High-tolerance power splitting in symmetric triple-mode evolution couplers

This paper describes the analytic behavior of super-mode propagation in a symmetric triple-mode evolution coupler. Numerical simulations of this new design based on window filter functions are performed. Fabrication tolerances are assessed and checked for several design parameters, which resulted in a higher insensitivity to small design variations when compared to other standard coupler designs, reducing the necessity of individual trimming for applications when accuracy is critical. The use of different power splitting ratios is also demonstrated by means of static and dynamic changes in the design, opening a wide range of possible applications.