• 한국신뢰성학회:학술대회논문집
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• 한국신뢰성학회 2004년도 정기학술대회
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• pp.147-151
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• 2004

In this study, an optical fiber assembly directly coupled with a laser diode or a photo diode is designed to confirm high reliable optical coupling efficiency of optical transmitter(Tx) and receiver(Rx). The optical fiber assembly is fabricated by soldering an optical fiber and a Kovar ferrule using a glass solder after inserting an optical fiber through a Kovar ferrule. The Kovar which has good welding characteristics is applied to introduce laser welding technique. The glass solder has excellent thermal characteristics such as thermal shift delamination compared with PbSn, AuSn solder previously used usually. Furthermore, the glass solder doesn't need fiber metalization and this enables low cost fabrication. However, the glass soldering is high temperature process over 35$0^{\circ}C$ and the convex shape after solidification due to surface tension causes the stress concentration on optical fiber. The stress concentration on the optical fiber increases the optical insertion loss and possibility of crack formation. The shape of glass solder was designed referring to 2-D Axi-symmetric FEM simulation. To test the mechanical reliability, mechanical vibration test and shock test were done according to Telcorida GR-468-Core protocol. After each test, the optical loss of the stress distributed fiber assembly didn't exceed 0.5 dB, which passes the test.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2011년 춘계학술대회논문집
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• pp.92-95
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• 2011

In manufacturing optical fibers, the process starts with the glass fiber drawing from the heated and softened silica preform in the furnace, and the freshly drawn glass fiber is still at high temperature when it leaves the glass fiber drawing furnace. It is necessary to cool down the glass fiber to the ambient temperature before it then enters the fiber coating applicator, since the hot glass fiber is known to cause several technical difficulties in achieving high quality fiber coating. As the fiber drawing speed keeps increasing, a current manufacturing of optical fibers requires a dedicated cooling unit with helium gas injection. A series of three-dimensional flow and heat transfer computations are carried out to investigate the effectiveness of fiber cooling in the fiber cooling unit. The glass fiber cooling unit is simplified into the long cylindrical enclosure at which the hot glass fiber passes through at high speed, and the helium is being supplied through several injection slots of rectangular shape along the cooling unit. This study presents and discusses the effects of helium injection rates on the glass fiber cooling rates.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2011년 춘계학술대회논문집
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• pp.88-91
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• 2011

Glass fiber drawing from a silica preform is one of the most important processes in optical fiber manufacturing. High purify silica preform of cylindrical shape is fed into the graphite furnace, and then a very thin glass fiber of 125 micron diameter is drawn from the softened and heated preform. A computational analysis is performed to investigate the heat transfer characteristics of preform heating and the glass fiber drawing in the furnace. In addition to the dominant radiative heating of preform by the heating element in the furnace, present analysis also includes the convective heat transport by the gas flowing around the preform that experiences neck-dawn profile and the freshly drawn glass fiber at high fiber drawing speed. The computational results present the effects of gas flow on the temperature of preform and glass fiber as well as the neck-down profile of preform.

• 한국전산유체공학회지
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• 제16권4호
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• pp.110-115
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• 2011

A modern optical fiber manufacturing process requires the sufficient cooling of glass fibers freshly drawn from the heated and softened silica preform in the furnace, since the inadequately cooled glass fibers are known to cause improper polymer resin coating on the fiber surface and to adversely affect the product quality of optical fibers. In order to greatly enhance the fiber cooling effectiveness at increasingly high fiber drawing speed, it is necessary to use a dedicated glass fiber cooling unit with helium gas injection between glass fiber drawing and coating processes. The present numerical study features a series of three-dimensional flow and heat transfer computations on the cooling gas and the fast moving glass fiber to analyze the cooling performance of glass fiber cooling unit, in which the helium is supplied through the discretely located rectangular injection holes. The air entrainment into the cooling unit at the fiber inlet is also included in the computational model and it is found to be critical in determining the helium purity in the cooling gas and the cooling effectiveness on glass fiber. The effects of fiber drawing speed and helium injection rate on the helium purity decrease by air entrainment and the glass fiber cooling are also investigated and discussed.

• E2M - 전기 전자와 첨단 소재
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• 제10권3호
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• pp.210-216
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• 1997

The th ermal and optical properties of multicomponent oxide glass optical fiber by adding heavy metal oxide Ga$_{2}$O$_{3}$(0-20wt%) were investigated. The fiber samples were made by the method of rod in tube. The optical loss of fiber was measured in 0.3-1.8.mu.m wavelength region. As Ga$_{2}$O$_{3}$ increased up to 20wt%, the transition and softening temperature of bulk glass were increased from 495.deg. C to 579.deg. C and from 548.deg. C to 641.deg. C, respectively. Whereas the thermal expansion coefficient was decreased from 102 to 79.1x10$^{-7}$ /.deg. C. The refractive index was increased from 1.621 to 1.665, and IR cut-off wavelength was enlarged from 4.64.mu.m to 6.1.mu.m. The optical loss of fiber was remarkably decreased in 1.146.mu.m-1.8.mu.m wavelength region.

• 한국산학기술학회논문지
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• 제3권2호
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• pp.89-93
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• 2002

PbO 함유 다성분계유리 및 파이버를 제조하였으며, PbO함유 유리는 이중도가니법(double crucible methodo에 의한 높은 개구수를 갖는(high-numerical aperture : N.A.) 광파이버(optical fiber) 제조에 적합하였다. 본 실험에 있어서는 SiO₂, PbO를 주성분으로 하고 K₂O, Na₂O, B₂O₃, A1₂O₃등의 산화물을 적량 배합하였으며, 또한 double crucible method에 의해 제조된 파이버의 광학적, 기계적 및 구조적 특성을 관찰하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1994년도 추계학술대회 논문집
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• pp.21-23
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• 1994

By adding La₂O₃ to optical multicomponent glass composition, after making mother glass and core fiber that enable to enlarge the infrared transmittance region, then surveyed the optical properties. Through thermal analysis of the glass abstained by melt-quenching after selecting stable basic composition on devitrification and replace SiO₂ by 4-12wt% La₂O₃. As La₂O₃ increases up to l2wt% transition temperature, refractive index, density, deformation temperature increased, whereas thermal expansion coefficient decreased. As a result of inspectig transmittance in UV/VIS/IR region, visable region indicated the decrease of transmittance by increasing the La₂O₃ and transmittance region was enlarged by increasing the La₂O₃ in IR region. Also, fabricate core fiber at 820℃ and severy the optical loss we could fact that La₂O₃ composition added 12wt% showed the minimum optical loss.

• 한국전산유체공학회지
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• 제15권4호
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• pp.92-98
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• 2010

In a modern high speed drawing process of optical fibers, it is necessary to use helium as a cooling gas in a glass fiber cooling unit in order to sufficiently cool down the fast moving glass fiber freshly drawn from the heated silica preform in the furnace. Since the air is entrained unavoidably when the glass fiber passes through the cooling unit, the helium is needed to be injected constantly into the cooling unit. The present numerical study investigates and analyzes the air entrainment using an axisymmetric geometry of glass fiber cooling unit. The effects of helium injection rate and direction on the air entrainment rate are discussed in terms of helium purity of cooling gas inside the cooling unit. For a given rate of helium injection, it is found that there exists a certain drawing speed that results in sudden increase in the air entrainment rate, which leads to the decreasing helium purity and therefore the cooling performance of the glass fiber cooling unit. Also, the helium injection in aiding direction is found to be more advantageous than the injection in opposing direction.

• ETRI Journal
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• 제27권4호
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• pp.411-417
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• 2005

$Pr^{3+}-doped$ selenide glass optical fiber, which guarantees single-mode propagation of above at least 1310 nm, has been successfully fabricated using a Ge-Ga-Sb-Se glass system. Thermal properties such as glass transition temperature and viscosity of the glasses have been analyzed to find optimum conditions for fiber drawing. Attenuation loss incorporating the effects of an electronic band gap transition, Rayleigh scattering, and multiphonon absorption has also been theoretically estimated for the Ge-Ga-Sb-Se fiber. A conventional double crucible technique has been applied to fabricate the selenide fiber. The background loss of the fiber was estimated to be approximately 0.64 dB/m at 1650 nm, which can be considered fairly good. When excited at approximately 1470 nm, $Pr^{3+}-doped$ selenide fiber resulted in amplified spontaneous emission and saturation behavior with increasing pump power in a U-band wavelength range of 1625 to 1675 nm.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1996년도 추계학술대회 논문집
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• pp.128-134
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• 1996

In this study, the thermal and optical properties of multicomponent glass optical fiber by adding heavy metal oxide Ga$_2$O$_3$were investigated. The fiber samples were made by rod in tube method. The optical loss of fiber was measured in 0.3~1.8${\mu}{\textrm}{m}$ wavelength region. As Ga$_2$O$_3$increased up to 20wt%, the transition and softening temperature of bulk glass were increased from 495$^{\circ}C$ to 579$^{\circ}C$ and from 548$^{\circ}C$ to 641$^{\circ}C$respectively. Whereas the thermal expansion coefficient was decreased from 102 to 79.1$\times$10$^{-7}$ $^{\circ}C$. The refractive index was increased from 1.621 to 1.665, and IR cut-off wavelength was enlarged from 4.64${\mu}{\textrm}{m}$ to 6.1${\mu}{\textrm}{m}$. The optical loss of fiber was decreased and more remarkably decreased in 1.146${\mu}{\textrm}{m}$~1.8${\mu}{\textrm}{m}$ wavelength region.