Mach–Zehnder Interferometer Mesh for Improved Refractive Index Sensing

We present the analysis for a Mach–Zehnder interferometer (MZI) mesh for refractive index sensing. We configure the mesh to be made from single-mode identical directional couplers forming coupled and cascaded MZIs. The design allows multiple input and output configurations yielding different intensity variations with refractive index at the output ports, thereby with more simultaneous measurements and improved estimate for the refractive index of a sample. The variation of intensity at the output ports due to fluctuations at the input and variation in coupling strengths of the directional couplers is incorporated in our estimates. This extensible and robust geometry should be useful for designing portable sensor configurations.