Thermal behavior of optical fibers during the cooling stage of the drawing process

Abstract

A general method that predicts the thermal behavior of optical fibers during the cooling stage of the drawing process was developed. The method can be used for thin diameter D < 200 μm, medium (200 μm < D < 500 μm), and thick (0.5 mm < D < 2 mm) single as well as core-clad fibers. A two-dimensional analysis implementing a finite difference method combined with the Kármán–Pohlhausen technique was performed to obtain the temperature profiles in thick fibers. This method accounted for axial and radial heat conduction, and can also be applied to thin and medium fibers. The case of the core-clad fibers was investigated to obtain the temperature profiles both in the radial and the axial directions. All results are presented in graphical form and can be used for optimization of the drawing process.

Modeling the fabrication of hollow fibers: capillary drawing

“…Thus, the flow is viscosity-dominated, and we may, therefore, conveniently regard (14)- (16) as a regular perturbation problem in . Solving the equations now becomes a simple matter, and we find that (17) (18) (19) where To leading order, the temperature dependence in this problem, therefore, appears only via the ratio of the surface tension to the viscosity. Equations (17)- (19) can be used to predict the degree of collapse in the final structure, and suggest that this depends only upon the ratio of the surface tension to the viscosity.…”

“…4. Experimental results (symbols) and theoretical predictions using (19) for drawn outer capillary diameter as functions of draw speed for a range of furnace temperatures and feed speeds.…”

“…The theoretical predictions from (19) are indicated by solid lines in Figs. 4 and 5, and were calculated as follows.…”

“…In [18], Dewynne et al proposed an asymptotic model of fiber drawing that was essentially similar to [16], but showed that, unless the initial conditions possess certain singularities, the cross-sectional area cannot be made to vanish in finite time. A number of purely numerical studies of optical-fiber drawing have also been made (see, for example [19], [20], and [21]). It does not appear, however, that any detailed theory has yet been proposed for fibers that have a cross section containing holes.…”

Geometry design in rerfractive capillary optical fibers

“…The refractive structure of the cladding is uniform or has index depression around the core. Fabrication techniques of a discrete COF differ for pure or high silica glasses and soft glasses and include: an MCVD preform with incomplete collapsing, hollow core preform or pressurized multicrucible [1][2][3][4][5][6][7][8][9]. A fiber of outside diameter d f is fabricated from a preform of outside diameter d p.…”