Simultaneous vector bending and temperature sensing based on eccentric multi-mode fiber Bragg gratings

Abstract

Abstract Vector bending sensing is a key parameter in posture detection and structural health monitoring. Eccentric fiber Bragg gratings (FBGs), which can measure vector bending and temperature simultaneously, were fabricated by femtosecond laser direct writing in multi-mode fiber. The intensity of the FBG is only sensitive to curvature when the temperature is below 260 ℃. Rectangular structure was adopted to resolve bending direction. The intensity difference of the symmetrically inscribed FBG realizes the multiplication of the bending sensitivity, and the bending sensitivity is 4.42\u2009dB/m-1. In addition, the difference between the two symmetrical peaks eliminates the power fluctuation noise caused by the fluctuation of the light source and the contamination of the fiber end. The wavelength of the FBG is only sensitive to temperature when the curvature is in the range of -2.353\u2009m-1 to 2.353\u2009m-1, and the temperature sensitivity is more than 13\u2009pm/℃.