Heat and Mass Transfer in a CVD Optical Fiber Coating Process by Propane Precursor Gas

Abstract

This study investigates an in-line chemical vapor deposition (CVD) process used to hermetically coat optical fibers during manufacture using propane as the precursor gas. Temperature is calculated by coupling radiation and convection heat transfer between the reactor walls and gas flow with a radially lumped conduction heat transfer model for the moving optical fiber. Multicomponent species diffusion is modeled by the Dixon-Lewis method, which is based on the molecular theory for ideal gases. Gas-phase reaction kinetics is modeled using a three-step chemical kinetics mechanism. Surface reaction kinetics are described using collision theory, in which a sticking coefficient is used as an empirical parameter to predict surface reactions. A parametric study is carried out with various optical fiber inlet temperature and drawing speeds, and is validated with experiment results.

Acknowledgments

Financial support by the National Science Foundation and the U.S. Office of Naval Research are gratefully acknowledged. OFS Specialty Photonics Division (Avon, CT) is gratefully acknowledged for valuable discussions on carbon-coated optical fibers.