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Phasor Notations-based Simple Analytical Method for an Intuitive Design of Wavelength Interleaver with Flattop Response

Abstract Mach–Zehnder interferometer (MZI)-based wavelength interleaver is an important device for wavelength multiplexing in dense wavelength division multiplexed optical communication systems. An MZI-based wavelength interleaver can be realized by concatenating 2×2 directional couplers through differential delay lines. The importance of the location of the second delay line in a 2-stage MZI-based wavelength interleaver, and its implication on the optimum value of the splitting ratios of the couplers, to achieve a flattop wavelength response, is highlighted. Here a novel method based on phasor notation to estimate the appropriate magnitude and location of the differential phase delay, and its dependence on the splitting ratios of the couplers is presented. The applicability of the method has been illustrated through analytical equations and simulated responses. The approach gives a better intuitive understanding of the working of interleavers, which is crucial in fabricating a practical wavelength interleaver with flattop response.