Study On Fiber Grating Demodulation System Based On Tuned DFB Laser

With the development of structure detection technology, the requirements for the automation and intelligence of monitoring system are improved to a higher step, so the requirements for the sensor performance are improved too. Traditional sensors have limitations in structure detection, however the fiber bragg grating (FBG) take application widely because of it's unique advantages of information absolute coding on wavelength and constitute quasi-distributed network easily, so FBG wavelength signal detection become hotspot.A demodulation scheme based on distributed feedback (DFB) laser dynamic scanning FBG is put forward, which based on the advantage of DFB laser with narrow bandwidth and wavelength tunable. The fiber bragg grating sensor mechanism and demodulation system wavelength calibration technology and interpolation algorithm have been first discussed. Determine the technical parameters of DFB laser that was controlled by tuning circuit .A demodulation system have been constructed based on Fabry-Perot etalon for wavelength calibration. The amplifier circuit with low noise and high magnification have been designed and debugged. The data collection program based on PCI data acquisition card have been written by Labview. The precision of peak search have been improved by optimize the direct comparison method. FBG center wavelength have been calculated by piecewise linear interpolation method and the wavelength have been calibrated at the same time. Algorithm have been programmed and M files have been compiled by Matlab. Labview call algorithm program have been realized through Dynamic Link Library.The demodulation system based on DFB laser dynamic scanning FBG have been developed. The resolution of system is 1pm, accuracy is±10pm,the measurement range is 1550.012nm~1554.812nm,wavelength relative changes less 0.32% within 120 minutes. Temperature and strain sensor experimental system have been build based on FBG and experiments research have been taken. The experimental results conform to the theoretical results have been found, the demodulation system can be applied to FBG wavelength signal detection have been verified.