Study On The Fiber Grating Matching Demodulation System With Temperature Compensation

Fiber Bragg Grating (FBG) sensors, because of its excellent feature such as anti-electromagnetic interference, corrosion-resistant, high sensitivity, compact and so on, have been broadly applied in the optical fiber sensing and optical fiber communications. FBG sensor has become the focus in the optical fiber grating sensor field. The demodulation technique of FBG is a key point nowadays in FBG sensor technique. FBG changes the measured information into the motion of reflection spectrum, we can achieve the accurate measurement of small displacement of reflective wavelength by using high-precision optical spectrum analyzer(OSA). However, high-precision OSA is difficult for the actual project for its huge size and high price. So, a high precision and low-cost FBG demodulation technique is needed.Based on research status at home and abroad, this paper designs a reflective demodulation system based on matching grating method. The measured characteristics of FBG demodulation system are consistent with theoretical characteristics by computer simulation. We find that the system has good stability and dynamic characteristics through testing experiment of dynamic characteristics.In this paper, dynamic measurement system of FBG temperature automatic tracking based on FBG demodulation can prevent system static working point of fiber grating moving caused by ambient temperature. We stick the grating on the PZT, and scan PZT voltage, we will find that the center wavelength of the matching grating moves, when the output voltage of system reached the maximum, we will find that the center wavelength of the matching grating and sensing grating matches. The best static working point of system is a half of maximum and minimum output voltage, when the system begins dynamic measurements, static working point is near the best static working point. The computer deal with the data, control the PZT drive power by parallel communication. When the temperature increases from 22℃to 33℃in the temperature-controlled box, even though the temperature changes rapidly, the maximum deviation of static working point is 70mV. So, the system can eliminate the influence that ambient temperature give to sensing grating, and avoid output signal distortion.