Strain distribution sensor based on the fiber Bragg grating

Abstract

W pracy przedstawiono koncepcję czujnika do pomiaru rozkładu naprężenia przy wykorzystaniu światłowodowych siatek Bragga (FBG - ang.: Fiber Bragg Grating). Opisano wykorzystanie metody symulowanego wyżarzania, zastosowanej do rekonstrukcji światłowodowej siatki Bragga, poddanej różnym rozkładom naprężenia. Zamieszczone wyniki analizy wskazują, iż możliwe jest określenie rozkładu naprężenia na bardzo małych powierzchniach rzędu kilku milimetrów.The conception of the simulated annealing method, used to reconstruction of the fiber Bragg grating, is presented in this paper. The fiber Bragg grating was used as a distributed strain sensor. Results and conclusions, which have flown out from our article, prove us that it's possible to determine the strain distribution in the FBG element. In this work the inverse problem technique is used. The inverse problem for our grating is to pass from the grating spectra to the refractive index modulation. We use the global optimization algorithm for solution of the inverse problem. The knowledge about the refraction index modulation phase, in each point of the grating, allow direct definition of the physical quantity (in our case: the strain), which evoke this change. First, we use the transfer matrix method to calculate the reconstructed grating spectrums in different grating parameters, and then we use simulated annealing algorithm to search a reconstructed spectrum that will be in agreement with the measured spectrum