• Title, Summary, Keyword: Intensity-based Optical Fiber Sensors

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Monitoring of Fatigue Damage of Composite Laminates Using Embedded Intensity-Based Optical Fiber Sensors (광강도형 광섬유 센서를 이용한 복합재 적충판의 피로손상 감시)

  • 이동춘;이정주;서대철
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.124-127
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    • 2000
  • In this study, a technique for monitoring of fatigue damage of composite laminates by measuring the stiffness change using embedded intensity-based optical fiber sensors was investigated. Firstly, the underlying measurement principle and structure of intensity-based sensors and then a simple stiffness conversion process was explained. The monitoring technique was evaluated by fatigue tests of composite laminates with an embedded intensity-based sensor. From the test results, the response of the intensity-based sensor showed good correlation with that of surface mounted extensometer. Therefore, it can be concluded that the intensity-based sensors have good potential for the monitoring of fatigue damage of composite structures under fatigue loading. In addition, it could be confirmed that the intensity-based sensors have higher resistance to fatigue than the commercial electrical strain gauge.

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Analytic Formulation of Transmission Light Intensity of Hole Blockers in Intensity-based Polymer Optical Fiber Sensors

  • Kwon, Il-Bum;Kim, Chi-Yeop;Shim, Chan-Wook;Hwang, Du-Sun;Chung, Yung-Joo
    • Journal of Sensor Science and Technology
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    • v.20 no.4
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    • pp.221-225
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    • 2011
  • Intensity-based optical fiber sensors are devised using a blocker which is located between two polymer optical fibers(POFs), one fiber is light-in and the other is light-out. This blocker is moved by an external displacement. Therefore, finding a general formulation of the relation between this displacement and transmission light intensity of various blockers is important to help develop intensity-based optical fiber sensors. In this paper, we consider blockers with arbitrary shapes from circular holes to inclined angled blockers. The transmission light intensities of such blockers should be determined by this generalized equation. In order to verify this equation, the calculated intensities of the blockers are compared with the values acquired from experiment. In the comparison, it is shown that the analytic equation can give the exact values of the transmitted light intensities for the assorted blockers. The range of the displacement measurement is also shown to be about 6 times of the radius of the hole in the case of a 9 degree inclined angle blocker.

Fatigue Damage Detection and Vibration Sensing Using Intensity-Based Optical Fiber Sensors (광강도형 광섬유센서를 이용한 피로손상 및 진동감지)

  • 양유창;전호찬;한경섭
    • Composites Research
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    • v.13 no.1
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    • pp.89-97
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    • 2000
  • Fatigue damage detection and vibration sensing for a laminated composites and impact location detection for a steel beam have been carried out using optical fiber sensor. Intensity based optical fiber sensor is constructed by placing two cleaved fiber end in a hollow glass tube, and multiple reflection within the cavity is considered. Fatigue signals are measured by embedded optical fiber, surface mounted optical fiber sensor and strain gage simultaneously. For vibration sensing, optical fiber sensor is mounted on the carbon fiber composite beam and its response to free vibration and forced vibration is investigated. In impact location detection, two optical fiber sensors are used and the information obtained from two sensors is arrival time delay of vibration caused by impact. Impact location can be calculated from this time delay. The obtained results show that the intensity based optical fiber sensor provide reliable data during long-term fatigue loading, unlike strain gage which deteriorate during the early part of the fatigue test. Optical fiber sensor signals coincide with gap sensor in vibration sensing. The precise locations of impact can be detected within 4.1% error limit.

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Effect on the structural integrity and fatigue damage monitoring of smart composite structures with embedded intensity based optical fiber sensors (삽입된 광강도형 광섬유센서가 지능형 복합재 구조물의 건전성에 미치는 영향 및 피로손상 감시)

  • Lee, Dong-Chun;Lee, Jung-Ju;Seo, Dae-Cheol;Huh, Jeung-Soo
    • Journal of Sensor Science and Technology
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    • v.10 no.1
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    • pp.42-51
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    • 2001
  • In this study, the effects of embedded optical fibers on the static properties under tensile load and dynamic properties under fatigue load of composite laminates were investigated by experimental tests and finite element analysis. Based on the results, it can be concluded that the embedded optical fiber sensors do not have significant effects on the structural integrity of the smart composite structures except when the sensors are embedded perpendicular to the adjacent reinforcing fibers under fatigue loading. An intensity-based optical fiber sensor was embedded in the crossply composite laminates to monitor the fatigue damage by detecting the stiffness changes of the laminates. The result of this experiment has shown that the intensity-based optical fiber sensor has large potential to monitor the fatigue damage of composite structures by detecting the stiffness changes of the structures with simple and inexpensive instruments and without complex post-processing of measured signals. In addition, the optical fiber sensor showed good resistance to fatigue loading and wide sensing ranges of stiffness.

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Fabrication of Optical Fiber Gas Sensor with Polyaniline Clad

  • Lee, Yun-Su;Song, Kap-Duk;Joo, Byung-Su;Lee, Sang-Mun;Choi, Nak-Jin;Lee, Duk-Dong;Huh, Jeung-Soo
    • Journal of Sensor Science and Technology
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    • v.13 no.2
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    • pp.96-100
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    • 2004
  • Optical fiber sensors have been used to detect small amounts of chemical species. In this work, a new thin polymer-clad fiber sensor is developed. Polyaniline is chemically synthesized and thin clad layers of the polymer are easily deposited on optical fiber by dip-coating technique. The optical property of polyaniline as a sensing material is analyzed by UV-Vis-NIR. The light source is stabilized He-Ne laser at 635 nm wavelength with 1 mW power. The light power transmitted through the optical fiber is measured with a spectrophotometer. By selecting a fixed incident angle, variation of transmitted light intensity through the optical fiber can be detected as gas molecules absorbed in the polyaniline clad layer. Among the various gases, the fabricated optical fiber sensor shows good sensitivity to $NH_{3}$ gas. The optical fiber sensors was shown more improved properties than polymer based sensors which measure conductivity changes.

A study on the application of optical fiber sensors to smart composite structures (지능형 복합재 구조물에 대한 광섬유센서의 적용에 관한 연구)

  • Jang, Tae-Seong;Kim, Ho;Lee, Jung-Ju
    • Journal of Sensor Science and Technology
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    • v.5 no.6
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    • pp.15-24
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    • 1996
  • In this study, as a part of the basic study for the application of optical fiber sensors to smart composite structures, the integrity of optical fiber sensors embedded within the composite structures was examined and then the laser signal transmitted through optical fiber sensors during the deformation of host structures was investigated. Firstly, it was found that bending test could be substituted for tensile test by comparing cumulative failure distribution based on weakest link theory and introducing the correction factor. Weibull parameters were obtained through the experiments and the correction factor was found to be applied to cumulative failure distribution derived from bending test. The integrity of embedded optical fiber sensors due to the thermal effect was evaluated by the comparison of the mean tensile strengths of cured and uncured optical fibers. Secondly, relationships between stress-strain curve obtained in tensile test of composite laminate and the intensity of laser signal transmitted through embedded optical fibers were examined and the possibility of the effective damage detection using optical fiber sensors was studied.

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Development of Micro-opto-mechanical Accelerometer using Optical fiber (광섬유를 이용한 미세 광 기계식 가속도 센서의 개발)

  • Lee, Seung-Jae
    • Journal of the Korean Society of Mechanical Technology
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    • v.13 no.4
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    • pp.93-99
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    • 2011
  • This paper presents a new type of optical silicon accelerometer using deep reactive ion etching (DRIE) and micro-stereolithography technology. Optical silicon accelerometer is based on a mass suspended by four vertical beams. A vertical shutter at the end of the mass can only moves along the sensing axis in the optical path between two single-mode optical fibers. The shutter modulates intensity of light from a laser diode reaching a photo detector. With the DRIE technique for (100) silicon, it is possible to etch a vertical shutter and beam. This ensures low sensitivity to accelerations that are not along the sensing axis. The microstructure for sensor packaging and optical fiber fixing was fabricated using micro stereolithography technology. Designed sensors are two types and each resonant frequency is about 15 kHz and 5 kHz.

Multi-point detection of hydrogen using the hetero-core structured optical fiber hydrogen tip sensors and Pseudorandom Noise code correlation reflectometry

  • Hosoki, Ai;Nishiyama, Michiko;Igawa, Hirotaka;Seki, Atsushi;Watanabe, Kazuhiro
    • Journal of Power System Engineering
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    • v.19 no.3
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    • pp.11-15
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    • 2015
  • In this paper, the multi-point hydrogen detection system based on the combination of the hetero-core optical fiber SPR hydrogen tip sensor and interrogator by pseudorandom noise (PN) code correlation reflectometry has been developed. In a light intensity-based experiment with an LED operating at 850 nm, it has been presented that a transmitted loss change of 0.32dB was induced with a response time of 25 s for 4% $H_2$ in $N_2$ in the case of the 25-nm Au, 60-nm $Ta_2O_5$, and 5-nm Pd multi-layers film. The proposed sensor characteristic shows excellent reproducibility in terms of loss level and time response for the in- and out- $H_2$ action. In addition, in the experiment for multi-point hydrogen detection, all sensors show the real-time response for 4% hydrogen adding with reproducible working. As a result, the real-time multi-point hydrogen detection could be realized by means of the combination of interrogating system and hetero-core optical fiber SPR hydrogen tip sensors.

Development of submersion sensors using multi-mode fibers spliced with a fiber Bragg grating (다중모드 광섬유 융착형 침수 감지 센서 개발)

  • Sohn, Kyung-Rak;Key, Kwang-Hyun;Shim, Joon-Hwan;Cho, Seok-Je
    • Journal of Advanced Marine Engineering and Technology
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    • v.33 no.6
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    • pp.925-931
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    • 2009
  • This paper reports a preliminary experimental investigation and characterization of an optical fiber-based submersion sensor system for applications in water flooding and leakage. The sensor system comprises a multi-mode fiber spliced with fiber Bragg grating and an intensity-based interrogator. Submersion tests were conducted in water-air and Glycerin-air environments. By the refractive index of the fiber-probe surrounding materials, the reflectance and the detecting power level is determined. When the probe is dipped into the water, the optical output power dramatically decreases from -7.5dBm to -17.5dBm. But, the center of Bragg wavelength is not affected in spite of external material changes. Temporal response characteristics of the sensor system is investigated to verify the real-time reaction. When the probe is immersed into the liquid, there is no transition time.

A Study on the Tank Liquid-Level Monitoring Sensor Systems for Large Scaled Vessels (대형선박의 액체 탱크용 수위 모니터링 센서 시스템 연구)

  • Sohn, Kyung-Rak;Kim, Jin-Wook;Cho, Seok-Je;Shim, Joon-Hwan
    • Journal of Advanced Marine Engineering and Technology
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    • v.33 no.2
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    • pp.330-335
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    • 2009
  • A fiber-optic liquid level sensor based on bending cantilever beam has been proposed. A fiber Bragg grating(FBG) embedded in the cantilever beam is used to sensing elements. The basic concept is elongation and constriction of the FBG corresponding to the liquid level variation. The best FBG position on the cantilever for obtaining the high sensitivity was 4 cm from the fixing point. When the liquid level moves up and down vertically, the Bragg wavelength is linearly shifted. But, the wavelength sensitivity of the FBG installed on the upper side of cantilever was four times better than that of the FBG equipped in the lateral side due to the difference of unit strain applied to the FBG. Intensity demodulation using the low-cost edge filter is used to interrogate the Bragg wavelength through converting the wavelength signals into the optical intensity ones. Experiment results show that the electrical output is exponentially proportional to the liquid level. But, it should be overcome for applying to the ships.