• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.09a
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• pp.475-478
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• 2003

A sol-gel fiber-optic biosensor with encapsulated pH-sensitive fluorophore and immobilized genetically modified toluene-o-xylene monooxygenase was developed to detect TCE, which is carcinogenic chlorinate organic compounds prevailing in ground water. The sensitivity was characterized for the composition of sol-gel, and manufacturing procedure.

• Korean Journal of Optics and Photonics
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• v.2 no.1
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• pp.13-19
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• 1991

Utilizing self-phase modulation effects of a dispersion-shifted fiber and delayline characteristics of two gratings, mode-locked 80 ps pulses at 1.319 $\mu \textrm m$ wavelength from a Nd:YAG laser are compressed to 2.1 ps. This experiment is suitable for studying the transmission characteristics of high energy short pulses along normal fibers in zero dispersion regime.

• Korean Journal of Optics and Photonics
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• v.9 no.2
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• pp.100-103
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• 1998

We proposed a simple and yet effective way of wavelength stabilization for WDM transmission using a temperature compensated fiber grating. This scheme was successfully applied to both DFB LD and EMLD, locking them to their respective reference wavelengths notwithstanding temperature change and RF modulation.

• Current Optics and Photonics
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• v.2 no.4
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• pp.356-360
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• 2018

We demonstrate continuous-wave operation of an all-fiber thulium-holmium codoped laser operating at a wavelength of 1706.3 nm. To realize laser operation in the short-wavelength region of the emission-band edge of thulium in silica fiber, we employ fiber Bragg gratings having resonant reflection at a wavelength around 1700 nm as a wavelength-selective mirror in an all-fiber cavity scheme. We first examine the performance of the laser by adjusting the central wavelength of the in-band pump source. Although a pump source possessing a longer wavelength is observed to provide reduced laser threshold power and increased slope efficiency, because of the characteristics of spectral response in the gain fiber, we find that the optimal pump wavelength is 1565 nm to obtain maximum laser output power for a given system. We further explore the properties of the laser by varying the fiber gain length from 1 m to 1.4 m, for the purpose of power scaling. It is revealed that the laser shows optimal performance in terms of output power and slope efficiency at a gain length of 1.3 m, where we obtain a maximum output power of 249 mW for an applied pump power of 2.1 W. A maximum slope efficiency is also estimated to be 23% under these conditions.

• Korean Journal of Optics and Photonics
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• v.21 no.1
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• pp.12-15
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• 2010

In this paper, we have proposed and demonstrated a simple fiber-optic temperature sensor based on the bending loss of a TEC(thermally expended core) fiber attached to a bi-metal. The deformation of the bi-metal caused by the change in its temperature induces the bending loss of the TEC fiber. The experimental result shows that the temperature sensitivity and operation temperature range of the device are controllable through the adjustment of the structure of the expanded core fiber. The fabrication procedure of the device is described in detail.

• 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.

• Korean Journal of Optics and Photonics
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• v.6 no.4
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• pp.296-301
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• 1995

A single-mode erbium-doped fiber laser is constructed by using a intracore fiber Bragg grating and a unidirectional fiber loop mirror. The laser cavity is designed in such a way that the laser beam forms a travelling wave in the gain medium by placing the erbium-doped fiber inside the unidirectional loop and that the wavelength-selective feedback is made from the outside of the loop by a fiber grating with 0.2 nm reflection linewidth. An additional fiber ring resonator is constructed and used as an optical spectrum analyzer to observe the variation of the laser mode spectra. As the result, relatively stable single mode, single polarization output is observed for the most of the time except some mode hoppings in minute scale due to enviommental temperature variations. tions.

• Current Optics and Photonics
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• v.1 no.5
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• pp.468-473
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• 2017

We determined the feasibility of a fishing camera system using an optical fiber as the fishing line by testing a power-over-fiber (POF) module and multimode optical fiber. Operation of the remote camera module (RCM) without the battery was preferred because the removal of the charging or battery replacement section enabled a waterproof single-body type design. The average efficiency of the photovoltaic power converter (PPC) in the tested POF module was 32.6% at 820 nm, and thus, a high-power laser of at least 1.27 W was required for operating the developed RCM with an electrical dissipation of 413 mW. Because the optical fiber was wound on a fishing reel, composite loss composed of bending and tensile loss occurred. To mitigate the composite loss, we employed a simple holder that showed an improvement in the composite loss of 0.38 dB to 0.8 dB, which was considerably better than the losses without the holder.

• Korean Journal of Optics and Photonics
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• v.14 no.2
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• pp.155-160
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• 2003

We have constructed and characterized a depolarized fiber-optic gyroscope that uses a length of single-mode fiber as a sensing loop fiber. We have also calculated the noise characteristics of the gyroscope and have found an optimum phase modulation depth that gives the highest signal-to-noise ratio in the gyroscope. The random walk coefficient as small as 0.7$\times$10$^{-3}$ deg/√hr was obtained at the modulation depth of around 2.4 rad. The random walk coefficients measured at various modulation depths were found to be in reasonable agreement with the calculation.

• Journal of Korean Ophthalmic Optics Society
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• v.1 no.1
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• pp.15-22
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• 1996

The fine structure of retinal tissue was studied to investigate on effect of Laser irridation on the ICR mouse with electron microscope. The results obtained were as follows: 1. At the normal groups, the most retinal layers were a complex structure, consisting of several specific cells and nerve fiver. 2. In the increasing time of Laser irridation, each cell layer of retina was not uniform of the structure and band. The visual cells were severely heterochromatin swelling of cytoplasm, irregular shape & heterochromatin of nuclear, and disappear of some cytoplasm. The nucleus and nerve fiber of retinal layer was a very irregular shape, formation of vesicle, not identify of each intercellular boundary. The pigment epithelial cells were not an uniform, a large vesicle formation of cytoplasm, and a condensation & very irregular shape of nucleus.