Performance evaluation of a mandrel type fiber optic underwater acoustic sensor using finite element analysis and experiments

Min-Seop Sim; Chang-Taek Oh; Min-Seo Lee; Seung-Jin Lee; Hong-Woo Yoon; Kook-Jin Kang

doi:10.7776/ASK.2026.45.5.485

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2026 Vol.45, Issue 5 Preview Page Next Page

Performance evaluation of a mandrel type fiber optic underwater acoustic sensor using finite element analysis and experiments 유한요소해석 및 실험을 통한 맨드릴형 광섬유 수중음향센서의 성능 평가

30 September 2026. pp. 485-498

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Abstract

This paper systematically evaluates the Receiving Voltage Sensitivity (RVS) and Noise Equivalent Pressure (NEP) of an underwater acoustic sensor integrating a mandrel type fiber optic sensor with a commercial Distributed Acoustic Sensing (DAS) system. We used the Finite Element Analysis (FEA) and the experiments for the performance evaluation. FEA results, the reference model of a mandrel type fiber optic sensor (MC-Nylon, inner radius 17 mm, 100 turns) yielded a flat sensitivity of approximately –152 dB re rad/μPa over 100 Hz to 4 kHz. Increasing the mandrel thickness from 2 mm to 10 mm results in a sensitivity loss of approximately 15.4 dB, while increasing the number of winding turns from 50 to 200 improves sensitivity by approximately 11.4 dB, in good agreement with the theory that phase variation is proportional to the effective fiber length. In the material comparison, flexible materials show more than 6 dB higher sensitivity than MC-Nylon, however, sensitivity converges to approximately –141 dB re rad/μPa when the elastic modulus falls below 100 MPa. Underwater test results show that the 20 m prototype yields –151.86 dB re rad/μPa and the 25 m prototype yields –149.22 dB re rad/μPa at 2 kHz, showing a measured sensitivity difference of 2.64 dB, which is in reasonable agreement with the theoretical prediction of 1.94 dB. The measured NEP ranged from approximately 42 dB to 57 dB re μPa/√Hz over the 1 kHz to 4 kHz, exceeding the Wenz curve Sea State 0, Sea State 1 baselines at all measured frequencies. DAS parameter analysis experimentally demonstrates that increasing the Gauge Length (GL) is the most effective approach for NEP reduction. Potential directions for performance improvement through the adoption of Ultra Weak Fiber Bragg Grating (UWFBG) and optimized mandrel structures are proposed.

Keywords

Finite Element Analysis (FEA)

Mandrel type fiber optic underwater acoustic sensor

Receiving Voltage Sensitivity (RVS)

Noise Equivalent Pressure (NEP)

본 논문에서는 상용 Distributed Acoustic Sensing(DAS) 시스템과 맨드릴형 광섬유 센서를 결합한 수중음향센서에 대해 유한요소해석(Finite Element Analysis, FEA)과 실험을 통하여 수신감도(Receiving Voltage Sensitivity, RVS) 및 등가 잡음 음압(Noise Equivalent Pressure, NEP) 성능을 체계적으로 평가하였다. 유한요소해석 결과, MC-Nylon 기준 모델(내경 17 mm, 100권선)의 수신감도는 100 Hz ~ 4 kHz 대역에서 약 –152 dB re rad/μPa로 산출되었다. 맨드릴 두께 2 mm 대비 10 mm에서 약 15.4 dB 의 감도 손실이 확인되었고, 권선 횟수를 50회에서 200회로 증가시킬 때 약 11.4 dB의 향상이 관측되어 위상 변화량이 광섬유 유효 길이에 비례한다는 이론과 일치하였다. 재질 비교에서는 유연 재료가 MC-Nylon 대비 약 6 dB 이상 높은 감도를 나타냈으나, 탄성 계수 100 MPa 이하에서 감도가 –141 dB re rad/μPa수준으로 수렴하였다. 수중 시험 결과, 광섬유 길이 20 m 시제품은 2 kHz에서 –151.86 dB re rad/μPa, 25 m 시제품은 –149.22 dB re rad/uPa를 나타내어 두 시제품 간 약 2.64 dB의 감도 차이가 측정되었으며, 이는 이론 예측(1.94 dB)과 유사한 경향을 확인하였다. 등가 잡음 음압은 1 kHz ~ 4 kHz 대역에서 약 42 dB re μPa/√Hz ~ 57 dB re μPa/√Hz로 산출되어 Wenz 곡선 기반 Sea State 0, Sea Sate 1 기준선을 전 주파수에서 상회하였다. DAS 파라미터 분석에서는 Gauge Length(GL) 증가가 등가 잡음 음압 저감에 가장 효과적임을 실험적으로 증명하였으며, 향후 Ultra Weak Fiber Bragg Grating(UWFBG) 적용 및 맨드릴 구조 최적화를 통한 성능 개선 방향을 제시하였다.

키워드

유한요소해석(Finite Element Analysis, FEA)

맨드릴형 광섬유 수중음향센서

수신감도(Receiving Voltage Sensitivity, RVS)

등가 잡음 음압(Noise Equivalent Pressure, NEP)

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Information

Publisher :The Acoustical Society of Korea
Publisher(Ko) :한국음향학회
Journal Title :The Journal of the Acoustical Society of Korea
Journal Title(Ko) :한국음향학회지
Volume : 45
No :5
Pages :485-498
Received Date : 2026-08-03
Revised Date : 2026-09-01
Accepted Date : 2026-09-11
DOI :https://doi.org/10.7776/ASK.2026.45.5.485

The Journal of the Acoustical Society of KoreaISSN:1225-4428(Print) 2287-3775(Online)한국음향학회

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