Wide-Range Displacement Sensor Based on Common-Path FPI for High Temperature Application

This letter presents a novel common-path FabryPerot interferometer (FPI) utilizing a cone-shape cavity and an in-fiber collimator, for wide-range displacement sensing with temperature compensation. By precisely controlling cutting craft and fusion splicing parameters, a cone-shape cavity and an in-fiber collimator are integrated, enabling propagating beams to be split and transmitted over a wide-range in a parallel manner. In the presence of an external reflector, an External FabryPerot Interferometer (EFPI) is implemented for displacement sensing, while an Intrinsic Fabry-Perot Interferometer (IFPI) is utilized for temperature sensing. Experimental results demonstrate a displacement sensing range of up to 45.3 mm and a temperature response of 1.8 nm/degrees C (wavelength shift sensitivity: similar to 13 pm/degrees C) within the range of 50-600 degrees C. Temperature compensation is achieved through constructing a cross matrix. With its wide-range displacement monitoring capabilities, high temperature survivability and enhanced robustness, the proposed sensor exhibits significant potential for applications in structural health monitoring.