提出了一种由两个2×2 和两个3×3 光纤耦合器级联组成的全光纤Mach-Zehnder 干涉仪型波长交错滤波器，由光纤传输理论，得到光谱的输出表达式。分析结果表明：组成滤波器干涉臂的第三对臂长差为第一对臂长差的2 倍时，耦合器分光比取一些定值可得到输出波形通带平坦、透射率形态近似于方波的波长交错滤波器，谱线峰间的波长间隔约1.6 nm。通过实验所得的结果与理论相吻合。

An all-fiber interleaver of Cascaded M-Z Interferometer (CMZI) composed of two 2×2 and two 3×3 fiber couplers with almost rectangular wavelength response was developed by using a new configuration. Based on the principle of characteristics of fiber transmissivity, the complex amplitude output spectra were established and described by the expression using the matrix transfer function. The analytical results indicate that when the third length difference of interference arms is as twice as the first length difference of interference arms, the coupling coefficient of the couplers is some certain values, and then a uniform flattop passband and similarity to square spectral response can be obtained by the configuration. The passband and stopband of optical interleaver are improved remarkably and the interval of peak output power is 1.6 nm. A filter of novel structure is fabricated by using the fused biconical taper technologies in experiment. The experiment results are in good agreement with the analytical ones.