Comparative Analysis of the Brillouin Frequency Shift Determining Accuracy in Extremely Noised Spectra by Various Correlation Methods

Using the same extremely noised data, two correlation methods for finding the maxima of Brillouin spectra are compared. The first method is a well-known method of correlating the received signal with the ideal Lorentzian function. In the second method, developed by the authors earlier, instead of the Lorentzian function, the same spectrum under study, but inverted along the frequency axis, is used (Backward correlation method, BWC). In addition to evaluating the accuracy of both methods, they are compared with the classical method of Lorentzian curve fitting. The accuracy of the considered methods is estimated depending on the probability of artefacts appearing in the Brillouin scattering spectra. It is shown that when the 9% probability of the artifact occurrence is exceeded, the BWC method shows better results than the other methods considered.