The Multi-point Sampling Demodulation Of Fiber Grating Based On Fast Tunable Laser Light Source

Sensing technology refers to a kind of information science technology that extracts the required information from the signals of natural sources.It can perform the task of identifying,analyzing and processing this information.The sensing system is usually composed of signal source,sensitive components,signal receiver and signal processing unit.The sensing system whose sensitive element adopts fiber Bragg grating(FBG)and sensing signal is optical signal will be called FBG sensing system.Due to its small size,,high temperature resistance,corrosion resistance,passivity,anti-electromagnetic interference,high precision,long transmission distance,ease of multiplexing and distributed applications,FBG has a wide range of applications in the field of sensing.Fiber grating demodulation technology with Tunable laser light source is one of the signal demodulation technology of FBG sensing system.Based on the modulated grating Y branch(MG-Y)tunable laser light source,this paper designed a demodulation algorithm called “The multi-point sampling demodulation of Fiber Grating based on fast tunable laser light source”.The main content of this paper includes: Analysis of the light source characteristics and technical parameters of the MG-Y laser,the sensing principle of fiber Bragg grating.And by improving the Fabry Perot(F-P)sensing system based on the MG-Y laser,constructed a FBG sensing system based on the tunable laser light source.Theoretical analysis and application analysis of mode coupling theory,FBG dual-wavelength demodulation algorithm,FBG Buneman frequency estimation demodulation algorithm.A demodulation algorithm called “The multi-point sampling demodulation of Fiber Grating based on fast tunable laser light source” is proposed,the related vibration simulator,analog demodulation program,vibration experiment demodulation program and acceleration experiment demodulation program has been written by labview.Refer to the demodulation algorithm of Buneman frequency estimation demodulated based on spectrometer,a demodulation program suitable tunable laser is provided.It is used as a comparison of demodulation results.The problem of the FBG demodulation based on fast tunable laser light source,such as data acquisition delay affecting demodulation accuracy,and sampling value jumps affecting demodulation results,are analyzed.And for these two problems proposed a compensation algorithm to eliminate these negative effects.Propose a vibration detection program,an acceleration detection program and its matching calibration program,and get the expected outcome through experiments.Finally,the theoretical analysis results of the demodulation algorithm are verified by simulation and experiment,and the two algorithms are compared,the future development of the algorithm proposed in this paper is prospected.By the improved algorithm,this paper realized a FBG sensing system based on a fast tunable laser light source.It has many advantages such as large demodulation range,stability,high speed,high precision,self-adaptation and so on.Modularization and subroutine design make the compensation algorithm and the entire demodulation program have a really well possibility of further expansion and development prospects.When the demodulation module running alone,the peak value of the demodulation speed can reach more than 40 k Hz,and the center wavelength error is controlled within 1pm after delay compensation.It has the function of adaptively selecting the sample value,and can complete the demodulation in the center wavelength shift range of 1nm.It also has room for a wider range of demodulation improvement.And at the same time it solves the center wavelength distortion and jump problems which caused by delay and sudden change of sampling value.