Design And Application Of Multi-channel High Speed Demodulation Software For FP And FBG

With the development of optical fiber sensing technology,point optical fiber sensor has been widely used in transportation,construction,medicine,aerospace,industrial and military fields,because of its excellent insulation,anti-electromagnetic interference,small size,light weight,high sensitivity and easy installation.The most widely used sensor are FP and FBG.But at the same time,there are still many problems need to be solved.Such as the two sensor always need to be used simultaneousle but the existing optical fiber sensing and demodulation system can only demodulate FBG.The demodulation accuracy,demodulation speed and demodulation system parallel processing channels of the exiting demodulation system can not meet the needs of industrial applications.In some special conditions such as high temperature the effect of sensor temperature calibration is not ideal and so on.Therefore,it is of great theoretical and practical significance to improve and perfect the optical fiber sensor demodulation system and demodulation software.Based on this,this paper has completed a series of work,summarized as follows:Firstly,Based on the scanning of semiconductor lasers to build a 16-channel demodulation hardware system,which can demodulate the optical fiber F-P sensor and FBG at the same time.The acquisition speed can reach 1KHz.Then,do a detailed demand analysis,data format and process of the demodulation software system.We also proposes a channel expansion method,which makes the hardware module based on the 16 channel to build the system of the 32 channel,the 48 channel,the channel of the 64 or more channels,and analyzes the software implementation of the channel expansion technology.Secondly,the spectrum demodulation,phase demodulation and the demodualtion of fixed-point wavelength for Fabry-Perot sensor are implemented.The FFT algorithm and CZT algorithm are implemented for phase demodulation of FP,and the advantages and disadvantages of the two algorithms are compared and analyzed in detail.In view of the high time consuming of CZT algorithm,multi-thread technology is used to optimize the demodulation speed,and the CEvent in MFC is used to synchronize the thread.The realization of F-P sensor demodulation precision for phase demodulation speed under the condition of 0.0001 rad 960Hz.The low-pass filtering of the spectrum of the Fabry-Perot sensor is carried out,and the high-frequency white noise signal in the signal is filtered out.The phase unwrapping and the sliding averaging filtering are performed on the demodulated phase.The demodulation algorithm of FBG sensor is written so that the system can process FP sensor and FBG sensor at the same time.The temperature calibration method of polynomial temperature at high temperature and the corresponding point temperature calibration algorithm are realized.The system can reduce the influence of temperature on the signal of FP sensor at high temperature,and obtain only the change of phase caused by strain.Using the map container in C++ STL to optimize the corresponding point temperature calibration algorithm.Also we achieved the pressure demodulation algorithm.Thirdly,using C++ in the Microsoft Visual Studio 2008 VC ++ integrated development environment to complete the demodulation software function development work,and with Measurement Studio 8.6 completed the graphical display interface development work.The function of the system is tested and the performance of the system is tested.A large number of experiments show that the system has good stability and repeatability.And has successfully used in many actual projects.