• Korean Journal of Oriental Medicine
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• v.13 no.3
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• pp.105-110
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• 2007

This work reports the pulse diagnosis system using FBG sensors which can display pulse signals detected while oriental medical doctors are conducting pulse diagnoses and simultaneously pressing the sensors by three fingers. Each optical fiber has five FBG sensing units fabricated in 2 mm width and 2 mm inter-sensor spacing. Three optical fibers with the FBG units in the parallel line configuration are then placed on each finger-pressing region and thus overall 9 fibers are used for the pulse measurements on the so-called "chon", "gwan", and "ch대k". A fixture holding the optical fiber arrays is able to adjust the height of the FBG sensing units while placing the fibers on the wrist. The pulse signals detected by the FBG sensors from chon, kwan, and chuk have been analyzed using 4 channel spectrum analyzer connected to the optical fibers. The measured pulse signals exhibit variations due to the nonuniform pressure distributions applied. resulting in the differences in the detected pulse signals between fiber lines. However. this work is the first step towards objective and quantitative analyses of the pulse diagnosis in oriental medicine which has traditionally been performed on subjective basis. Future works will be devoted to improving sensor stability, developing the way applying pressure and algorithms reporting the objective classification of the pulse status from systemic measurements using the sensors instead of relying on the clinicians' diagnoses subjectively performed. A successful pulse diagnosis system emerging in the future is expected to contribute to education as well as promoting pulse diagnosis in oriental medicine to the scientific research area.

• 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.

• Proceedings of the Optical Society of Korea Conference
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• 2006.07a
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• pp.399-400
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• 2006

Etched fiber Bragg grating, Sensitivity of fiber-Bragg-grating sensors to index of surrounding, Hybridization of DNA

• Korean Journal of Optics and Photonics
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• v.12 no.4
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• pp.294-299
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• 2001

Recently great efforts and investment have been made in order to develop a structural health monitoring technology using fiber optic sensors. Therefore, in this study, we have focused on the development of a fiber optic BOTDA (Brillouin Optical Time Domain Analysis) sensor system in order to measure strains distributed on large structures by an optical fiber. The fiber optic BOTDA sensor was constructed simply, with only two electro-optic modulators. The results of strain measurement tests of an optical fiber showed that the strain can be determined accurately from the Brillouin frequency shift measurement on the strain induced range of 10 m in the total fiber length of 4.8 kIn using 200 averaged signals. Also, the strain sensitivity of Samsung single mode fiber was 4.81 MHz/O.Ol % under the test. test.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.12 s.117
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• pp.1279-1285
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• 2006

In this study, structural deformation estimation using displacement-strain relationship is investigated. When displacements of a structure cannot be measured directly, estimation of displacements using strain data can be an alternative solution. Additionally, the deformation of the whole structure as well as the displacement at the point of interest can be estimated. Strain signals are obtained front Fiber Bragg Grating(FBG) sensors that have an excellent multiplexing ability. Some experiments were performed on two beams and a plate to which FBG sensors were attached in the laboratory. Strain signals from FBG sensors along a single strand of optical fiber were obtained through wavelength division multiplexing(WDM) method. The beams and the plate structures were subjected to various loading conditions, and deformed shapes were reconstructed from the displacement-strain transformation relationship. The results show good agreements with those measured directly from laser sensors. Moreover, the whole structural shapes of the beams and the plate were estimated using only some strain sensors.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.8
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• pp.639-646
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• 2017

In this paper, a new load monitoring system for military aircraft is introduced. This system consists of sensors, an onboard device and an ground analysis equipment. The sensors and onboard device are mounted on the aircraft and the ground analysis equipment is operated on the ground. Through this system, structural static load can be estimated with flight parameters and structural responses can be measured by sensors due to static load, dynamic load and unexpected events. Especially, optical fiber sensors with mutiplexing capability are utilized. The onboard device was specially designed for complying the requirements of relevant military specifications and was verified through a series of the environment tests. This system was used and evaluated through ground structural tests before flight tests. In the near future, this system will be applied to military aircraft as a structural load monitoring system after flight test evaluation.

• Journal of Sensor Science and Technology
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• v.13 no.2
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• pp.121-127
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• 2004

A reflection type optical fiber line sensor based on the speckle detection has been developed using the optical fiber mirror with the reflectance of 72 %. Some experiments were carried on with the automobile and the 500 m length multimod fiber. When the automobile passed on the fiber sensor, two abrupt changes of the output waveform occured like the transmission type sensor based on the speckle variations. The signal to noise ratio of this sensor was about 40 dB.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.9
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• pp.1239-1244
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• 2014

In this study, two fiber-optic sensors were fabricated to measure water level and temperature using optical fibers, a coupler, a Lophine and an OTDR (optical time-domain reflectometer). First, using Fresnel's reflection generated at the distal-ends of each optical fiber, which was installed at different depth, we measured the water level according to the variation of water level. Next, we also measured the temperature of water using a temperature sensing probe based on the Lophine, whose absorbance changes with the temperature. The measurable temperature range of the fiber-optic sensor is from $5^{\circ}C$ to $65^{\circ}C$ because the maximum operation temperature of the optical fiber without a physical deterioration is up to $80^{\circ}C$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.3
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• pp.218-221
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• 2009

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).

• International Journal of Concrete Structures and Materials
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• v.3 no.1
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• pp.33-37
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• 2009

Fiber Bragg grating (FBG) sensors already have been the focus for structural health monitoring (SHM) due to their distinguishing advantages. However, as bare optical fiber is very fragile, bare FBG strain sensor without encapsulation can not properly be applied in practical infrastructures. Therefore encapsulation techniques for making encapsulated FBG strain sensor show very important in pushing forward the application of FBG strain sensors in SHM. In this paper, a simplified approximate method to analyze the stress transferring rules for embedded FBG strain sensors in concrete monitoring is put forward according to mechanics of composite materials. Shear lag theory is applied to analyze the stress transferring rule of embedded FBG strain sensor in measured host material at the first time. The measured host objects (concrete) and the encapsulated FBG strain sensor are regarded as a composite, and then the stress transfer formula and stress transfer coefficient of encapsulated FBG strain sensor are obtained.