Estudo de metodologia para produção e análise de preformas de sílica dopadas pelo método MCVD

Abstract

The Modified Chemical Vapor Deposition (MCVD) method is widely used for the production of optical fiber preforms due to its efficiency and precision in controlling the composition and optical properties of the resulting fibers. This work aims to present a study for the development of a methodology to produce doped silica preforms using the MCVD process. To achieve this, a literature review was conducted on the methodology and the most common process parameters applied in the processing of germanosilicate fibers and rare-earth-doped optical fibers, particularly those doped with Yb and Al. Consequently, a methodology with scaled complexity was proposed for the production of these preforms, and a numerical Computational Fluid Dynamics (CFD) model was applied to test the literature data regarding reaction efficiency. CFD simulations were guided by an experimental design model, resulting in numerical outcomes aimed at reducing the costs and time required for conducting experiments. Simulations combined with the rotatable central composite experimental design methodology allowed, within the analyzed operational range, identifying an optimal point for the process occurring at a temperature of 2100 K, with a gas flow rate of 1.9 L/min. The rotation speed of the substrate tube could be maintained at the most convenient level, as it did not show statistically significant changes in the studied response. Additionally, a detailed methodology for analyzing the refractive index profile was described for use with preforms produced by the MCVD method, with experimental results indicating a step-type refractive index fiber.