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Non-contact Detection of Ultrasonic Waves Using Fiber Optic Sagnac Interferometer

광섬유 Sagnac 간섭계를 이용한 초음파의 비접촉식 감지

  • Lee, Jeong-Ju (Dept. of Mechanical Engineering, Korea Advanced Institute of Science and Technology) ;
  • Jang, Tae-Seong (Dept. of Mechanical Engineering, Korea Advanced Institute of Science and Technology) ;
  • Lee, Seung-Seok (Measurement Group, Korea Reserch Institute of Standards and Science) ;
  • Kim, Yeong-Gil (Measurement Group, Korea Reserch Institute of Standards and Science) ;
  • Gwon, Il-Beom (Measurement Group, Korea Reserch Institute of Standards and Science) ;
  • Lee, Wang-Ju
  • 이정주 (한국과학기술원 기계공학과) ;
  • 장태성 (한국과학기술원 기계공학과) ;
  • 이승석 (한국표준과학연구원 비파괴계측그룹) ;
  • 김영길 (한국표준과학연구원 비파괴계측그룹) ;
  • 권일범 (한국표준과학연구원 비파괴계측그룹) ;
  • 이왕주
  • Published : 2001.09.01

Abstract

This paper describes a fiber optic sensor suitable for non-contact detection of ultrasonic waves. This sensor is based on a fiber optic Sagnac interferometer. Quadrature phase bias between two interfering laser beams in Sagnac loop is introduced by a polarization controller. A stable quadrature phase bias can be confirmed by observing the interferometer output versus phase bias. This method eliminates a digital signal processing for detection of ultrasonic waves using Sagnac interferometer. Interference intensity is affected by the frequency of ultrasonic waves and the time delay of Sagnac loop. Collimator is attached to the end of the probing fiber to focus the light beam onto the specimen surface and to collect the reflected light back into the fiber probe. Ultrasonic waves produced by conventional ultrasonic transducers are detected. This fiber optic sensor based on Sagnac interferometer is very effective for detection of small displacement with high frequency such as ultrasonic waves used in conventional non-destructive testing.

Keywords

References

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