Experimental study on nonlinear temperature sensitivity of femtosecond-laser-inscribed Fiber Bragg grating

Previous studies have shown that there is an obvious nonlinear phenomenon between the reflection wavelength and the ambient temperature when measuring temperature of fiber gratings made by UV exposure method. In the range of -30 to 80°C, this article conducts temperature calibration comparison experiments on uncoated fiber Bragg grating made by UV exposure method, the femtosecond-laser-inscribed fiber Bragg grating without coating and the femtosecond-laser-inscribed fiber Bragg grating with polyimide coating, it was found that there is also a nonlinear phenomenon between the reflection wavelength of femtosecond-laser-inscribed fiber Bragg grating and the ambient temperature. However, compared with the fiber grating made by UV exposure method, its nonlinearity is smaller, and on the femtosecond-laser-inscribed fiber Bragg grating with polyimide coating, the nonlinear phenomenon changed abnormally.