with an ordinary optical filter. The experimental results show that the filter bandwidth of the designed fiber ring resonator can be as low as 1.2 MHz. It can realize a dynamic selection of any single transmission peak after cascading with the common tunable optical filter. The optical RF signal can be tuned to 40 GHz through a coherent detection link. Compared to that with a traditional noncavity microwave photonic filter, the proposed resonator significantly reduces the filter bandwidth. Meanwhile, compared to the single-fiber ring resonator, the proposed resonator can realize a dynamic selection of any single transmission peak. The designed fiber ring resonator is expected to be used in ultra-fine spectral analysis and optical fiber sensing in the future.