Design Analysis of a Novel All-Fiber Mach-Zehnder Interferometer Interleaver

Abstract

In order to improve the output spectrum flatness and bandwidth characteristics of conventional Mach-Zehnder interferometer(MZI) filter, a novel two-stage cascaded MZI interleaver is constructed by adding one 8-shaped fiber ring resonator to the interference arms of a conventional single stage MZI filter. Based on a comprehensive analysis, the output spectrum expression is established and simulated numerically. The results of numerical simulation indicates that when the length difference of interference arms and the coupling coefficient of the couplers are some certain values, it will obtain a uniform flat-top passband and similarity to rectangular output spectrum. The improved interleaver has a wider 0.5dB passband bandwidth and 25dB stopband bandwidth, and the rejection in stopband and the roll-off in transition band are improved remarkably. The device has a certain ability to resist the deviation, which reduces the difficulty degree of making it. The design and analysis should be useful in the realization of flattop all-fiber interleaver for development in dense wavelength division multiplexing (DWDM) networks of high spectral efficiency.