Software Design For Fiber Bragg Grating Demodulator Based On MEMS Swept Laser

Fiber Bragg Grating(FBG)sensors can be used to measure strain,temperature,acceleration and other physical quantities.Compared with conventional sensors,FBG sensors have advantages of high sensitivity,small size,and resistance to electromagnetic interference,so they win the attention of people and became a hot spot in research.The key technology of FBG sensor is the design of the demodulating system.The detection accuracy of the sensor system is directly affected by the accuracy of the demodulator.Several different demodulation methods were developed in recent years,but some disadvantages such as high price and low sensitivity still exist.So it is of great practical significance to develop a demodulation system with low cost,high sensitivity and stable performance.The main work of this thesis as follows:1.The demodulating technology of fiber Bragg grating is introduced.By comparing the advantages and disadvantages of various demodulation methods,the optical fiber Bragg grating demodulation system based on scanning laser is presented.2.The software for fiber grating demodulator based on MEMS swept laser is designed and developed.Firstly,the software developing platform C++ builder is introduced briefly.Then the principles of the USB protocol and the core functions of USB drive and implementation process are introduced.Finally,the three operating modes of the demodulation system and the implementation of the three modes are introduced.3.The demodulation algorithm is designed and implemented.The principles of several different fitting algorithms are described.And then we test three different fitting algorithms,Gaussian fitting,polynomial,cubic spline fitting in Matlab.The results showed that Gaussian fitting algorithm most effective and accurate.Finally,the demodulation of fiber Bragg grating was realized by Gaussian fitting algorithm based on nonlinear least squares(LM algorithm).The demodulation resolution is 1.72 pm.In conclusion,the software design for fiber grating demodulator based on MEMS swept laser was realized,making the low cost,fast speed,high accuracy and high stability of the demodulation system come true.