Numerical Simulation of Transport in Optical Fiber Drawing with Core–Cladding Structure

2006 ◽  
Vol 129 (4) ◽  
pp. 559-567 ◽  
Author(s):  
Chunming Chen ◽  
Yogesh Jaluria
Keyword(s):  
Refractive Index ◽  
Optical Fiber ◽  
Optical Fibers ◽  
Finite Difference Methods ◽  
Initial Study ◽  
Fiber Drawing ◽  
Zonal Method ◽  
The Core ◽  
Optical Fiber Drawing ◽  
Purge Gas

Optical fibers are typically drawn from silica preforms, which usually consist of two concentric cylinders called the core and the cladding, heated in a high-temperature furnace. For optical communication purposes, the core always has a higher refractive index than the cladding to obtain total internal reflection. In order to investigate the effect of this core–cladding structure on optical fiber drawing, a numerical model has been developed in this work. Axisymmetric flows of a double-layer glass and aiding purge gas in a concentric cylindrical furnace are considered. The thermal and momentum transport in both glass layers and gas are coupled at the interface boundaries. The neck-down profile is generated using an iterative numerical scheme. The zonal method is applied to model the radiation transfer in the glass preform. The gas is taken as nonparticipating. Coordinate transformations are used to convert the resulting complex domains into cylindrical regions. The stream function, vorticity, and energy equations for the core, the cladding, and the purge gas are solved by finite difference methods, using a false transient approach coupled with the alternating direction implicit method. A second-order differencing scheme is used for discretization. The numerical results are validated by comparing with results available in the literature. The effects of changes in the refractive index and absorption coefficient due to doping on fiber drawing are investigated. This problem has received very little attention in the literature, particularly with respect to modeling, and this paper presents an initial study of the underlying transport.

Numerical Simulation of Transport in Optical Fiber Drawing With Core-Cladding Structure

2004 ◽  
Author(s):  
Chunming Chen ◽  
Yogesh Jaluria
Keyword(s):  
Optical Fiber ◽  
Optical Fibers ◽  
Numerical Results ◽  
Fiber Drawing ◽  
Zonal Method ◽  
The Core ◽  
Optical Fiber Drawing ◽  
Cylindrical Furnace ◽  
Purge Gas ◽  
Energy Equations

Optical fibers are typically heated and drawn from silica preforms, which usually consist of two concentric cylinders called the core and the cladding, in a high-temperature furnace. For optical communication purpose, the core always has a higher refractive index than the cladding. In order to investigate the effect of core-cladding structure on the optical fiber drawing, a numerical model has been developed in this work. Axisymmetric flows of a double-layer glass and aiding purge gas in a concentric cylindrical furnace are considered. The thermal and momentum transport in both glass layers and gas are coupled at the interface boundaries. The neck-down profile is generated using an iterative scheme. The zonal method is applied to model the radiation transfer in the glass preform and the gas. Coordinate transformations are used to convert complex domains into cylinders. Stream function, vorticity and energy equations for the core, the cladding and the purge gas are solved by finite different methods using a false transient method coupled with an alternating direction implicit (ADI) method. A second order differencing scheme is used for discretization. The numerical results are validated by comparing with experimental and numerical results available in the literature.

Thermal Transport and Flow in High-Speed Optical Fiber Drawing

1998 ◽  
Vol 120 (4) ◽  
pp. 916-930 ◽  
Author(s):  
Zhilong Yin ◽  
Y. Jaluria
Keyword(s):  
Optical Fiber ◽  
Thermal Transport ◽  
High Speed ◽  
Radiative Transport ◽  
Gas Velocity ◽  
Furnace Temperature ◽  
Fiber Drawing ◽  
Zonal Method ◽  
Optical Fiber Drawing ◽  
Purge Gas

The thermal transport associated with optical fiber drawing at relatively high drawing speeds, ranging up to around 15 m/s, has been numerically investigated. A conjugate problem involving the glass and the purge gas regions is solved. The transport in the preform/fiber is coupled, through the boundary conditions, with that in the purge gas, which is used to provide an inert environment in the furnace. The zonal method, which models radiative transport between finite zones in a participating medium, has been employed to compute the radiative heat transfer in the glass. The flow of glass due to the drawing process is modeled with a prescribed free-surface neck-down profile. The numerical results are compared with the few that are available in the literature. The effects of important physical variables such as draw speed, purge gas velocity and properties, furnace temperature, and preform diameter on the flow and the thermal field are investigated. It is found that the fiber drawing speed, the furnace temperature, and the preform diameter have significant effects on the temperature field in the preform/fiber, while the effects of the purge gas velocity and properties are relatively minor. The overall heating of the preform/fiber is largely due to radiative transport in the furnace and the changes needed in the furnace temperature distribution in order to heat the glass to its softening point at high speeds are determined.

Thermodynamic Properties and Optimized Fiber-Drawing Condition in Germanium Tellurite Glasses

2013 ◽  
Vol 275-277 ◽  
pp. 2002-2005
Author(s):  
Fang Fang Fu ◽  
Yu Lei ◽  
Jie Yang ◽  
Zhi Qiang Wang ◽  
Xin Zhao ◽  
...  
Keyword(s):  
Thermodynamic Properties ◽  
Optical Fibers ◽  
Coefficient Of Thermal Expansion ◽  
Softening Temperature ◽  
Optical Devices ◽  
Fiber Drawing ◽  
The Core ◽  
Onset Crystallization Temperature ◽  
Optical Fiber Drawing ◽  
Temperature Reference

Thermodynamic properties of the heavy metal germanium tellurite (NZPGT) core and cladding glasses have been investigated. Coefficient of thermal expansion (CTE) and softening temperature (Ts) of the Er3+⁄Yb3+ codoped NZPGT core glasses were identified to be 1.89×10–5 °C–1 and 343 °C, respectively. Glass transition temperature (Tg), onset crystallization temperature (Tx), peak temperature of crystallization (Tc), temperature difference value (ΔT) and thermal stability parameter (H) of the core glasses were solved to be 290 °C, 412 °C, 470 °C, 122 °C and 0.42, respectively, and the corresponding vaules of cladding glasses were derived to be 290 °C, 391 °C, 400 °C, 101 °C and 0.35. The investigation results indicate optical fiber drawing of Er3+⁄Yb3+ codoped medium-low phonon energy NZPGT glasses can be achieved in the temperature range 345—380 °C, which provides a valuable temperature reference for further high-quality optical fibers drawing in developing optical devices.

A Computational Investigation of Thermal Effects on Resin Coating Flows in an Optical Fiber Drawing System

2011 ◽  
Vol 110-116 ◽  
pp. 1080-1086
Author(s):  
Kyoung Jin Kim ◽  
Ho Sang Kwak ◽  
Jin Su Choi
Keyword(s):  
Optical Fiber ◽  
Optical Fibers ◽  
Thermal Effects ◽  
Resin Flow ◽  
Fiber Drawing ◽  
Coating Flows ◽  
Drawing Speed ◽  
Drawing System ◽  
Optical Fiber Drawing ◽  
Fiber Manufacturing

In manufacturing optical fibers, there has been intense research efforts of continually increasing fiber drawing speed to improve productivity. However, higher speed fiber drawing poses new challenge in many areas of optical fiber manufacturing. In this paper, thermal effects on coating resin flow in an unpressurized coating applicator are studied numerically. Present simulation results found that higher fiber drawing speed leads to severe viscous heating in coating resin flow and significant increase of resin temperature, which in turn leads to substantial viscosity decrease. These thermal effects profoundly alter the resin flow patterns and velocity profiles in the coating die and they should be considered in controlling the final coating thickness.

Fabrication of Optical Fiber Sensors Based on Femtosecond Laser Micro Machining

2020 ◽  
Vol 8 (4) ◽  
Author(s):  
Fengfeng Zhou ◽  
Seunghwan Jo ◽  
Xingyu Fu ◽  
Jung-Ting Tsai ◽  
Martin Byung-Guk Jun
Keyword(s):  
Refractive Index ◽  
Femtosecond Laser ◽  
Optical Fiber ◽  
Refractive Index Change ◽  
Optical Fiber Sensors ◽  
Objective Lens ◽  
Machining Parameters ◽  
Fiber Sensors ◽  
The Core ◽  
First Time

Abstract In this research, we proposed fabrication process of optical fiber sensors using femtosecond laser and their applications. A beam of femtosecond laser was focused by an objective lens in the optical fiber. By testing different conditions, a group of machining parameters was found that achieve a minimum machining resolution of 3.2 μm. To ablate the core of the optical fiber, which is buried deep inside the cladding, precisely, part of the cladding was removed to expose the core as close as possible to the air. By making a complex pattern to modify the optical path of the laser inside an optical fiber, a sensitivity of 942.8–1015.6 nm per refractive index unit (nm/RIU) was obtained for liquid refractive index sensing. For another sensor, a sensitivity of 1.38 × 105 nm/RIU was obtained, which is high enough to detect small amount of refractive index change of air. It is known to be the first time that we fabricated a complex microstructure in an optical fiber to modify the propagation of the light using femtosecond laser. This research shows the possibility of a complex modification of light in an optical fiber using laser machining.

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