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频率调制连续波(FMCW)反射计以其高动态范围和窄的空间分辨率优势,在光网络检测、集成光路诊断和光纤传感等领域有着广泛的应用前景。在介绍FMCW反射计基本原理的基础上,分析了光源扫描重复频率、光源功率与FMCW反射计检测距离之间的关系,并探讨了光源相干长度和相位噪声对检测距离的影响。理论分析表明,当待测光纤的长度接近光源的相干长度时,中频信号和相位噪声之间的信噪比会急剧下降,所以FMCW反射计要使用高相干性的光源和一定的相位噪声补偿方法才能应用于长距离的光纤检测。
Frequency modulated continuous wave (FMCW) reflectometer with its high dynamic range and narrow spatial resolution advantages in optical network detection, integrated optical path diagnosis and optical fiber sensing and other fields have a wide range of applications. Based on the introduction of the basic principle of the FMCW reflectometer, the relationship between the repetition frequency of light source scan and the detection power of the FMCW reflectometer was analyzed. The influence of coherence length and phase noise of light source on the detection distance was also discussed. Theoretical analysis shows that when the length of the optical fiber to be measured is close to the coherence length of the light source, the signal-to-noise ratio between the intermediate frequency signal and the phase noise will decrease drastically, so the FMCW reflectometer needs to use a highly coherent light source and a certain phase noise compensation method Can be applied to long-distance optical fiber testing.