Research On Distance Measurement And Velocity Measurement Technology Based On Electro-optic Dual Frequency Combs

Laser measurement technology is an indispensable part of modern science and technology,which has been widely used in industrial manufacturing,national defense,military,satellite navigation and other fields.At present,the traditional laser measurement technology is limited by the light source and detection mode,and has developed to a bottleneck stage.The appearance of femtosecond optical frequency comb breaks the bottleneck of light source which can not have both short pulse in time domain and narrow linewidth in frequency domain,and provides a new coherent light source for laser measurement.The dual-comb measurement technology uses two optical combs to detect optical heterodyne,which gives full play to the characteristics of high resolution and high pulse rate of optical comb,and shows better comprehensive performance in measurement accuracy,dynamic range,data update rate and so on.This paper focuses on the development of a high-speed and high-precision dualoptical comb ranging system with stable time-frequency characteristics as the main line to expand the speed measurement application of the system.In this paper,a tunable electro-optic comb with simple structure and stable output is built,and then a hybrid asymmetric dual-comb ranging scheme is proposed based on this light source,which solves the problem of mutual restriction between non-ambiguity range(NAR)and data update rate.Finally,the absolute distance measurement with μ m accuracy is realized in a large range,in which NAR is 1.5 km and data update rate is 500 k Hz.Its advantages include interruptible measurement,high accuracy,wide dynamic range,fast data update rate and so on.Aiming at the high-speed target measurement,the system realizes the laboratory verification of the target velocity measurement accuracy of mm/s by means of double optical comb beat frequency detection,combined with the Doppler frequency shift velocity measurement principle.This research is ultimately helpful to form an integrated and multi-functional laser measurement system with the optical comb as the central light source.The specific studies are as follows:1.In terms of the system light source,based on the Mach-Zehnder modulation scheme,we use a single-intensity modulator to generate the optical frequency comb(OFC),further broaden the output spectrum by increasing the nonlinear effect,and verify the high coherence of the spectrum from 1545 nm to 1555 nm.The picosecond output pulse width is further compressed to femtosecond by single-mode optical fiber,and the feedforward phase-locked technique is used to compensate the noise optimization system.Finally,an electro-optic comb with high coherence,narrow pulse width,and low noise was obtained as the light source.in addition,it has the characteristics of simple structure and GHz tunability2.Based on the physical idea of "coarse tracking,fine compensation",this paper proposes a hybrid asymmetric DCR scheme,which introduces the method and experimental device in detail,analyzes the experimental results of asynchronous TOF and asymmetric DCR,compared with the reference interferometer,the system achieves1μm distance measurement consistency at short distance,and micron-level ranging consistency in long distance(km),which solves the problem that the traditional ranging method NAR and data update rate are mutually constrained and can only measure relative displacement without interruption.In the experiment,the NAR was 1.5 km and the data update rate was 500 k Hz.3.Based on the electro-optic dual frequency combs ranging system,the speed measurement experiment is further expanded,and the rapid optical asynchronous sampling and high-precision optical field frequency measurement are realized through the noise-immune dual-optical comb frequency detection method,and the physical information of the target moving target is captured with a high data update rate,at the same time,we combined with the Doppler speed measurement principle,the speed measurement accuracy of mm/s is achieved.This experiment verifies the feasibility of the integrated technology of speed measurement and distance measurement based on optical combs.