This paper deduces and summarizes the methods of sensitivity enhancement in interferometer based fiber optical sensors, including the derivation of the sensing principles, key characteristics, and recently-reported applications. The modal coupling interferometer is taken as an example to derive the. Fiber-optic sensing (FOS) technology has emerged as a cutting-edge research focus in the sensor field due to its miniaturized structure, high sensitivity, and remarkable electromagnetic interference immunity. Sensors and Actuators A: Physical, 303, Article 111833. 111833 This manuscript is distributed under a Creative Commons Attribution-NonCommercial-NoDerivs License.