Dual-parameter Measurement Design Of Temperature And Depth Based On Optical Fiber Sensing Technology

Fiber-optic sensors based on fiber-optic sensing technology have gradually attracted attention in the detection of complex environments because of the unique properties of the material.The ocean is rich in resources,which can effectively alleviate the current situation of global resource shortage.In recent years,the state has gradually paid attention to the position of the ocean in the field of national defense,put forward the ‘marine power strategy’,gradually developed a variety of methods of using optical fiber sensors to detect the interior of the ocean,and achieved a lot of results.Based on the previous research results and the current research hotspots of fiber optic sensors,the main work of this thesis is to develop an oceanographic Temperature-Depth instrument based on fiber optic sensors.The first is the development of the optical fiber temperature and depth sensor.Based on the optical fiber sensing technology,the fiber Bragg grating temperature measuring structure and the Fabry-Perot interference cavity pressure measuring structure are designed,fabricated and sensitivity measured.In order to cope with the complex temperature changes in the ocean,five fiber Bragg gratings with a center wavelength difference of 2 nm were cascaded at an interval of 1 meter,and it was found that five mutually cascaded fiber Bragg grating sensing structures could respond to the temperature changes of the external environment.The correct response is obtained,and the linearity is good.In order to measure the pressure,it is decided to use the extrinsic Fabry-Perot interference structure to measure the external environmental pressure.The material of the diaphragm is simulated by Multi-physical field simulation software,and finally a copper sheet with smooth surface is selected,and then a Fabry-Perot interferometer is formed with the copper sheet and the fiber end face as the core and other components.The structure was found to perform well in water pressure measurement after measurements.Then,the method of fiber Bragg grating sensor demodulation and data reception and processing are studied.Firstly,the demodulation system is studied in detail,and the edge filter method demodulation system is designed.The hardware circuit,software and optical path construction of the demodulation system are mainly designed and manufactured,and the edge filter of long period fiber grating is manufactured.The edge filter suitable for this experiment was selected from two kinds of long-period fiber gratings.Then the scheme was optimized,and the actual temperature test was carried out according to the measured sensitivity coefficient.Finally,the data reception and data processing are completed,and the actual temperature and pressure parameters can be calculated according to the specific sensor wavelength value in cooperation with the demodulator.Finally,the production and practical test of the optical fiber Temperature-Depth instrument were carried out,and good results were obtained.For the fabrication of the thermometer,a new sealing operation,which is different from the sealing operation in Chapter2,has been completed for the temperature sensor and the pressure sensor.The shell of the fiber optic Temperature-Depth instrument was fabricated,and the shape of the shell was improved for the fiber Bragg temperature sensor and the Fabry-Perot pressure sensor to work more efficiently.The data display interface and program made by Lab VIEW software are shown,and the calibration work is finally carried out and it is found that the calibration effect is good,which can be regarded as being able to accurately complete the water pressure measurement of the marine environment within 100 meters.In this dissertation,the fiber optic Temperature-Depth instrument based on the fiber-optic sensor was finally successfully developed.Because the measurement accuracy of the fiber optic Temperature-Depth instrument is directly related to the fiber optic sensor used,it is of great significance to develop a sensor with better sensing performance for the improvement of the instrument performance.