• Proceedings of the Optical Society of Korea Conference
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• 1999.08a
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• pp.226-227
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• 1999

In the fiber-optic gyroscope employing the erbium-doped fiber source, the source excess noise was subtracted through a signal processing to improve the gyroscope sensitivity . As the result, we obtained the improvement of 14 dB(electrical) at the proper frequency, which was measured from the noise floor spectrum . In addition the random walk coefficient in the gyro output was reduced by about factor of three.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.10a
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• pp.116-120
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• 2001

Fiber fracture is one of the dominant failure phenomena to determine total mechanical properties in composites. Fiber fracture locations were measured by optical microscopic method and acoustic emission (AE) as functions of matrix toughness and surface treatment by the electrodeposition (ED), and then two methods were compared. Two AE sensors were attached on the epoxy specimen and fiber fracture signals were detected with elapsed time. The interfacial shear stress (IFSS) was measured using tensile fragmentation test and AE system. In ED-treated case, the number of the fiber fracture measured by an optical method and AE was more than that of the untreated case. The signal number measured by AE were rather smaller than the number of fragments measured by optical method, since some fiber fracture signals were lost while AE detection. However, one-to-one correspondence between the x-position location by AE and real break positions by optical method was generally established well. The fiber break source location using AE can be a valuable method to measure IFSS for semi- or nontransparent matrix composites nondestructively (NDT).

• Korean Journal of Optics and Photonics
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• v.14 no.4
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• pp.449-453
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• 2003

In a broadband erbium-doped fiber source for fiber optic gyroscope, a pump-polarization scrambling scheme is used to suppress the polarization dependence of the source mean wavelength. The degree of polarization of the pump is reduced to 1.4% by applying proper modulation depth to the polarization modulator where 10 m-long single-mode fiber is wound on a cylindrical PZT. In the case of using the pump-polarization scrambler as well as the output depolarizer, the mean-wavelength variations due to the random change of polarization are measured to be less than our measurement limit of 5 ppm.

• Korean Journal of Optics and Photonics
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• v.6 no.4
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• pp.324-330
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• 1995

Stimulated Brillouin scattering theory is described in an optical fiber. Frequency change with an optical heterodyne method is analyzed between reference signal of a source and stimulated Brillouin scattering signal in an optical fiber. By coupling a source with a few axial modes and an optical fiber ring resonator, Brillouin scattering is studied with a spectrum analyzer. Using reference beating signal of a source, we have reduced the Brillouin beating frequency from 13 GHz range to below GHz. Experimentally, we can see the Brillouin beating frequency from 13 GHz range to below GHz with a dispersion shifted fiber (1.32 GHz), Ti-doped fiber (900 MHz) and single mode optical fiber (870 MHz). MHz).

• Journal of the Optical Society of Korea
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• v.13 no.2
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• pp.240-244
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• 2009

An Er-doped superfluorescent fiber source is designed and constructed with the double-pass forward configuration, which aims at high stability of its mean wavelength against temperature variation. As a result, thermal stability of mean wavelength better than 1 ppm is obtained against the temperature variation of ${\pm}5^{\circ}C$ around the optimum operating temperature. The optimum operating temperature can be tuned with the Er-doped fiber length and the pump power.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.9
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• pp.1283-1289
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• 2013

The purpose of this study is to find the new method for estiming the spatial variations in a light source with utilizing the optical fiber sensory system. With this aim, firstly the asymmetry in the beam profile of a light source is evaluated by using the tipped optical fiber with 0, 10, 20, 30, 40, 45-degree angle. Secondly the variation of position in a light source is estimated by adjusting the relative position between the light source unit (XYZ stage, LED, Optical fiber) and the receiver unit (Photodiode, XYZ stage). Our experimental results show that the spatial variation of a light source can be resolved in terms of the variations in beam profile with varying the tip angle of an optical fiber and adjusting the relative distance between the light source unit and the receiver.

• Journal of Nutrition and Health
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• v.30 no.7
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• pp.751-769
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• 1997

This study was performed to investigate the effect of chitosan and NOCC from different sources and of different molecular weights on cadmium toxicity. Sprague-Dawley rats were blocked into 26 groups according to body weight, and were raised for 4 weeks. Cadmium chloride was given at the level of 0 or 400 ppm in diet. Various forms of chitosan and NOCC were given at the level of 0 or 4%(w/w) of diet. Cd toxicity was alleviated by various chitosan and NOCC supplements. However, the alleviating effects were different with fiber source(crab and shrimp), type(chitosan and NOCC), and molecular weight (low, medium, and high). Molecular weight had no significant effect. Compared with shrimp-source-fiber-fed groups, crab-source-fiber-fed groups showed lower Cd concentrations in blood and kidney, lower kidney metallothionein concentration, and lower liver and kidney MT-Cd contents. Compared with NOCC -fed groups, chitosan-fed groups showed lower intestine and liver Cd concentrations, lower liver and kidney MT concentrations and MT-Cd content, and higher fecal Cd excretion. Among cadmium-exposed group, low molecular weight shrimp chitosan group showed low Cd concentrations of liver and kidney, high fecal Cd excretions, and the lowest intestine and liver MT concentrations and liver MT-Cd content. In summary, a crab source fiber was more effective than shrimp source fiber, chitosan was more effective than NOCC, and the most effective one in alleviating Cd toxicity was low molecular weight shrimp chitosan.

• Journal of the Optical Society of Korea
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• v.7 no.4
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• pp.216-223
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• 2003

We report a technique that improves the spatial resolution of optical coherence tomography (OCT) by utilizing fiber-based spectral filtering. The proposed technique improves the resolution by filtering out the erbium’s characteristic peak from the amplified spontaneous emission (ASE) source spectrum, and reshaping the spectrum to Gaussian-like. We used a long period fiber grating (LPG) and an erbium doped fiber (EDF) absorber for the spectral filtering. An in-house made ASE source as well as a commercial ASE source [ASE-FL7002] was used as the OCT sources to study the proposed technique. The resolution of the OCT based on an in-house made ASE source is enhanced from 200 to 40 ㎛ with an LPG. While, the resolution of the OCT based on a commercial ASE source is enhanced from 25 to 19 ㎛ with the aid of an EDF absorber. However, sidelobes still exist in the interferogram due to imperfect spectral filtering, which limited the resolution. Further enhancement in the spatial resolution of the OCT system using the ASE source is possible with the aid of cascaded LPGs and/or carefully designed EDF absorber.

• Journal of the Optical Society of Korea
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• v.17 no.4
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• pp.312-316
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• 2013

A novel fiber-optic sensor system is suggested in which fiber Bragg grating sensors are demodulated by a wavelength-sweeping fiber laser source and a spectrometer. The spectrometer consists of a diffraction grating and a 512-pixel photo-diode array. The reflected Bragg wavelength information is transformed into spatial intensity distribution on the photo-diode array. The peak locations linearly correspond to the Bragg wavelengths, regardless of the nonlinearities in the wavelength tuning mechanism of the fiber laser. The high power density of the fiber laser enables obtaining high signal-to-noise ratio outputs. The improved demodulation characteristics were experimentally demonstrated with a fiber Bragg grating sensor array with 5 gratings. The sensor outputs were in much more linear fashion compared with the conventional tunable band-pass filter demodulation. Also it showed advantages in signal processing, due to the high level of photo-diode array signals, over the broadband light source system, especially in measurement of fast varying dynamic physical quantities.

• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.508-510
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• 1995

A fiber-optic pressure sensor is fabricated with a photoelastic glass material. To remove the influence of external pertubation along the optical fiber, a new referencing technique is proposed by using two light sources. LED with 870nm wavelength is used as light source for reference signal, and LED with 660nm wavelength is used as light source for modulation signal. The fiber-optic pressure sensor system shows good linearity within the pressure range of 0 to 5 $kg/cm^2$.