• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2002년도 추계학술대회논문초록집
• /
• pp.329.1-329
• /
• 2002

To detect external vibration signals on the latticed fence structure, distributed fiber optic sensor using Sagnac interferometer was fabricated and tested. The latticed structure fabricated with dimension of 170cm in width and 180cm in height, the optical fiber, 50m in lengtn, distributed and fixed on the latticed structure. It was verified the sensitivity of the Sagnac interferometer using the PZT phase modulator. Fiber-optic external vibration signal applied to the latticed structure from 100㎐ to several ㎑. (omitted)

• 조명전기설비학회논문지
• /
• 제27권8호
• /
• pp.75-82
• /
• 2013

We propose a fiber grating sensor system for condition monitoring of large scale wind turbine blades. For the feasibility test of the proposed sensor system, a down-scaled wind turbine has been constructed and experimented. Fiber grating sensors were attached on a blade surface for distributed strain and temperature measurements. An optical rotary joint was used to transmit optical signals between the FBG sensor array and the signal processing unit. Instead of broadband light source, we used a wavelength-swept fiber laser to obtain high output power density. A spectrometer demodulation is used to alleviate the nonlinear wavelength tuning problem of the laser source. With the proposed sensor system we could measure dynamic strain and temperature profiles at multi-positions of rotating wind turbine blades.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2004년도 학술대회지
• /
• pp.876-879
• /
• 2004

The buried fiber optic cable as a distributed intrusion sensor for detecting and locating intruders along the long perimeters is proposed. Phase changes resulting from either the pressure of the intruder on the ground immediately above the buried fiber or from seismic disturbances in the vicinity are sensed by a phase-sensitive optical time-domain reflectometer. Light pulses from a Er:fiber cw laser with a narrow, <3kHz-range, spectral width and a frequency drift of < 1 MHz/min are injected into one end of the fiber, and the backscattered light from the fiber is monitored with a photodetector. Results of preliminary studies, measurement of phase changes produced by pressure and seismic disturbances in buried fiber optic cables and simulation of ${\varphi}-OTDR$ response over long fiber paths, to establish the feasibility of the concept are described. The field experiments indicate adequate phase changes, more than 1t-rad, are produced by intruders on foot and vehicle for burial depths in the 0.2 m to 1 m range in sand, clay and fine gravel soils. The simulations predict a range of 10 km with 35 m range resolution and 30 km with 90 m range resolution. This technology could in a cost-effective manner provide enhanced perimeter security.

• 한국광학회지
• /
• 제12권4호
• /
• pp.294-299
• /
• 2001

최근에 구조물의 안전 감시를 위하여 광섬유 센서를 개발하기 위한 연구가 활발하게 진행되고 있다. 따라서 본 연구에서는 구조물의 넓은 면적에 분포되어있는 변형률을 한 개의 광섬유 라인으로 측정하기 위한 광섬유 BOTDA(Brillouin Optical Time Domain Analysis) 센서를 개발하는 연구를 수행하였다. 광섬유 BOTDA 센서는 2개의 광전 변조기 (electro-optic modulator)를 사용하여 간단하게 구성하였다. 광섬유의 변형률 측정실험을 통하여 광섬유의 전체길이 4.8km중에 변형률이 가해진 10m 구간의 변형률을 200회 평균화 처리된 신호로부터 브릴루앙 주파수 천이를 측정함에 의하여 정확하게 측정할 수 있음을 보였다. 또한 삼성전자의 단일모드 광섬유의 경우 변형률 측정 실험을 통하여 변형률 감지도가 4.81 MHz/0.01%임을 알 수 있었다.

• 한국정밀공학회지
• /
• 제21권5호
• /
• pp.142-148
• /
• 2004

In this paper, to detect exciting frequency on the latticed fence structure, fiber optic sensor using Sagnac interferometer was fabricated and tested. The latticed structure fabricated with dimension of 180 cm wide and 180 cm high, the optical fiber, 50 m in length, distributed and fixed on the latticed structure. Single mode fiber, a laser with 1,550 m wavelength, and $3{\times}3$ coupler were used. Excited vibration signal applied to the latticed structure from 200 Hz to 1 KHz. The detected optical signals were compared to the detected acceleration signals and analyzed on the time and frequency domain. Based on the experimental results, fiber optic sensor using Sagnac interferometer detected exciting frequency, effectively. This system can be applied to the structural health monitoring system.

• 한국구조물진단유지관리공학회 논문집
• /
• 제3권3호
• /
• pp.237-243
• /
• 1999

Recently, there has been considerable interest in the development of fiber-optic sensors based on fiber Bragg gratings (FBGs), which can be made into Ge-doped fiber's core by UV phase mask or holographic methods. A good sensitivity and small size of this sensor make it an ideal candidate for distributed sensing in smart structures or other structural monitoring applications. In this study, fiber optic Bragg grating sensor, which could be applied to measure the absolute strains, was constructed and the strain sensitivity of this sensor was investigated in order to apply to the structural health monitoring. Fiber Fabry-Perot (FFP) filter has been used to detect the optical signals instead of optical spectrum analyzer. It has been convenient to determine the structural strains from the output signal of FBGs. The fiber optic Bragg grating sensor was attached on the aluminum beam near the electrical strain gage to measure the same strain. The relationship between strain and fiber signal was linearly fitted. The strain sensitivity of the fiber optic Bragg grating sensor was determined as $l.57{\mu}{\varepsilon}/{\mu}sec$ from the aluminum beam test.

• Smart Structures and Systems
• /
• 제18권3호
• /
• pp.405-423
• /
• 2016

In this study, the feasibility of using telecommunication single-mode optical fiber (SMF) as a distributed fiber optic strain and crack sensor was evaluated in concrete pavement monitoring. Tensile tests on various sensors indicated that the $SMF-28e^+$ fiber revealed linear elastic behavior to rupture at approximately 26 N load and 2.6% strain. Six full-scale concrete panels were prepared and tested under truck and three-point loads to quantify the performance of sensors with pulse pre-pump Brillouin optical time domain analysis (PPP-BOTDA). The sensors were protected by precast mortar from brutal action during concrete casting. Once air-cured for 2 hours after initial setting, half a mortar cylinder of 12 mm in diameter ensured that the protected sensors remained functional during and after concrete casting. The strains measured from PPP-BOTDA with a sensitivity coefficient of $5.43{\times}10^{-5}GHz/{\mu}{\varepsilon}$ were validated locally by commercial fiber Bragg grating (FBG) sensors. Unlike the point FBG sensors, the distributed PPP-BOTDA sensors can be utilized to effectively locate multiple cracks. Depending on their layout, the distributed sensors can provide one- or two-dimensional strain fields in pavement panels. The width of both micro and major cracks can be linearly related to the peak strain directly measured with the distributed fiber optic sensor.

• Journal of the Optical Society of Korea
• /
• 제8권4호
• /
• pp.168-173
• /
• 2004

Brillouin scattering-based fiber optic sensors are useful to measure strain or temperature in a distributed manner. Since the Brillouin frequency of an optical fiber depends on both the strain and temperature, it is very important to know whether the Brillouin frequency shift is caused by the strain change or temperature change. This article presents a temperature compensation technique of a Brillouin scattering-based fiber optic strain sensor. Both the changes of the Brillouin frequency and the Brillouin gain power is observed for the temperature compensation using a BOTDA sensor system. Experimental results showed that the temperature compensated strain values were highly consistent with actual strain values.

• 센서학회지
• /
• 제10권1호
• /
• pp.16-23
• /
• 2001

국부적인 측정을 수행하는 일반적인 광섬유 센서에 비해 분포형 광섬유 센서는 광섬유의 길이방향을 따라 모든 위치에서 측정이 가능하며 보다 넓은 영역의 측정을 수행할 수 있다. 브릴루인 산란 분포형 광섬유 센서를 구조물의 건전성 감시에 이용할 때에는 광섬유 센서의 일반적인 부착 방법인 에폭시를 이용한 표면부착 방법을 사용하게 된다. 본 논문에서는 에폭시를 이용하여 브릴루인 분포형 광섬유 센서를 구조물의 표면에 부착하였을 때 구조물의 변형률 변화를 광섬유 센서가 정확히 측정해 낼 수 있는지에 대해 유한요소법을 통한 검증을 수행하였다. 구조물로부터 에폭시, 광섬유 코팅, 클래딩을 통해 코어로 전달되는 변형률의 전달률을 해석을 통해 확인하였으며 변형률 분포로부터 에폭시 끝 단의 자유 경계면이 미치는 영향을 살펴보았다.

• 한국광학회:학술대회논문집
• /
• 한국광학회 2001년도 하계학술발표회
• /
• pp.118-119
• /
• 2001