Co‐Extrusion of Multilayer Glass Fiber‐Optic Preforms: Prediction of Layer Dimensions in the Extrudate

Abstract

A three‐dimensional, incompressible and noncavitating model of a glass‐stack coextrusion process, under isothermal and non‐isothermal conditions is numerically simulated by means of computational fluid dynamics. A dynamic mesh approach is taken in a domain‐subdomain type setup to simulate the transient steps in the steady‐velocity phase of the experimental co‐extrusion. The multiphase setup consists of a glass‐stack which is composed of different glass compositions. Experimentally measured glass properties, such as the temperature coefficient of the viscosity of the supercooled glass melts are used to define the flow behavior of the glasses in the starting stack when extruded. The modeled extrudate is numerically verified for transient and spatial errors, leading to the choice of a suitable mesh. Excellent agreement is found between modeling and experiment when plotting the core/cladding dimensions of a step‐index extruded fiber‐optic preform along the length of the preform. This approach can identify the stable part of the preform, in terms of constant core/cladding layer geometry, obviating costly and time‐consuming experimental iteration. Also, the modeling allows prediction of the starting glass‐stack dimensions for a specified fiber design.

Predictive, Miniature Co‐Extrusion of Multilayered Glass Fiber‐Optic Preforms

“…In contrast, in the present work, using the same CFD framework as described in our earlier work, we have been able to predict the starting stack arrangement and dimensions required to produce the specific layer dimensions for a fiber‐optic preform designed to have four alternating chalcogenide glass layers and made via a miniaturized extrusion (see Fig. ).…”

“…The extruded core‐clad preform for which the CFD model was previously developed was from a previous published work from the same research group …”

“…The miniaturized system had an extruder barrel of ~14 mm internal diameter (ID) (Fig. ) and was able to produce fiber‐optic preforms with less custom‐made glass than in our previous work, using the larger scale extruder, which had an extruder barrel of 30 mm ID . Applying the miniaturized extrusion to a chalcogenide glass‐stack feed, a thin multilayered extrudate of constant OD, of between about 3 and 5 mm, could be directly formed.…”

“…As in our previous work, simulation and experimental results have been compared, here specifically to make the case for the predictive capability of the modeling approach we are proposing for application to multilayered extrusion, even with the additional challenge of using miniaturized extruder dimensions.…”

Low loss Ge-As-Se chalcogenide glass fiber, fabricated using extruded preform, for mid-infrared photonics

“…Extrusion can help achieve low interfacial roughness (i.e. lower scattering loss) in the fabrication of step-index chalcogenide glass fiber [35] and extrusion of chalcogenide glass for fiberoptic preform fabrication has been investigated in several publications [35][36][37][38][39]. In 2008, we reported [35] the co-extrusion of Ge-As-Se/Ge-As-Se-S core/clad.…”