An all-fiber flat-top interleaver of Cascaded M-Z Interferometer (CMZI) using a 2×2 and two 3×3 fiber couplers with approximate rectangular wavelength response was developed.The relationships among the coupling ratios of the couplers
the length difference of interference arms
and the intensity transmission spectrum were analyzed. The results indicate that a uniform flat-top spectral response can be obtained by the configuration when the length difference of interference arms and the coupling coefficient of the couplers are some certain values and the passband and stopband of optical interleaver can be improved remarkably. Compared with conventional CMZI
the most advantage of the present method is that the coupling ratio of couplers can be controlled accurately. Finally
a novel structure of interleaver is fabricated using fused biconical taper technics in experiment. The experiment results agree with the analytical ones well.