Absolute Distance Measurement over a Wide Range Based on Dual Femtosecond Lasers

High precision distance measurement has been playing a very important role in social life, especially in scientific research. We propose a combined measurement scheme based on dual femtosecond lasers for absolute interstellar distance measurement. This method combines time of flight (TOF) with phase measurement in different ranges and accuracy. We use optical equivalent sampling to optimize the accuracy of the phase measurement results. In the meantime, we also use this scheme for dynamic range measurement with high refresh frequency. Respectively, this simulation gives examples of absolute distance measurement and real-time dynamic mechanical displacement measurement. Meanwhile, we analyse the accuracy of this measurement scheme. The simulated probe light source pulse frequency is 100 MHz, the difference between the local oscillation sampling pulse frequency and the probe light source pulse frequency is 100 kHz. Simulation results show that the error of a single measurement using the present absolute distance measurement scheme does not exceed 750 nm within a large range of about 10⁷ meters. The relative distance is refreshed in terms of the minimum resolution length of equivalent sampling, and the maximum error also does not exceed 750 nm. Finally, we explore the error sources in terms of the time jitter of the pulse source, the pulse repetition frequency of the probe and sampling and their differences. In summary, the present measurement method has the advantages of simple principle and easy operation.