Filtering Performances of Cascaded Mach-Zehnder Interferometer with Chirped Path Differences

To enlarge the FSR and improve the band-pass filtering performances of cascaded Mach-Zehnder interferometers(MZIs),chirped path differences,rather than fixed path differences,were used based on the similarity between the principles of a cascaded MZIs and a ladder type filter.A theoretical model for cascaded MZIs with chirped path differences was established by transfer matrix method.The variations of 3dB bandwidth and FSR were analyzed.The analysis results show that wider FSR and narrower 3dB bandwidth of cascaded MZIs with chirped path differences can be obtained with an optimized chirp coefficient,and that the optimal chirp coefficient increases with an increase in diffraction order.