Research On Optical Fiber Temperature And Pressure Sensor Based On Interference Principle

Optical fiber sensor technology has been studied for half a century and established numbers of superior performance. Fiber sensor has been widely used in the field of aerospace, civil infrastructure, transportation and the biomedical sciences because of its advantages such as the low mass, high reliable the advantages of high sensitivity, resistance to electromagnetic interference, and can realize the narrow space, extreme hard environment sensing tasks. Interferometric fiber optic sensor is an important part of fiber sensors. Based on measuring the phase change of light traveling in an optical fiber, accurate information in the environment can be achieved, so as to get the purpose of sensing by detecting the modulated optical signals. Interferometric fiber optic sensor for its variety structure, high sensitivity advantages are widely used in the detection of large number of physical quantities. In this paper we designed three kinds of novelty fiber sensor based on the principle of Fabry-Perot interference and the in-line Mach-Zehnder interferometric for temperature and pressure measurement.1. A miniature Fabry-Perot interferometer is proposed and experimentally demonstrated for temperature measurement. Firstly, the excellent properities and the methods of preparation of grapnene are fully analysized. And then, the method of chemical vapor deposition (CVD) in ambient pressure is introduced in details. Finally, based on this new type of carbon nanomaterials, a miniature Fabry-Perot interferometer is proposed and experimentally demonstrated for temperature measurement. The cavity of the interferometer is a small air gap between the end-face of a single-mode fiber and an ultrathin graphene. A well-defined interference spectrum is obtained, and the dip wavelengths are employed to demonstrate the temperature change. Due to the smart intrinsic characteristics of the graphene film, the proposed device can measure the temperature up to 1008℃, and shows an ultrahigh sensitivity of 1.56nm/℃ and 1.87nm/℃ at the temperature range of 500℃-510℃and 1000℃-1008℃, respectively, making it a good candidate for high-temperature monitoring in the harsh environment.2. An in-fiber Mach-Zehnder interferometer(MZI) for temperature measurement is fabricated. The sensing head has a single-mode fiber sandwiched between two short sections of dispersion compensation fibers with small-core (i.e. DCF-SMF-DCF MZI structure). The results show that the interference dips are sensitive to ambient temperature. The fiber device we proposed is invariable thermal sensitivity for a range of temperature fluctuation from 30℃ to 200℃ and obtains a temperature sensitivity of 45pm/℃. Finally, the type of sensor has advantages of compact structure, good temperature response linearity.3. A miniature Fabry-Perot interferometer is fabricated by the use of graphene diaphragm for pressure sensing with the sensitivity of 104nm/MPa. On the other hand, the ability of temperature measurement is also tested and presents excellent temperature responses of 1.48nm/℃.