Fiber Optic Sensor Based On Double Parameter Mode Coupling Between The Optical Fiber And Intervention

As an important branch of modern sensor technology, the optical fiber sensor has many advantages than traditional sensors in many fields, such as high sensitivity, corrosion resistance, resistance to electromagnetic interference, for remote and real-time monitoring, etc. In recent years, it has been widely researched and concerned. High precision, long distance, integration, network, multipoint parameter measurement become the trend of development in recent years. In this paper, based on the theory of modes recoupling and interference, the research based on Michelson interferometer (Michelson), optical fiber Bragg grating (FBG) cladding mode coupling, Mach-Zehnder interferometer (MZI) sensor, including the following:The first chapter mainly introduces the research background and the characteristics of optical fiber sensor and its application development status.Starting from maxwell’s equation, expounds the concept of light modes, and deduced the interference conditions, enumerates several kinds of fiber optic interferometer, introduces its working principle, advantages and application scope.Design a kind of optical fiber temperature probe sensor based on Michelson interferometer, including the sensor design and the manufacture principle, the experiment results show that the sensor can measure up to600℃, with the sensitivity of120pm/℃, the temperature measurement error is less than3℃, with the linearity of99.7%.Design a temperature and refractive index sensor based on Bragg grating (FBG) and cladding mode coupling, study the sensitive features with cladding modes of the FBG and refractive index of fiber core mode, respectively. Experiment results show that by measuring the energy change of cladding mode and the resonant wavelength shift of FBG can realize measurement temperature and the refractive index at the same time, from25℃to70℃in the temperature range. The sensitivity of temperature with the sensor is10pm/℃, within the refractive index scope from1.33to1.44, the sensitivity of refractive index is83.97nW/RIU.Design a sensor based on the Mach-Zehnder interferometer (MZI) with functions of temperature calibration for measure tension and bending. The experiment studied the formant of FBG wavelength and interference spectrum changed with the temperature, tension and bending, the results shown that the sensor can realize temperature and tension, or temperature and bending at the same time.