Study On Absolute Ranging By Chirped Pulse Interferometry Using Femtosecond Optical Frequency Comb

There are lots of important applications in many fields for high-precision,large-scale absolute distance measurement,such as large-scale equipment manufacturing,spacecraft formation flying,planetary telemetry in astronomy and so on.With the improvement of science and technology production level,people demand a higher range accuracy.Femtosecond optical frequency comb is known for its high frequency stability,wide spectrum width and narrow pulse width,and has been applied to many sophisticated testing fields.In this paper,the application of optical frequency comb in absolute distance measurement is studied,and a method of the chirped pulse interference for measuring the absolute distance is proposed.The main research works are as the following:1.The ranging technology development status based on optical frequency comb are studied,and the characteristics and the classification of a variety of ranging methods using a optical comb are introduced.Point out the limitations of some ranging methods,for spectral interferometry,put forward chirped pulse interference for distance measurement;2.The principle of the chirped pulse by a grating pair and the principle of the chirped pulse interferometry based on the optical comb are analysed in detail,and the factors that affect the range of the distance measurement are also studied,and the paper gives the corresponding simulation.And a set of experimental device is designed,which combines the spectral interference technique and the chirped spectral interference technique,can measure the chirped factor and the chirped pulse width,and can also realize the self calibration of the chirped spectral interference ranging system.3.An improved Michelson structure is built.The experimental results show that the range is affected by the chirp parameters,and the results are consistent with the theoretical simulation results.Large scale ranging experiment is carried out on the long underground rail.The experimental results show an agreement well within 33 ?m in a range up to 65 m,corresponding to a relative precision of 5.1?10-7.In addition,the optimization of the measurement uncertainty is theoretically and experimentally performed,and it is analyzed that the Abbe error and cosine error existing in experimental system.The limitations have been studied about that the ranging methods based on optical comb can not be arbitrary ranging.The scheme of combining long delay line in the reference arm with adjusting repetition frequency is proposed,which can make the reference pulse meet the measuring pulse at any position,so that it can realize arbitrary distance measurement.4.We study on the chirped interference spectra using typical time-frequency analysis methods,and compare the analysis results of different time-frequency transforms.The factors affecting the transform results are discussed,and these methods are used to deal with the range data of the chirped spectrum interference.The experiment comparison shows that the relative precisions of the time-frequency transform methods are all better than 6×10-7 in a range up to 65 m,with respect to the reference He-Ne interferometer data,which meets the high-precision processing requirement.Wherein smoothed pseudo Wigner-Ville distribution,continuous wavelet transform(CWT)and smoothed Choi-Williams(SCW)distribution perform better in processing chirped spectral data and get the expected result.