• Journal of the Optical Society of Korea
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• v.7 no.2
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• pp.79-83
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• 2003

In this paper, we describe the fabrication process of a photonic crystal fiber and present the measured optical properties of the photonic crystal fiber. The fabrication of the photonic crystal fiber involves stacking, jacketing, collapsing, and drawing using a conventional drawing tower The photonic crystal fiber drawing needs higher tension to maintain the uniform air hole structure. Thus, the temperature of the photonic crystal fiber drawing is lowered by a few hundred degrees Celsius than for the case of conventional optical fiber drawing. The optical properties of the fabricated photonic crystal fiber such as mode profile, optical loss, transmission spectrum, bending loss, and polarization dependent loss are measured.

• Journal of the Korean Ceramic Society
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• v.19 no.1
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• pp.44-50
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• 1982

Drawing optical fibers in a graphite furnace is one of the most convenient and economical means of producing optical fiber. Since the flaw formation on optical fiber is mainly due to dust contaminations during drawing and surface corrosion by water vapor penetration through coating layer, the tensile strength of optical fiber drawn in a graphite furnace is greatly inflenced by the drawing conditions. The important factors found in this investigation were preform treatment (fire polishing), furnace interior environment (dust contamination, inert gas flows), primary coating condition (resin curing temperature, coating materials, method, thickness) and fiber pulling condition (furnace temperature, drawing speed, pulling tension). The tensile strength at optimum drawing conditions turned out to be 5 ~ 6 GPa.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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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.

• Journal of computational fluids engineering
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• v.16 no.1
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• pp.22-29
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• 2011

In this study, the glass fiber drawing from a silica preform in the furnace for the optical fiber manufacturing process is numerically simulated by considering the radiative heating of cylindrically shaped preform. The one-dimensional governing equations of the mass, momentum, and energy conservation for the heated and softened preform are solved as a set of the boundary value problems along with the radiative transfer approximation between the muffle tube and the deformed preform shape, while the furnace heating is modeled by prescribing the temperature distribution of muffle tube. The temperature-dependent viscosity of silica plays an important role in formation of preform neck-down profile when the glass fiber is drawn at high speed. The calculated neck-down profile of preform and the draw tension are found to be reasonable and comparable to the actual results observed in the optical fiber industry. This paper also presents the effects of key operating parameters such as the muffle tube temperature distribution and the fiber drawing speed on the preform neck-down profile and the draw tension. Draw tension varies drastically even with the small change of furnace heating conditions such as maximum heating temperature and heating width, and the fine adjustment of furnace heating is required in order to maintain the appropriate draw tension of 100~200 g.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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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.

• Journal of Industrial Technology
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• v.22 no.B
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• pp.241-249
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• 2002

Optical fiber is indispensable for optical communication systems that transmit large volumes of data at high speed, but super precision technology in sub-micron units is required for optical axis adjustment. We developed the automatic optical fiber by image processing and automatic loading system. we have developed 6-axis micro stage system for I/O optical fiber arrays, the initial automatic aligning system software for a input optical array by the image processing technique, fast I/O-synchronous aligning strategy, the automatic loading/unloading system and the automatic UV bonding mechanism. In order to adjust the alignment it used on PC based motion controller, a $10{\mu}m$ repeat-detailed drawing of automatic loading system is developed by a primary line up for high detailed drawing. Also, at this researches used the image processing system and algorithm instead of the existing a primary hand-line up and fiber input array and waveguide chip formed in line by automatic.

• Journal of computational fluids engineering
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• v.15 no.4
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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.

• Journal of computational fluids engineering
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• v.16 no.4
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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.

• Journal of computational fluids engineering
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• v.18 no.4
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• pp.69-73
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• 2013

Mass manufacturing of optical fiber includes the process of very thin glass fiber drawing by heating and softening the high purity silica preform and applying the draw tension on the softened tip of preform neck-down profile in a draw furnace. In this computational study, this process is numerically modeled with simplified geometry of the draw furnace which is comprised of essential parts such as concentric graphite heater, muffle tube, and insulation surrounding the heater. The iterative computational scheme is employed between one-dimensional model of neck-down profile prediction and two-dimensional axisymmetric thermo-fluid CFD computation of radiative heating and working gas convection. The computational results show the experimentally observed neck-down profile in heated section of preform, while yielding the reasonable values of draw tension and heater wattage. Also, this study analyzes and discusses the effects of heating conditions such as heater length and temperature on several important aspects of glass fiber drawing process.

• Journal of the Korean Ceramic Society
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• v.40 no.11
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• pp.1102-1105
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• 2003

The fiber drawing process induced defects in silica fiber have been investigated. This study has focused on the Oxygen Deficient Centers (ODCs) and E' centers induced by the fiberization process in low-OH silica fibers. To investigate those defects induced by the fiberization process, the optical absorption spectrum and Electron Spin Resonance (ESR) have both been employed. The concentration of Oxygen Deficient Centers (ODCs) and E' centers are increased by the fiber drawing process. The population of defects in the neck-down region has also been investigated. The most significant generation of defects during fiber drawing process has been shown to occur in this region of silica preform. The population of defects is higher on the edge region than in the center of neck-down region.