도파로 어레이 격자를 이용한 광섬유 브래그 스트레인 센서의 반사파장 신호 복원 기술

서준규,김경조,오민철,이상민,김영제,김명현,Seo, Jun-Kyu,Kim, Kyung-Jo,Oh, Min-Cheol,Lee, Sang-Min,Kim, Young-Jae,Kim, Myung-Hyun 한국광학회 2008 한국광학회지 Vol.19 No.1

광섬유 브래그 격자(fiber Bragg grating: FBG)를 이용한 스트레인 센서는 출력 값으로 브래그 반사 파장의 변화를 제공하게 된다. 본 논문에서는 브래그 격자 스트레인 센서에서 출력되는 빛을 도파로 어레이 격자(arrayed waveguide grating: AWG)에 입력시켜서 파장의 변화를 측정하는 방법을 제안한다. FBG에 스트레인이 가해지게 되면 브래그 반사 파장이 이동하게 되어 AWG를 지나서 출력되는 채널별 광 파워가 변하게 되며, 이 값들의 조합으로 구해지는 centroid 값을 계산하면 브래그 반사 파장과 인가된 스트레인 값을 얻을 수 있다. 브래그 격자의 반사 스펙트럼의 대역폭이 centroid 값에 미치는 영향을 고려하여 3-dB 대역폭이 5.4 nm인 chirped FBG를 사용하였으며, 저항 측정방식의 기존 스트레인 센서와 비교하여 오차범위가 2% 이내인 결과를 확인 하였다. FBG 센서를 외팔보에 부착하여 진동에 따른 스트레인 값을 실시간으로 측정한 결과 진동 주파수 17.8 Hz, damping 시상수 0.96 초를 얻을 수 있었다. Fiber-optic strain sensors based on Bragg reflection gratings produce the change of reflection spectrum when an external stress is applied on the sensor. To measure the Bragg reflection wavelength in high speed, an arrayed waveguide grating device is incorporated in this work. By monitoring the output power from each channel of the AWG, the peak wavelength corresponding to the applied strain could be obtained. To enhance the accuracy of the AWG wavelength interrogation system, a chirped fiber Bragg grating with a 3-dB bandwith of 5.4 nm is utilized. The high-speed response of the proposed system is demonstrated by measuring a fast varying strain produced by the damped oscillation of a cantilever. An oscillation frequency of 17.8 Hz and a damping time constant of 0.96 second are obtained in this measurement.

Health monitoring of carbon fiber-reinforced polymer composites in γ-radiation environment using embedded fiber Bragg grating sensors

Zhong Jing,Chen Feida,Rui Yuehao,Li Yong,Tang Xiaobin 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.8

Fiber-reinforced polymer (FRP) composites are considered suitable candidates for structural materials of spacecrafts due to their excellent properties of high strength, light weight, and corrosion resistance. An online health monitoring method for FRP composites must be applied to space structures. However, the application of existing health monitoring methods to space structures is limited due to the harsh space environment. Here, carbon fiber-reinforced polymer (CFRP) composites embedded with fiber Bragg grating (FBG) sensors were prepared to explore the feasibility of strain monitoring using embedded FBG sensors in g-radiation environment. The analysis of the influence of radiation on the strain monitoring demonstrated that the embedded FBG can be successfully applied to the health monitoring of FRP composites in radiation environment.

Simulation and Investigation of Humidity Sensor based on Fiber Grating Fabry-Perot

Xiong Yanling,Liang Huan,Ren Naikui,Han Junsheng,Wu Mingze 보안공학연구지원센터 2015 International Journal of Hybrid Information Techno Vol.8 No.6

In this article we have discussed the relative humidity sensor based on fiber grating Fabry-Perot (FBG-FP) coated with polyimide (PI) as a moisture sensitive film in theory. The moisture expansion coefficient of PI film as moisture strain on the FBG-FP sensor, which will result the change of the fiber core effective refractive index, the length of the F-P cavity and the period and effective refractive index of FBG. For that reason, the interference fringes of the reflection spectrum will be changed also. The shift of peak wavelength of the spectrum is traced by the simulation of Matlab. We discuss three situations: the coating on the FBG, FP cavity and the both, and regardless of the temperature changes, the simulation results show that the RH sensitivity can reach to 3.77pm/%RH, 2.12 pm/%RH, 4.05 pm/%RH, respectively.

광섬유 열 수축 슬리브를 활용한 FBG 굽힘 센서 개발

황성준(Sung Jun Hwang),김태희(Tae-Hee Kim),김대현(Dae-Hyun Kim) 한국비파괴검사학회 2020 한국비파괴검사학회지 Vol.40 No.4

단일 FBG 센서를 대신해 세 가닥의 FBG센서 광섬유 라인의 기하학적 조합을 통해 새로운 형태의 광섬유 굽힘 센서를 제안하였다. 그러나 새롭게 제안된 광섬유 굽힘 센서의 성능을 확보하기 위해서는 세 가닥의 FBG 센서 광섬유 라인을 원주 방향을 따라 서로 120도 간격으로 위치시켜야만 한다. 이러한 기하학적 구조를 만들기 위해 기존에는 섬세한 수작업을 통한 센서의 제작이 이뤄졌으나 오차 발생의 가능성이 높아 제작성이 매우 떨어진다. 따라서 본 논문에서는 기존 제작 방법의 어려움을 해결하고자 열 수축 슬리브를 이용한 새로운 제작 방법을 제안하였다. 또한 새롭게 제안한 열 수축 슬리브를 이용한 굽힘 센서와 기존의 방식으로 제작한 굽힘 센서를 각각 제작하고 두 가지 형태의 광섬유 굽힘 센서의 성능 분석을 비교하기 위해 외팔보 굽힘 실험을 수행하였다. 실험결과, 새롭게 제안한 열 수축 슬리브를 이용한 굽힘 센서의 성능이 보다 안정적임을 확인하였다. Instead of a single fiber Bragg grating (FBG) sensor, a new type of optical-fiber bending sensor was proposed through the geometrical combination of three strands of optical fiber lines of a fiber Bragg grating (FBG) sensor. The three strands of the FBG sensor optical fiber lines must be positioned at 120° intervals from one another in the circumferential direction to improve the performance of the proposed optical-fiber bending sensor. The sensor was manufactured through delicate manual work to fabricate the geometrical structure; however, the fabrication was very difficult because the possibility of error was high. Therefore, in this study, a new manufacturing method using a heat-shrink sleeve was developed to solve the problems of the conventional manufacturing method. In addition, a bending sensor was fabricated using a heat-shrink sleeve and a bending sensor manufactured based on the conventional method. Cantilever bending experimental tests were performed to compare the performance of the two types of optical-fiber bending sensors. It was confirmed that the performance of the bending sensor using the proposed heat-shrink sleeve was more stable.

변형과 온도의 동시 측정을 위한 삼중 광섬유격자 센서

윤지애,윤재순,백세종,임기건 한국물리학회 2011 새물리 Vol.61 No.9

변형과 온도를 동시에 측정하기 위하여 단일 광섬유격자와광섬유격자쌍으로 구성된 삼중 광섬유격자 센서를 제안하였다. 광섬유격자쌍은 두 개의 동일한 격자로 구성되어 두 격자의 간섭효과에의해 작은 파장 폭을 갖는 피크들로 구성되는 스펙트럼 특성을 가졌다. 이러한 특성을 이용하여 단일 격자보다 잡음에 강하고, 높은 정확도의파장 변화 측정이 가능하다. 또한, 두 격자 사이의 간격 변화에 따른스펙트럼 패턴의 주파수 변화를 활용하여 센서에 다중화 기능을 부여할수 있다. 전달행렬법(Transfer Matrix Method, TMM)을 이용하여 삼중광섬유격자 센서의 반사 스펙트럼을 계산하고, 변형과 온도에 따라선형적으로 이동하는 스펙트럼 특성을 컴퓨터 모의실험을 통하여확인하였다. 또한 전달행렬법과 Nelder-Mead Simplex 알고리즘을 사용한최적화 프로그램을 통하여 온도와 변형을 찾는 디모듈레이션을수행하였다. 위상마스크 방법을 이용하여 삼중 광섬유격자 센서를제작하여, 온도와 변형에 따른 스펙트럼 특성을 확인하였다. 본실험에서의 광섬유격자 쌍의 온도 민감도는 8pm/℃이며,단일격자의 변형 민감도는 1.2 pm/με 임을 보였다. 이론적계산오차는 온도는 0.003℃이하, 변형에 대해 0.2με에서 결정할 수 있었고 실험적 오차는 온도는 1.85℃이하, 변형에 대해 31.35με로 결정할 수있었다. We propose a triple fiber Bragg grating (FBG) sensor for simultaneous measurement of strain and temperature. The sensor consists of a single FBG and a twin FBG. The twin FBG consists of two identical gratings separated by a short distance. The reflectance spectrum has a multi-peaked structure due to the interference of the beams reflected from the two gratings. By employing a twin FBG, we can obtain high-accuracy in the measurement of wavelength shift. A computer simulation of the reflectance spectrum of the triple FBG sensor was performed. The Bragg wavelength changed linearly with both strain and temperature. The transfer matrix method (TMM) and the Nelder-Mead simplex algorithms were utilized in the optimization procedure. We fabricated a triple FBG sensor by using the phase mask method to confirm its feasibility for simultaneously measuring the strain and the temperature. The sensitivities for the temperature and the strain were experimentally measured to be 8pm/℃ and 1.2pm/με,respectively. The measurement accuracies were better than 10^(-3)℃ and 0.2με, respectively. The temperature and the strain were simultaneously measured within errors of 1.85℃ and 31.35με, respectively, by using the optimization procedure.

광섬유격자센서와 회전광학커플러를 사용한 새로운 회전축의 토크 측정방법

이종민(Lee, Jong-Min),황요하(Hwang, Yo-Ha) 한국소음진동공학회 2007 한국소음진동공학회 논문집 Vol.17 No.12

Torque of a rotating shaft has been mostly measured by strain gages combined with either a slip ring or telemetry. However, these methods have severe inherent problems like low S/N ratio, high cost, limited number of channels and difficult installation. In this paper, a new method using FBG(fiber bragg grating) sensors and a rotary optical coupler for online non-contact torque monitoring is suggested. FBG sensor can measure both strain and temperature, and has much batter characteristics than those of a strain gage. A rotary optical coupler is a optical connecting device between a rotating shaft and stationary side without any physical contact. It has been devised for transmitting light between a rotating optical fiber and a stationary optical fiber. The proposed method uses this rotary optical coupler to connect FBG sensors on the rotating shaft to instruments at stationary side. And a reference FBG sensor is also applied to compensate the insertion loss change of the rotary optical coupler due to rotation. Three FBG sensors have been fabricated in a single optical fiber. Two FBG sensors are attached on the shaft surface to measure torque and one sensor is installed at the shaft center to compensate the insertion loss change. The torque of a rotating shaft has been successfully measured by the suggested method proving its superior performance potential.

광섬유 브래그 격자 센서를 이용한 에폭시 수지의 경화도 모니터링

이진혁(Jin-Hyuk Lee),김대현(Dae-Hyun Kim) 한국비파괴검사학회 2016 한국비파괴검사학회지 Vol.36 No.3

에폭시 수지는 여러 산업분야에서 다양한 구조물의 접합과 제조에 사용된다. 구조물의 안전성과 접합재료의 최적 성능 확보를 위해서는 에폭시 수지의 경화 과정 모니터링 기반의 공정 제어가 요구된다. 광섬유 센서는 실과 같은 형태적 특징으로 인해 에폭시 수지의 경화 모니터링에 적합한 센서이다. 본 연구에서는 광섬유 브래그 격자 센서(fiber Bragg grating, FBG)를 이용하여 에폭시 수지의 경화 모니터링 연구를 수행하였다. 실제 실험을 통해, FBG를 기반으로 에폭시 수지의 경화과정에서 에폭시의 부피 수축에 의해 센서에 가해지는 변형률을 측정하고 온도의 변화에 의한 신호 변화를 보정하여 경화과정에서 발생하는 변형률의 정확한 모니터링이 가능함을 확인하였다. 추가적으로, 두 가지 에폭시 수지의 경화도 과정을 비교 분석하여 에폭시 종류에 따른 경화과정의 차이를 확인하였다. 결론적으로 FBG 센서가 에폭시 수지의 경화도 모니터링에 유용하다는 점을 확인하였다. In several industrial fields, epoxy resin is widely used as an adhesive for co-curing and manufacturing various structures. Controlling the manufacturing process is required for ensuring robust bonding performance and the stability of the structures. A fiber optic sensor is suitable for the cure monitoring of epoxy resin owing to the thready shape of the sensor. In this paper, a fiber Bragg grating (FBG) sensor was applied for the cure monitoring of epoxy resin. Based on the experimental results, it was demonstrated that the FBG sensor can monitor the status of epoxy resin curing by measuring the strain caused by volume shrinkage and considering the compensation of temperature. In addition, two types of epoxy resin were used for the cure-monitoring; moreover, when compared to each other, it was found that the two types of epoxy had different cure-processes in terms of the change of strain during the curing. Therefore, the study proved that the FBG sensor is very profitable for the cure-monitoring of epoxy resin.

FBG 센서를 활용한 온도와 스트레인 변화 모니터링

고기한,박영,조용현,정호성,조용석,최원석,Ko, Ki-Han,Park, Young,Cho, Yong-Hyeon,Jung, Ho-Sung,Cho, Yong-Suk,Choi, Won-Seok 한국전기전자재료학회 2009 전기전자재료학회논문지 Vol.22 No.3

This paper reports on measurement method for the fiber optic strain monitoring of overhead contact line systems of trains, We used FBG (Fiber Bragg Grating) sensors to measure the strain variation of overhead contact line. FBG sensors can sensitively measure the variation of strain and! or temperature by the shift wavelength of reflected wave according to the lattice variation during the measurement. FBG sensor were attached on the contact line and connected to the monitoring system with optical fibers. The monitering system with FBG sensors showed very good sensitivity to measuring strain variation and this system could be applied to the overhead contact line of KTX (Korea Train eXpress).

이중 FBG 광섬유센서를 이용한 구조물 가속도 및 기울기 측정 장치에 관한 연구

이금석,안수홍,손수덕,이승재,Lee, Geum-Suk,Ahn, Soo-Hong,Shon, Su-Deok,Lee, Seung-Jae 한국공간구조학회 2016 한국공간구조학회지 Vol.16 No.1

In this study, an acceleration sensor that has optical fibers to measure the inclination and acceleration of a structure through contradictory changes in two-component FBG sensors was examined. The proposed method was to ensure precise measurement through the unification of the deformation rate sensor and the angular displacement sensor. A high sensitivity three-axis accelerometer was designed and prepared using this method. To verify the accuracy of the accelerometer, the change in wavelength according to temperature and tension was tested. Then, the change in wavelength of the prepared accelerometer according to the sensor angle, and that of the sensor according to the change in ambient temperature were measured. According to the test results on the FBG-based vibration sensor that was developed using a high-speed vibrator, the range in measurement was 0.7 g or more, wavelength sensitivity, 2150 pm/g or more, and the change in wavelength change, $9.5pm/^{\circ}C$.

광섬유 브래그 격자 센서를 이용한 보 구조물의 3차원 형상 추정

이진혁(Jin-Hyuk Lee),김헌영(Heon-Young Kim),김대현(Dae-Hyun Kim) 대한기계학회 2015 大韓機械學會論文集A Vol.39 No.3

교량이나 배관과 같이 긴 길이의 구조물은 처짐 및 변형이 발생하기 쉽다. 이러한 구조물의 건전성 감시를 위해서는 국부적인 물리량 측정뿐만 아니라 전체의 형상 감시가 필요하다. 광섬유 브래그 격자(Fiber Bragg Grating; FBG) 센서는 광섬유에 다수의 센서 적용이 가능하여 대형 구조물 감시에 효과적이다. 본 연구에서는 FBG를 이용하여 구조물의 다점에서 변형률을 측정하고, 이를 바탕으로 구조물 전체의 형상 추정을 위한 연구를 수행하였다. 구조물의 정확한 감시가 가능하도록 3차원의 형상 추정을 연구하고 실험적 검증을 수행하였다. 실험 결과 구조물의 변형에 따른 형상 변화의 추정이 가능함을 확인하였고, 추가로 특정 위치에서의 처짐량을 실제 마이크로미터로 측정한 값과 예측된 값을 비교하여 검증하였다. Deflection and deformation occur easily in structures with long length, such as bridges and pipelines. Shape monitoring is required for ensuring their structural health. A fiber Bragg grating (FBG) sensor can be used for monitoring a large-scale structure because of its advantage of multiplexing. In this study, FBG sensors were used for monitoring a composite beam structure, and its strains were measured at multiple points. Thereafter, a shape estimation technique based on the strains was studied. Particularly, a three-dimensional shape estimation technique was proposed for accurate structural health monitoring. A simple experiment was conducted to verify the performance of the shape estimation technique. The result revealed that the estimated shape of the composite beam structure was in agreement with the actual shape obtained after the deformation of the specimen. Additionally, the deflection at a specific point was verified by comparing the estimated and actual deformations measured using a micrometer.