Abstract:A flat-top interleaver, in which a mirror on one arm of the Michelson interferomefer is replaced by a G-T resonator, is proposed. In the interleaver, the parameters including the channel spacing of 50 GHz, ripple less than 0.05 dB, −0.5 dB passband of 43 GHz (86% of the spacing), −30 dB stopband of 42 GHz (84% of the spacing), and a channel isolation higher than 40 dB, are achieved. This work has been supported by the Program for New Century Excellent Talents in Fujian Province of China, (Grant No.X07204), the Key Scientific and Technical Innovation Project of Xiamen University (Grant No.K70007), and the Science and Technology Project of Education Department of Fujian Province of China (Grant No. JA08138).