The Research Of Noise Supperssion And The Design Of Hunman-Computer Interaction On Raman Distributed Temperature Instrument

Compared to other electronic sensors and quasi-distributed sensors,Raman distributed temperature system(RDTS)has the advantage that can accurately measure the temperature at any point along the fiber.It has been widely used in temperature monitoring of gas pipeline,power cable,tunnel and so on.However,it cannot realize the large measurement range and high accuracy simultaneously because of the weak intensity of the Raman backscattering.Based on this problem,two kinds of noise suppression method has proposed.Firstly,though analyze the influence to temperature measurement results of the fluctuation of the optical receiver based on avalanche photodiode(APD),a method of dynamic noise difference algorithm is proposed to calculate the real Raman backscattering intensity,as a result,the sensing distance o is increased from 3 km to 11.5km.Secondly,according to the characteristics of Raman temperature instrument that the temperature is demodulated by the intensity of the backscattering and the advantage of wavelet transform modulus maxima(WTMM)method is suitable for capture singular points of intensity signal,so the method is introduced to Raman distributed temperature system and the fluctuation of measurement temperature is reduced by 4.75?.Meanwhile,based on the two kinds of noise suppression method,though integrated designing the data collection module,data storage module,automatic location and reference position query module,data processing module,warning module,and display module,the human-computer interaction interface of Raman temperature instrument is designed and developed.The main works of this paper are summarized as follows:1)Though analyzing the experiment setup and demodulation method of traditional Raman distributed temperature system,in order to solve the problem that the dispersion is introduced by the different center wavelength of Raman Stokes backscattering demodulates anti-Stokes backscattering method and the problem that claimed strict symmetry of the avalanche photodiode and amplifier,the Raman anti-Stokes self-demodulation method is plan to employ,the demodulation theory and location theory of self-demodulation method is researched.2)The noise characteristics of optical receiver based on avalanche photodiode and the influence to the results of Raman measurement temperature are researched.The sensing distance is limited in 3 km by the existed fluctuation of ground noise of optical receiver whose value is 6.26 mV.So the dynamic noise difference algorithm is proposed and the sensing range increase from 3 km to 11.5 km effectively in the premise that the accuracy of temperature measurement is ensured at 0.83?.3)The results demodulated by Raman anti-stokes self-demodulation way and Raman stokes light demodulate Raman anti-stokes way is contrasted and analyzed by experiment.Because of the dispersion in Raman Stokes demodulates antiStokes method,Raman self-demodulation method is used and the accuracy of the measurement temperature is improved by 14.78?.4)The principle and implementation of wavelet transform modulus maxima de-noising method is studied.And the de-noising ability of wavelet transform modulus maxima is analyzed by experiment.Because of the characteristics that wavelet transform modulus maxima method is suitable for capture singular points of intensity signal,the peak-to-peak value of temperature fluctuation decreased from 5.98? to 1.23? after the wavelet transform modulus maxima de-noising method at the end of the optical fiber.5)Raman distributed temperature system experiment is set up.The dynamic noise difference algorithm,wavelet transform modulus maxima de-noising method and self-demodulation method is applied to the system.As a result,1.58? temperature accuracy,1.66? temperature fluctuation,2.1 m spatial resolution is achieved at 11.5 km long sensing distance.6)A human-computer interaction interface of distributed optical fiber temperature instrument based on Raman backscattering is designed.The humancomputer interaction interface can control the acquisition card,store and call the data,search the reference position automatically,de-noising the signal by the wavelet modulus maxima method,extract the dynamic ground noise and calculate actual intensity,demodulate the temperature,display the temperature,etc.The outdoor experiment of Raman temperature instrument is researched,and the well stability and real-time performance is proved.