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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。
In order to select the best model for the extraction of Lorentzian Brillouin spectral features, the objective function constructed by linear least square method and nonlinear least squares method is selected as the research object, and the effect of the objective function construction on the spectral feature extraction is systematically compared. The Brillouin signals with different signal-to-noise ratios, scanning frequency intervals, g0, vB and ΔvB are numerically generated. The accuracy and time-consuming of the spectral characteristic parameters obtained by the two models are compared and the results are compared with the real Brillouin scattering signals verification. The results show that both models can achieve very high accuracy under the ideal condition without interference. With the increase of noise content / scan frequency interval, the accuracy of the two models decreases, but the linear model is obviously more than the nonlinear model. In practice, a nonlinear model should be used. The experimentally measured Brillouin scattering spectrum signals verify the correctness of the analytical results.