Absolute Distance Measurement Using Frequency Comb

Optical frequency combs have advanced the field of precision measurement with revolutionary progress since their invention.Long-range absolute distance measurement with high precision and accuracy is of significant importance in both basic science and technology.In 1983,the meter was strictly defined as the length light travels in vacuum during 1/299792458 second,highly uniting the length and the time.Subsequently,scientists all over the world have proposed various methods capable of absolute distance measurement using frequency comb,and frequency comb based absolute distance measurement is still progressing rapidly nowadays.This thesis focuses on the technique of absolute distance measurement using frequency comb.Large-scale distance,up to 80 m,can be precisely measured,which can well satisfy the requirement of the long-range high-precision distance measurement in a wealth of scientific applications.A method based on the intensity evaluation is proposed.The principle of the pulse cross correlation is analyzed,and the theoretical models of Gaussian pulse,Sech² pulse and Lorenz pulse are developed,which can be used to measure the distances.The experimental results show an agreement within 1.5μm in 25 m range,compared with the reference distance meter.The principle of dispersive interferometry is analyzed,and the distance can be measured via the modulation frequency of the interferogram.In particular,a long fiber link is used to realize arbitrary distance measurement,to overcome the limitation of the low-resolution spectrometer.The comparison with the reference distance meter show an agreement within 25μm in 75 m range.To minimize the measurement uncertainty,the optimization of the system setup is performed.The distance measurement can be measured using optical sampling by cavity tuning.The pulse cross correlation patterns can be obtained based on a long fiber link by sweeping the repetition frequency.The peak position of the cross correlation pattern can be measured by Hilbert transform,which can be used to measure the absolute distance.The experimental results show an agreement within 3μm in 60 m range,compared with the reference distance meter.The cross correlation patterns can be also obtained with a Michelson interferometer in the free space.The distance can be measured via Fourier transform.The experimental results indicate an agreement within 4μm in 75 m range,compared with the distance meter.A method of optical sampling by catity tuning is proposed,which is capable of glass thickness and refractive index measurement.A multi-heterodyne scheme by using frequency comb and a single-frequency laser is proposed.The principle is analyzed,and the distance can be measured by the phase of the heterodyne signals with a series of synthetic wavelengths.To improve the stability of the beats,the single-frequency laser is locked to a stable cavity by using Pound-Drever-Hall technique.The experimental results show that the agreement with the reference distance meter can achieve 3μm in 50 m range.In the case of measurement in air,the correction of air refractive index always dominantly contributes to the total uncertainty.To improve the uncertainty due to the air refractive index,a two-color dispersive interferometer is developed.In 12 h long-term experiments,the uncertainty of the air refractive index correction can achieve 3.3?10^-8.Further,the experimental results show an agreement within 3μm in12 m distance range,compared with the reference distance meter.The standard deviation is well improved with the correction of refractive index.