PCVD process of making optical fiber rod in high deposition rate

Abstract

THe PCVD process of depositing pure silicon layer or doped silica layer in the inner wall of circular quartz lining tube includes the flow of material gas via the quartz lining tube, the periodical rotation of the quartz lining tube through the tubular resonant cavity and the reciprocation of the resonant cavity along the quartz lining tube. It features the high frequency power output of the high frequency system up to 3-6 KW; reactant gas flow rate including pure SiCl4 vapor 800-2000 sccm, O2 1500-5000 scm, pure GeCl4 vapor 20-500 sccm and pure Freon vapor 10-100 sccm; and the maximum deposit rate 1.80-3.50 g / min. After deposition, the deposited tube is melted and contracted in a contracting equipment into solid core rod. The present invention has high deposit rate and thus high production efficiency.

Description

technical field [0001] The invention relates to a preparation process of an in-pipe optical fiber core rod, especially a plasma chemical vapor deposition process (that is, a PCVD process) with a relatively high deposition rate and deposition efficiency to manufacture a silica optical fiber core rod for communication. Background technique [0002] The manufacturing process of silica (glass) optical fiber for communication generally includes two processes of rod making and wire drawing. Since the transmission characteristics of the optical fiber mainly depend on the core rod part, the core rod manufacturing process is considered to be the core technology of the optical fiber manufacturing process. At present, the processes used to make silica fiber core rods can be divided into in-tube methods and out-of-tube methods according to different implementation methods. The in-tube methods mainly include improved chemical vapor deposition (MCVD) and plasma chemical vapor deposition (P...

AI Technical Summary

Problems solved by technology

[0003] Since the external deposition process adopts the epitaxial deposition method, the deposition rate mainly depends on the reaction gas flow rate and is not affected by the temperature field of the heat source, which can reach a very high actual value, but the actual deposition efficiency of the external deposition process is also seriously affected by the reaction. The influence of the effective contact area between the gas flow and the target rod, especially for the manufacturing process of the core rod at the beginning of the vapor deposition, which reflects the opposite trend of the deposition efficiency and the deposition rate, such as the current conventional OVD process in the manufacture of ordinary single-mode cores The average deposition efficiency is less than 50% when rod

Although the heat source used in the PCVD process—high-frequency microwaves can directly act on the reaction gas, the deposition rate is difficult to significantly increase due to the size and stability of the output power of the high-frequency microwave system. For example, the existing fourth-generation PCVD deposition equipment, its stable output can reach a maximum power of about 3 kilowatts, and the corresponding deposition rate is difficult to exceed 1.8g / min

Therefore, compared with the external vapor deposition process, although the PCVD process can precisely control the complex refractive index profile of the core rod, the problem of low deposition rate has always been the technical bottleneck restricting the high-efficiency manufacturing of optical fiber preforms by the in-tube method.