An accurate and rapid method for extracting parameters from multi-peak Brillouin scattering spectra

• Multi-peak spectrum can realize temperature and strain measurement simultaneously.
• How to extract the multi-peak parameters accurately is difficult.
• A parameters extraction method for the multi-peak Brillouin spectrum is proposed.
• The proposed method can guarantee convergence and obtain parameters accurately.
• The computation time of the proposed method is similar with other methods.

To improve the accuracy of the simultaneous measurement of temperature and strain from Brillouin scattering, an accurate and rapid method for extracting parameters from multi-peak Brillouin scattering spectra is proposed. First, a Brillouin scattering spectrum that contains multiple peaks is segmented into several single-peak signals. Second, approaches such as linear least-squares fitting are used to obtain the initial values for the parameters of the Brillouin scattering spectrum. Finally, the Levenberg–Marquardt algorithm is used to minimize the objective function based on a nonlinear least-squares fit. The proposed method and three other typical methods are implemented and applied to simulated signals with different signal-to-noise ratios and to two real signals acquired by a Brillouin optical time-domain reflectometer. The results reveal that the random method easily diverges. The harmonic reconstruction method is sensitive to noise. The individual peak fitting method has significant errors when it is applied to multi-peak signals. However, the proposed method rapidly converges to the optimal solution and is the most accurate of the four methods. The proposed method solves the problem of extracting parameters from multi-peak Brillouin scattering signals rapidly and with high accuracy. Additionally, the proposed method provides the technical capability to simultaneously measure temperature and strain.