Research on Calibration Method of FBG Demodulation System

摘要

Calibration is a key issue in the fiber Bragg grating (FBG) demodulation system, through which wavelength, strain, temperature and other parameters can be measured. Because the precision of demodulation system and therefore the results are directly affected by the calibration method, it is significant to develop proper calibration method. In this paper, a new real-time calibration method based on widely used tunable Fiber Fabry-Peort Filter is presented. The principles of the FBG demodulation system and the real-time calibration technique are introduced. A comb filter is proposed by integrating FBGs, through which all reflected waves become narrowband and symmetry. The comb filter is kept in constant temperature environment to serve as a reference FBG. When the system works, it will scan synchronously the measurement FBG and the reference FBG. The wavelength is obtained through real-time calibration of the measurement FBG with reference FBG. This real-time calibration method not only effectively overcomes the wavelength changes of interpolation algorithm by increasing the resolution of modulating range. In addition, the influences of the nonlinearity of FF-P filter driving component on system precision are reduced. With this new calibration method, the precision of demodulation system is improved to ±2pm. The precision of the system is verified by experimental data.