Abstract:To improve the transmission performance of conventional MachZehnder interferometer(MZI) filter, a novel filter adopting two resonator rings combining with MZI was proposed. Based on this structure, the filter’s transfer function was established by using the signal flow graph method and the output spectra were simulated as well. The results show that, compared with conventional MZI filter, when choosing appropriate coupling coefficient, the improved filter can give rectangular waves approximating flat top. The free spectral range up to 19nm, the sharpness factor of 1.16, the extinction ratio of 54dB and the quality factor of 94.5 were obtained, thus the transmission performance of this novel filter is improved obviously.The impact of the coupling coefficient and the radius of ring resonator on the output performance of this filter is discussed in detail.