The tension of fiber winding is one of the important factors in the performance of fiber. It is particularly necessary to measure the tension during the fiber winding process and to monitor the fiber tension after winding. This article adopts the method of optical fiber winding and uses OFDR (Optical Frequency Domain Reflectometry) demodulation technology to simulate fiber winding, and briefly introduces the principle of OFDR technology. Through experiments, the strain distribution of the full range of the fiber is measured. The measurement results are basically consistent with the calculation results.
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.
Aiming to meet the high reliability requirements of fiber optic sensor line layout in aero engine measurements under high temperature and high-speed conditions, a method for fiber metallization protection and installation is proposed. A finite element model was established for the welding process of a metallized protective structure, and the thermal-electric-force coupling method was used to simulate the evolution of the temperature field. The research shows that by applying pulse current, the inner temperature of the tube gradually exceeds the outer temperature. Therefore, in order to protect the internal fiber, it is necessary to increase the intensity of the pulse current as much as possible and shorten the duration of the pulse current.
In the aviation field, the instrument must be small, light, and vibration resistant. A Fiber Bragg Grating (FBG) sensor interrogator with a linear variable filter (LVF) can be well suited for the requirements in the aviation field, due to its special optical structure. Moreover, it has a great prospect of applications in the aviation field. An error model is established and the simulation results show that the inhomogeneous illumination of the incident light has an impact on the sensitivity of the interrogator. This paper defines the degree of inhomogeneity to describe the effect of inhomogeneous illumination. Using this model, the design of the interrogator can be optimized to improve its sensitivity.
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