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A long-distance measurement system is proposed in this paper, which is based on optical sampling using a femtosecond fiber laser. The measurement principle and the importance of dispersion compensation are theoretically analyzed in the time domain. By sweeping the repetition rate periodically, stable cross-correlation patterns are acquired, and the unknown distance can be calculated from the interference information. A long optical delay line is placed in the signal path, which can eliminate the “dead zone” effect and improve the performance of long-range measurement. The experimental results show that the present system can realize an accuracy of 4 μm over a 60-m distance, corresponding to a relative precision of 6.7 × 10^-8. The all-fiber optical path system provides a balance among long range, high resolution, and rapid measurement, with the potential for the development of instrumentation for precision engineering applications.