Design of Superstructure Fiber Bragg Grating With Efficient Mode Coupling for Simultaneous Strain and Temperature Measurement With Low Cross-Sensitivity

An efficient fiber-optic sensor based on a superstructure fiber Bragg grating (SFBG) for simultaneous strain and temperature measurement is numerically and experimentally demonstrated. The stain-insensitivity property of a specific LPG resonance band has been used to overcome the effect of cross-sensitivity. The strain sensitivities of the FBG and LPG peaks of the proposed SFBG sensor have been obtained as 0.79 and -0.41 pm/με, and their temperature sensitivities are found as 8.67 and 40.13 pm/°C, respectively. The resolutions for the strain and temperature measurements have been noted as ±12.83 με and ±1.02 °C based on the wavelength resolution of an optical spectrum analyzer (FBG peak: 0.01 nm; LPG peak: 0.1 nm) and the deviations of measured values from applied ones of measurands. The proposed sensor has shown good agreement between the applied and measured measurands with good linearity and reduced cross-sensitivity.