Fiber-Optic Temperature Sensor Using Differential LP-Mode Delay Measurement in Weakly-Coupled FMFs

In recent years, different kinds of fiber-optic temperature sensors have been widely applied in various areas such as power systems and environmental monitoring, which are typically built based on temperature-induced influences to interferometers, grating structures or back-scattered light propagation in traditional single-mode fibers (SMF). In this letter, we propose a novel temperature sensing mechanism based on weakly-coupled few-mode fibers (FMF), in which signals in different linearly-polarized (LP) modes could propagate independently through the fiber, and the influence of temperature to differential mode delay (DMD) between LP modes are utilized for the sensing. The simulation model is established and the simulative results show a linearly-increased relation between DMD and temperature variations, which are then experimentally verified based on the DMD measurement for different mode pairs in a 4-LP-mode FMF utilizing white-light interferometry scheme. The proposed sensing mechanism could achieve flexible systematic structures and find high potential in various applications.