• The Journal of Korean Institute of Communications and Information Sciences
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• v.14 no.4
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• pp.307-320
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• 1989

This paper presetns new design of the Modified Chemical Vapor Deposition(MCVD) system for optical fiber preform fabrication. It contains a glass working lathe, raw material supplier and exhaust gas treatment apparatus as fundamental instruments for MCVD process, graded index fiber design, characteristic of process and the experimenta arrangement to measure the refractive index profile of MCVD preforms, respectively. From the investigation results, it is shown that an ideal graded index fiber preform does not exhibit a center dip or bump.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.11
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• pp.3057-3065
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• 1994

An experimental study has been made for heat transfer and particle deposition during the Modified Chemical Vapor Deposition process which is currently utilized to manufacture high quality optical waveguides. The distributions of tube wall temperatures, rates and efficiencies of particle deposition were measured. Results indicate that the temperature distributions of the tube wall in the axial direction yield the quasi-steady form in which temperature distributions fit in one curve if the relative distance from the moving torch is used as an axial coordinate. Due to the repeated heatings from the traversing torch, the wall temperatures are shown to reach the minimum ahead of torch and it is shown that the two torch formulation suggested by Park and Choi is valid to predict this minimum temperature. Measured wall temperatures, particle deposition efficiencies and tapered entry length are compared with the previous modelling results and shown to be in agreement.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.4
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• pp.608-613
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• 2000

The present study has proposed a novel aerosol CVD utilizing an internal jet in the conventional MCVD reactor for the purpose of enhancing the deposition efficiency(and rate) and the uniformity of deposited film. The use of impingement of high temperature jet through a thin inner tube ensures the reduction of non-uniform particle deposition zone as well as higher thermophoretic particle deposition. It is shown that significant improvements have been achieved for both aspects of deposition efficiency and uniformity. As jet temperatures increase, the tapered length is reduced and deposition efficiency is significantly increased.

• Journal of the Korean Ceramic Society
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• v.32 no.11
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• pp.1246-1254
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• 1995

A numerical model for fabrication and deposition of ultrafine SiO2 particles were proposed in the simplified horizontal MCVD apparatus using tube furnace reactor. The model equations such as energy and mass balance equations and the 0th, 1st and 2nd moment balance equations of aerosols were considered in the reactor. The phenomena of SiCl4 chemical reaction, SiO2 particle formation and coagulation, diffusion and thermophoresis of SiO2 particles were included in the aerosol dynamic equation. The profiles of gas temperature, SiCl4 concentration and SiO2 particle volume were calculated for standard conditions. The concentrations, sizes and deposition efficiencies of SiO2 particles were calculated, changing the process conditions such as tube furnace setting temperature, total gas flow rate and inlet SiCl4 concentration.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.5
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• pp.670-677
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• 1999

An analysis of generation and growth of multicomponent particles has been carried out to predict the size and composition distributions of particles generated in the Modified Chemical Vapor Deposition(MCVD) process. In MCVD process. scale-up of sintering and micro-control of refractive index may need the Information about the size and composition distributions of $SiO_2-GeO_2$ particles that are generated and deposited. The present work solved coupled steady equations (axi-symmetric two dimensions) for mass conservation, momentum balance. energy and species(such as $SiCl_4$, $GeCl_4$, $O_2$, $Cl_2$) conservations describing fluid flow. heat and mass transfer in a tube. Sectional method has been applied to obtain multi-modal distributions of multicomponent aerosols which vary in both radial and axial directions. Chemical reactions of $SiCl_4$ and $GeCl_4$ were included and the effects of variable properties have also been considered.

• Proceedings of the Optical Society of Korea Conference
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• 2004.02a
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• pp.124-125
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• 2004

Eu$^{2+}$ doped optical fibers were developed for magneto-optical application by use of CO gas as a reduction agent during MCVD process and the Verdet constant of the Eu$^{2+}$ doped fiber was found to be -0.819[rad/T ${\cdot}$ m], which is three times larger than that of the Eu$^{3+}$ doped fiber.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.5
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• pp.1301-1309
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• 1994

A study of heat transfer and thermophoretic particle deposition has been carried out for the Modified Chemical Vapor Deposition(MCVD) process. A new concept utilizing two torches is suggested to simulate the heating effects from repeated traversing torches. Calculation results for the wall temperatures and deposition efficiency are in good agreement with experimental data. The effects of variable properties are included and heat flux boundary condition is used to simulate the moving torch heating. A conjugate heat transfer which includes heat conduction through solid layer and heat teansfer in a gas in a tube is analyzed. Of particular interests are the effects of torch speeds and solid layer thicknesses on the deposition efficiency, rate and the tapered entry length.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.1
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• pp.212-222
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• 1994

In the annular Modified Chemical Vapor Deposition process using two concentric tubes, the inner tube is heated to maintain high temperature gradients to have high thermophoretic force which can increase particle deposition efficiency. However, higher axial velocity in a narrow gap between inner and outer tubes can result in a longer tapered entry length. In the present paper, a new concept using an annular jet from the inner tube is presented and shown to significantly reduce the tapered entry length with maintaining high efficiency. Effects of a jet injection on heat transfer, fluid flow and particle deposition have been studied. Of particular interests are the effects of jet velocity, jet location and temperature on the deposition efficiency and tapered length . Torch heating effects from both the previous and present passes are included and the effect of surface radiation between inner and outer tubes is also considered.

• Journal of the Optical Society of Korea
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• v.7 no.2
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• pp.47-52
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• 2003

Effect of soaking temperature on erbium doping of the optical fiber core during solution doping procedure, especially in the modified chemical vapor deposition (MCVD) process, was investigated. The concentration of dopants such as $Er^{3+} and Al^{3+}$ in the preforms and the optical fibers measured by the electron probe microanalysis (EPMA) and the optical spectrum analyzer (OSA) was found to increase with decreasing the soaking temperature. The increase in the concentration of the $Er^{3+}$ is attributed to the precipitation of the erbium due to the decrease in the solubility as well as the increase of capillary force and viscosity of the doping solution by decreasing the temperature.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.1
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• pp.79-88
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• 1997

An analysis of unsteady heat and mass transfer in the Modified Chemical Vapor Deposition has been carried out including the effects of chemical reaction and variable properties. It was found that commonly used quasi-steady state assumption could be used to predict overall efficiency of deposition, however, the assumption would not provide detailed deposition profile. The present unsteady calculations of wall temperature profile and deposition profile have been compared with the existing experimental data and were in good agreement. The effects of variable torch speed were studied. Linearly varying torch speed case until time=120s resulted in much shorter tapered entry than the constant torch speed case.