Practical aspects in the drawing of an optical fiber

Abstract

The transport processes in the furnace for the continuous drawing of optical fibers have been studied numerically and analytically. Practical circumstances and operating conditions are considered. A peripheral gas flow configuration has been modeled, along with irises at the ends, as employed in practical furnaces. The neck-down profile of the fiber is not chosen, but has been generated on the basis of a surface force balance. The results obtained are validated by comparisons with earlier experimental results. A detailed analysis has been carried out to determine the relative contributions of different forces during the drawing process. Even though the internal viscous stress is shown to be the major contributor to the draw tension, it is found that under certain operating conditions, the force due to gravity is significant, especially at the beginning of the neck-down region. For a peripheral flow configuration, the effect of flow entrance is found to be very important in determining the necking shape. However, the effect of the iris size on the fiber temperature field is found to be negligible. It is found that for a given furnace temperature and fiber radius, there is an upper limit for draw-down speed at which a fiber can be drawn without rupture. Practical ranges of draw speeds and furnace temperature conditions are identified for the process to be feasible.

Optimization of a thermal manufacturing process: Drawing of optical fibers

“…Thus, coupled conduction, convection and radiation heat transfer mechanisms are involved in the analysis. Several earlier papers have presented the analysis and the numerical scheme [8][9][10][11][12][13][14] and only a few important aspects are included here for completeness. For further details, these references may be consulted.…”

“…A low value of the tension is desirable from fiber quality considerations and a large value could result in viscous rupture of the fiber [8,13]. A thermally induced defect, known as the E 0 point defect, is generated due to the breaking of the bond between silicon and oxygen and is of particular interest in fiber quality.…”

“…Experimental results at relatively low draw speeds of up to 3 m/s and for isothermal and parabolic temperature distributions for relatively short furnaces of length around 30 cm were employed. Several of these comparisons have been given in earlier papers [13,21,24,25] and are not repeated here for conciseness.…”

“…This can cause the redistribution of the material dopants and impurities and, therefore, impact the fiber quality [13,20,22]. The variation of the maximum velocity lag in the neck-down region is shown in Fig.…”

Effect of Furnace Thermal Configuration on Optical Fiber Heating and Drawing

“…Dianov et al [4], Vasilijev et al [5], and Papamichael [6] considered isothermal heating zones. A piecewise linear temperature profile over three regions was employed by Xiao [7], Lee and Jaluria [8], and Roy Choudhury and Jaluria [9]. Yin and Jaluria [10] considered different wall temperature distributions for a range of fiber drawing simulations.…”