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为了改善常规马赫-曾德尔干涉仪(MZI)型滤波器的输出特性,提出了一种由双耦合器和单模光纤构成的“8”字形谐振环,将该光纤谐振环与一个3dB光纤方向耦合器相结合,利用光纤谐振环反馈回路引入的相位调节效应,选择合适的谐振环耦合角,设计出一种基于对称结构的光纤谐振环梳状滤波器,具有平坦滤波响应的输出光谱。与普通MZI型梳状滤波器和双级级联MZI型梳状滤波器相比,阻带抑制和过渡带滚降特性明显加强;与不对称结构的光纤谐振环辅助MZI型梳状滤波器相比,在考虑传输损耗的情况下,相干涉的两束光信号不存在幅度差异,降低了传输损耗对梳状滤波器消光特性的影响。
In order to improve the output characteristics of a conventional Mach-Zehnder interferometer (MZI) type filter, a “8” -shaped resonant ring composed of a double coupler and a single mode fiber is proposed. The fiber resonant ring is coupled with a 3dB Fiber-optic directional couplers, the fiber-resonator comb filter based on the symmetrical structure is designed by using the phase-adjusting effect introduced by the feedback loop of the fiber-optic resonant ring and selecting the proper coupling angle of the resonant ring. The output spectrum has a flat filter response . Compared with the conventional MZI comb filter and the two-stage cascaded MZI comb filter, the rejection of stopband and the roll-off of transition band are obviously enhanced. Compared with the asymmetric structure of fiber resonator, the MZI comb filter phase When considering the transmission loss, there is no amplitude difference between the two beams of the coherent interfering signal, which reduces the influence of the transmission loss on the extinction characteristic of the comb filter.