The linewidth enhancement factor of a semiconductor laser with moderate and strong feedback was measured by means of folding algorithm based on the optical feedback self-mixing interferometry. The factors affecting the accuracy of the folding algorithm,including the factor of optical feedback level,nonlinear motion of the external target,sampling frequency and location of turning points,was analyzed by processing the simulated signals.It was shown that optical feedback level factor was the premise of accurate measurement of linewidth enhancement factor and the error caused by nonlinear motion of external target could be reduced by using middle interference fringes.The folding algorithm was improved,providing a helpful measure for signal processing.%为了提高对称折叠算法的精度,通过对仿真信号的测量,分析了影响算法精度的几种因素(光反馈水平因子,外腔的非线性运动,抽样速率和转折点的定位),并且给出了改进方法.仿真结果表明,在测量线宽展宽因子之前,需保证光反馈水平因子的准确测量,利用中间干涉条纹进行测量可以减少外腔非线性运动所带来的误差.这一结论对利用对称折叠算法处理实验信号有一定的帮助.
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