This study investigates the chemical vapor deposition (CVD) process used to hermetically coat optical fibers during draw using propane as the precursor gas. Temperature is calculated by coupling radiation and convection heat transfer from the reactor walls and gas flow with a radially-lumped conduction heat transfer model for the moving optical fiber. Multi-component 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 3-step gas phase chemical kinetics mechanism. Surface reaction kinetics is described using collision theory in which a sticking coefficient is used as an empirical parameter to predict surface reactions. A parameter study is carried out with various optical fiber inlet temperature and drawing speed, and validated with experiment results.

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