Research And Application Of All-fiber VISAR Technology

With the development of laser technology, laser interferometer velocimetry technology has made a revolutionary breakthrough to traditional speed test. Since the 70’s of last century, laser interferometer velocimetry technology has undergone VISAR Interferometer, fabry-perot interferometer, white-light interferometer, all-fiber VISAR in 40 years. Today, all-fiber VISAR technology has become the mainstream of laser interferometer velocimetry technology as its compact structure, low coherence of the laser, debugging simpler, wide measuring range and high precision.For the needs of transient velocity measurement, the main research of the article is free-surface speed testing application of the shock-wave. The software and hardware of all-fiber VISAR system which was successfully used in practice was considered. The innovations of the article:1. Introducing 3X3 coupler and DC monitoring terminal in the optical structure which were used to eliminate the effect of optical energy changes and provide external trigger signals for digital oscilloscope to get interference fringes.2. Designed lens groups with anti-deflection ability and high efficiency of reflected rays to demands for test environments:central wavelength is 1310nm, aperture is 14mm, focal length is 26mm, measuring range is 50mm-2000mm and theoretical efficiency of reflected rays is above 70%.3. In the signal processing of interference fringes, solve the effect of disturbance signals from light intensity and the method was proved by simulation.4. Validate the accuracy and wide range frequency characteristics of the all-fiber VISAR system in the experiment of vibro-bench acceleration measurement, compared with standard accelerometer.5. Achieved free-surface speed testing application of the shock wave with all-fiber VISAR system, and the experiment realized long time measurement(200μs) in strong disturbance, which was almost no relevant reports in or abroad.6. Applied FVISAR system in high velocity measurement. Because of the limited of digital oscilloscope and the lower efficiency of reflect rays, some of the stripes lost, which impact the accuracy of test results, but the experiment still got the process of flyer flight.The structure of the article:Chapter 1:introduced the advancement of laser interferometer velocimetry technique compared with several methods of common speed test. Reviewed the development history of laser interferometer velocimetry technique in 40 years and state the current situations in and abroad. Representative introduced structures and principles of Michelson Interferometer, VISAR Interferometer and white-light Interferometer, especially on issues of system bandwidth and coherence of laser.Chapter 2:the experimental optical path of all-fiber VISAR was designed on the basis of L.LEVIN’s, added with DC monitoring terminal, two 3×3 couplers and optical transceiver device. The improved optical path is stability and commonality. The article discussed the components involved in the optical path.Chapter 3:the emphasis of the software process was the analysis method in harsh environments. Mainly used solutions were light intensity software to zero, eliminating the interference of reflected rays; high-order filter and signal normalization to extract more stable interference fringes; and adapted phase restore technology to calculate the measured velocity.Chapter 4:the chapter has recorded four experiments:the vibration of vibro-bench test, acceleration-calibration test, shock-wave speed test and flyer speed test. Experiments provided important reference value to further research of all-fiber velocity sensorsChapter 5:summary and prospect.