Temperature-Insensitive Embedded Metal-Packaged Fiber Bragg Grating Inclination Sensor

Commercial fiber Bragg grating (FBG) sensors typically rely on require plastics, acrylates or glues for encapsulation and adhesion, making them susceptible to aging, creep, and high-temperature intolerance. To overcome these issues, this study introduces an electrochemical deposition process aimed at creating adhesive-free sensors by embedding FBGs into metal structures. This approach enhances the operational range and lifespan of the sensor. The embedding method facilitates the detection of bending strains by the FBG. Consequently, a temperature-insensitive inclination sensor is designed and fabricated. Two FBGs are embedded on either side of a metal strip, precisely aligned with its central axis, to measure bending strain. When bending stress is applied to the metal steel, the two FBGs experience opposite strains, causing their central wavelengths to drift in opposite directions. Analyzing the wavelength shift difference between the two FBGs yields a sensor with higher inclination sensitivity and temperature insensitivity. The experimental results indicate that the designed sensor has a high sensitivity of 42.76 pm/°, resolution of 0.0023°, and linearity of 0.9994. Temperature-response tests demonstrate the excellent temperature insensitivity of the fabricated sensor, allowing for reliable operation in high-temperature conditions. Furthermore, this metal encapsulation method exhibits significant potential for expanding the applications of FBGs.