为了在提取Lorentzian型布里渊频谱特征时选择最佳模型, 以线性最小二乘法和非线性最小二乘法构造的目标函数为研究对象, 系统地比较目标函数构造对频谱特征提取的影响。数值产生了不同信噪比、扫描频率间隔、g0、vB和ΔvB的布里渊信号, 比较了两种模型得到的频谱特征参数的准确性和计算耗时, 并用真实布里渊散射信号进行了验证。结果表明: 在不含干扰的理想状态下两种模型都能达到非常高的精度, 随着噪声含量/扫描频率间隔的增加两种模型的准确性都下降, 但线性模型明显大于非线性模型, 实际时应采用非线性模型。实验测量的布里渊散射谱信号验证了分析结果的正确性。

To select the best optimization model on parameter extraction in Lorentzian Brillouin scattering spectrum and improve the accuracy of the temperature or strain measurement, taking the objective functions based on linear and nonlinear least-squares fits as the study objects, the influence of the optimization model on the accuracy of the parameter extraction was systematically investigated. Brillouin scattering spectrum signals with different signal-to-noise ratios, scanned frequency intervals, g0, vB and ΔvB were numerically generated. The accuracy and computing time of parameter extraction and temperature/strain measurement of the linear model were compared to that of the nonlinear model. The results reveal that, if the signal is ideal and free from noise, the two models are free of any errors. The errors of the two models will increase with increasing in noise level/scanned frequency interval. However, the error of the nonlinear model is appreciably lower than that of the linear one. In engineering practice the nonlinear model should be selected. The analysis is validated with the experimental Brillouin scattering spectrum signals.