Fiber optic interferometers to sense various physical parameters including temperature, strain, pressure, and refractive index have been widely investigated. They can be categorized into four types: Fabry-Perot, Mach-Zehnder, Michelson, and Sagnac. In this post we will explain the basics of interferometry and the different types of existing interferometers. Common interference structures include the Mach-Zehnder interferometer (MZI), Michelson interferometer, Fabry-Perot interferometer (FPI), ring resonator interferometer, and. In Fourier transform spectroscopy they are used to analyze light containing features of absorption or emission associated with a substance or mixture.