Optical Fiber Sensors Based on Core-Offset Structure: A Review

This review focuses on the preparation methods and wide applications of optic fiber sensors based on core-offset structure. Firstly, the classification and preparation methods of core-offset structures are introduced. Then, the applications of different types of sensors based on the core-offset structure are investigated, including the measurement of physical parameters such as temperature, strain, refractive index (RI), bending, magnetic field by Mach-Zehnder interferometer (MZI), cascaded sensor, long period fiber grating (LPFG), fiber Bragg grating (FBG), Fabry-Perot interferometer (FPI) and Surface plasmon resonance (SPR). Compared with the traditional fiber sensor, core-offset structure sensor with a non-axisymmetric characteristic has excellent sensing characteristics, especially in the recognition of bending direction and high RI sensitivity. Furthermore, the design scheme, working principle and sensing characteristics of different core-offset sensors are also briefly described. Finally, the existing challenges and development direction of optic fiber sensors based on core-offset structure is discussed and prospected.