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Acoustic Sensitivity Analysis of a Ring-type Probe Based on a Fiber-optic Sagnac Interferometric Sensor

광섬유 사냑 간섭형 센서에 기반한 링형 탐촉자의 수중 음향 민감도 해석

  • Lee, Yeon-Woo (Department of Measurement Science, University of Science and Technology) ;
  • Kwon, Hyu-Sang (Center for Optical Metrology, Korea Research Institute of Standards and Science) ;
  • Kwon, Il-Bum (Center for Safety Measurement, Korea Research Institute of Standards and Science)
  • 이연우 (과학기술연합대학원대학교 측정과학과) ;
  • 권휴상 (한국표준과학연구원 광학표준센터) ;
  • 권일범 (한국표준과학연구원 안전측정센터)
  • Received : 2019.11.20
  • Accepted : 2019.12.19
  • Published : 2020.02.25

Abstract

To measure underwater acoustics using a fiber-optic Sagnac interferometric sensor, the sensitivities of ring-type probes are investigated by theoretical and experimental studies. A ring-type probe was fabricated by packaging a single-mode fiber wound around an acrylate cylinder of diameter 5 cm with epoxy bond. The probes were prepared as A-type, which was packaged with 46.84 m of sensing optical fiber, and B-type, which was packaged with 112.22 m of sensing fiber. The underwater acoustic test was performed at frequencies of 50, 70, and 90 kHz, and over a range of acoustic pressure of 20-100 Pa, to study the sensitivity. A commercial acoustic generator was located 1 m from the acoustic sensor, such as the ring-type probe or a commercial acoustic sensor. From the experimental test, the acoustic sensitivity of the ring-type probe had different values due to acoustic frequencies, unlike the theoretical prediction. Therefore, the experimental sensitivities were averaged for comparison to the theoretical values. These averaged sensitivities are 25.48 × 10-5 rad/Pa for the A-type probe and 60.79 × 10-5 rad/Pa for the B-type probe. The correction coefficient of Young's modulus c was determined to be 0.35.

광섬유 사냑 간섭형 센서를 이용해 수중 음향을 측정하기 위하여 링형 탐촉자를 적용하는 경우 민감도를 이론과 실험을 통하여 조사한다. 링형 탐촉자는 단일 모드 광섬유를 지름 5 cm의 링형으로 감아서 접착제로 패키징하였다. 링형 탐촉자는 감지 광섬유의 길이를 46.84 m로 하여 제작한 A형 탐촉자와 감지 광섬유의 길이를 112.22 m로 한 B형 탐촉자를 준비하였다. 수중 음향 시험은 상용 음향 발생기와 1 m 떨어진 거리에서 링형 탐촉자를 사용하여 50, 70, 90 kHz의 주파수에 대하여 20~100 Pa의 음향 압력 범위에서 음향 민감도를 조사하는 실험을 수행하였다. 실험 결과, 링형 탐촉자는 주파수에 대하여 다른 민감도를 나타내었으며, 이론과 비교하기 위하여 평균값을 구하였다. 세 주파수에 대한 평균 민감도는 A 탐촉자와 B 탐촉자에 대하여 각각 25.48 × 10-5, 60.79 × 10-5 rad/Pa으로 측정되었으며, 이로부터 영률 보정 계수 c값을 0.35로 결정할 수 있었다.

Keywords

References

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