To realize precise absolute distance measurement, an all-fiber beat-frequency laser heterodyne distance measurement system based on a fiber-optic interferometric structure was proposed and demonstrated. An acousto-optic frequency shifter is introduced into one arm of a fiber-optic Mach–Zenhder interferormeter to generate the beat-frequency laser beams in two fiber-optic paths. By a ternary sinusoidal curve fitting method to extract the initial phases of the two beat-frequency laser signals and their phase difference, a distance measurement precision of several tens micrometers can be realized in a distance range of several meters. Experiments showed a maximum relative error of 0.0548% and a resolution of 83.333 μm in a distance range of 0 to 600 mm.

中文翻译：

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全光纤拍频激光外差绝对测距系统

为实现精确绝对测距，提出并论证了一种基于光纤干涉结构的全光纤拍频激光外差测距系统。将声光移频器引入光纤马赫-曾德尔干涉仪的一个臂中，以在两条光纤路径中产生拍频激光束。通过三元正弦曲线拟合方法提取两个拍频激光信号的初始相位及其相位差，在数米的距离范围内可实现数十微米的测距精度。实验表明，在 0 到 600 mm 的距离范围内，最大相对误差为 0.0548%，分辨率为 83.333 μm。