延时自外差法线宽测量误差分析仿真及修正

讨论了移频延时自外差探测的基本原理,并对外差得到的功率谱进行了公式推导。在此基础上,对外差测量中出现的测量误差进行分析,同时设计了自外差测量实验装置进行实验对比,确定了由于延时线长度不够导致的线宽测量误差来源是因为延时时间短导致幂指数函数项波动加剧造成的;同时针对外差信号频谱为洛仑兹型和类高斯型的混合谱型,在高斯功率谱密度函数的基础上,对延时时间和1/f谱宽的影响进行了仿真计算,采用Voigt分析,提取出1/f导致的测量误差,提高了线宽测量的精度。以高斯谱宽4.5 kHz的谱型为例,对应的洛仑兹线宽约为0.68 kHz,提高了一个数量级的测量精度。

Laser Linewidth Measurement Error Analysis and Correction on Fiber Delayed Self-Heterodyne Interferometer

The linewidth measurement error of delayed self-heterodyne interferometer is described in detail. The fundamental using delayed self-heterodyne to measure laser linewidth is analyzed, the emulator is programmed and an experimental setup is constructed to measure laser linewidth, when shorter delayed fiber is adopted. The result shows the measurement error result from the fluctuation of power term. From numerical analysis, the power spectrum resulting of self-heterodyne signal is Voigt profile and the 1/f frequency noise is shown to be approximately Gaussian. The effects of 1/f frequency noise on self-heterodyne detection are described and the results are applied to the problem of laser linewidth measurement, It is proved that method is an effective tool for reducing the measurement error. As the example, when the spectrum width of Gauss profile is 4.5 kHz, the Lorentzian spectrum width is 0.68 kHz, the improvement is abvious.