“…In recent years, optical Mach-Zehnder interferometer (MZI) sensors have attracted increasing attention due to their high sensitivities and simple structures. More and more novel structures are used in optical MZI sensors, such as core offset fusion [1], twisting [2], coating [3], etching [4], and tapering [5][6][7]. Various parameters can be measured by optical sensors, such as temperature [8], humidity [9], refractive index [10][11][12], liquid level [13], strain [14], and so on.…”