<p>To save the cost of the fiber grating sensing technology demodulation equipment and broaden the range of its detection application, one heterogeneous fiber grating spectrum separation (HFGPS) method based on transfer matrix and the adaptive algorithm is proposed. First, a theoretical mode of the HFGPS method is introduced. Second, simulation experiment on linearly chirped fiber Bragg grating (LCFBG) and fiber Bragg grating (FBG) is carried out to obtain the separation effect. After simulation experiment data analyses, relative errors between the separated spectrum signal and the heterogeneous original signal are no >5.29 % , which occurs at spectrum fringe region of FBG and LCFBG, and the separation algorithm can achieve single wavelength or multiwavelength mixing heterogeneous spectrum efficient separation with high precision. Lastly, the temperature calibration experiment is carried out on FBG temperature sensor and LCFBG to further verify the effect of the HFGPS method. After the temperature experiment data analyses, the result shows that sensitivity relative error of FBG between original and heterogeneous separated is 0.4%, and the HFGPS method can achieve heterogeneous spectrum efficient separation and has small influence on the detection performance of the FBG sensor. All these experiment data confirm that the HFGPS method can achieve effective heterogeneous spectrum separation with high precision and has certain practical application value.</p>
Decomposing the tangential force which impacts on the fiber into radial forces and utilizing optical fiber line force model, one novel temperature insensitivity fiber Bragg grating (FBG) torsion measurement model is proposed in this paper. Basic principle of this torsion measurement model is that center wavelength shift of FBG is analyzed to obtain the torsion angler of optical fiber. In order to get the angle of torsion per unit length resolution of this measurement model, simulation experiment is carried out. Results of the simulation experiment show that torsion angle resolution of this measurement model changes from -1.76·10<sup>-3</sup> rad to 2.36·10<sup>-2</sup> rad with detection range ±0.5rad. The demand of the torsion measurement model is just one embedded FBG which decreased the torsion detection expense greatly.
The purpose of conventional techniques for multiplexing fiber Bragg gratings (FBGs) is that each FBG has its own wavelength or unique intensity of reflected light. The cost pf per channel is at least of a few hundred dollars. All these limit the FBG points increasing at fiber measuring system. Based on improved Fast-ICA and self-adapting, this paper focuses on the separation of two same wavelength FBGs mixing model caused by temperature and vibration. Simulation experiment is carried out based on the initial wavelengths of two FBGs are both 1550.515nm and the temperature fluctuation range is 0-0.5°C and amplitude and frequency of exterior vibration are 0.01nm and 10Hz. Simulation data show that the separation steps consume 1.3884s and mean and mean square of absolute errors between the original and separated signals are 8.11·10<sup>-9</sup>, -5.83·10<sup>-12</sup>, and 2.57·10<sup>-6</sup>, 2.42·10<sup>-9</sup>, correspondingly. Therefore, through using this separation method, two same wavelength FBGs could achieve simultaneously measurement of temperature and vibration at one channel. This could double measuring points of fiber detection system, effectively.