Numerical modeling of deposition kinetics in the MCVD process for silica-based optical fibers

Abstract

This study presents a numerical approach for modeling the kinetics of the Modified Chemical Vapor Deposition (MCVD) process under laminar flow conditions, aiming at controlling the refractive index profile in silica-based optical fibers for high-power laser applications. The model couples the steady-state energy and mass transport equations, solved using the Finite Volume Method (FVM) through a commercial CFD package, and the Finite Difference Method (FDM). Simulations yielded velocity and temperature fields of the carrier gas (O2), as well as concentration fields of reactants and oxidation products. Deposition efficiency was estimated by combining thermophoretic velocity and local species concentrations, revealing a slightly higher efficiency for SiO2 compared to GeO2 across all tested scenarios. A parametric analysis was conducted to assess the influence of peak torch temperature and mass flow rate on deposition behavior. Particle trajectories were obtained via a Lagrangian approach using Euler’s integration method, showing that particles closer to the tube wall exhibited greater deposition tendencies due to stronger thermal gradients.