Research On Fiber Optic Sensing Network Based On Tdm For Methane Detection

Due to the increasing pressure on environmental protection,natural gas which is cleaner than coal and oil fossil energy is emphasized and extensive used.At the same time,the leaks,explosions and other security incidents of natural gas frequently occur.Gas fiber optic sensor which does not spark in the monitoring process can maximize avoid flammable and explosive gases explosion.But the detection of a single point is not suitable for large-scale using in industry,so the study of gas fiber sensing network becomes hot spots.The research of methane gas based on the theoretical of the sensor network,which analyzes the feasibility of constructing an optical fiber sensor network,the sensor network topology optimization,simulation modeling,building multi-point optical detection network,testing the performance of the sensor network.Firstly,based on Beer-Lambert law and the principle of spectral absorption,the working principle and detection method of single-point gas fiber sensor are studied.The single point methane gas fiber sensor is modeled and simulated by MATLAB.The function of lock-in amplifier is realized by programming and the second harmonic is detected in MATLAB.The gas concentration is linearly related to the peak-to-peak value of the second harmonic in theory.In this paper,based on the single point of detection,the advantages and disadvantages of several typical sensor multiplexing techniques are compared.A methane fiber optic sensing network model which is based on TDM is constructed.Secondly,according to the model,the optical link of the sensing network is designed by using optical circulator,optical splitter.The optical circulator,optical splitter are selected and the construction of network is analyzed.Reflective air chamber is designed.The loss experiment of optical link is studied the remote detection performance of the sensing network.Thirdly,according to the principle of time division multiplexing and harmonic detection,the control and driving circuit of light source and the weak signal processing system are designed,and the hardware design of the phase lock demodulation circuit is completed.Finally,we build a sensor network prototype platform.The experiments which include the principle verification experiment,the detection precision experiment,the response time experiment and the stability experiment are carried out for the sensor network.The experimental results are analyzed.