A Study Of Optical Fiber Pressure And Temperature Sensor Demodulation System Based On Scanning Laser

At present,most optical fiber sensing systems heavily rely on spectrometers,broadband sources and other large instrument equipment,and it is difficult to be used widely in industrial fields.In this paper,an optical fiber simultaneous measurement system of temperature and pressure has been designed and demonstrated.The controls of laser wavelength scanning,acquisitions of spectral data and the data demodulations based on Newton least squares fitting algorithm were highly integrated in one system,providing a miniaturized and low cost solution for the measurement of pressure and temperature.At last,the experiments about wavelength demodulation precision,pressure and temperature resolution were made,and the performance of the system was given according to the experiment results.The main study contents of this paper are as follows:1.The development of fiber Bragg grating sensing technology and the demodulation technology are introduced briefly,and the typical multi-parameter measurement schemes are analyzed in this paper.2.The physical structure,sensing mechanism and the pressure and temperature characteristics of fiber Bragg grating are introduced.Analyzing the feasibility of simultaneous measurement of pressure and temperature taking use of the center wavelength and the space of double reflection peaks,which will provide the theoretical support for the following study.3.The hardware design of the system is introduced in detail,including the optical path and hardware circuit.The optical path is mainly composed of circulator,side hole fiber grating and single mode fiber.The hardware circuit is mainly composed of Embedded systems,wavelength scanning lasers,photoelectric conversion,analog-to-digital conversion and acquisition,serial,USB,Ethernet modules.4.The software design of the system is introduced in detail,including the system software process,u/COSIII real-time embedded system,user task,Newton least square fitting algorithm,and PC software.5.Some experiments were made for testing system demodulation precision and the performance of pressure and temperature measurement,including the performance of wavelength scanning laser,the noise of photoelectric conversion and AD acquisition module,wavelength demodulation precision and the resolution of pressure and temperature measurement.The experimental results show that the dual reflection peaks correspond to changes in temperature and pressure with a good linear characteristics,in the temperature range of 10~50? and the pressure range of 0~1.2MPa.The wavelength demodulation accuracy of the system is up to 1pm,corresponding to the resolution of pressure and temperature is up to 0.1MPa and 0.1? respectively.