Phase-tunable N-cascaded Mach-Zehnder interferometers using external adjustor

Phase-tunable N-cascaded Mach-Zehnder interferometers (N-CMZIs) are presented and demonstrated experimentally. The theoretical model of the N-CMZIs is established by using the coupled-mode theory and the transfer matrix method. The optimization of single and three-CMZIs based on the Silica-on-Silicon (SoS) are given. The CMZIs based on three-CMZIs and single-MZI are fabricated, respectively, by using the SoS processing and their characteristics are measured. The testing results show single-CMZIs with the insertion loss of less than 5.6 dB and the extinction ratio in output spectrum of 19 dB under the FSR of 0.8 nm and three-CMZIs with the channel spacing of 100 GHz have the top width of ~0.35nm under the wavelength jitters of 0.9 dB, respectively.