PCVD method for making large-diameter fibre-optical mandrel

Abstract

The invention relates to a PCVD manufacturing method for an optical fiber mandrel with large diameter. The external diameter of a quartz liner is determined to be 36-46mm, the inner diameter to be 32-40mm and the length of the liner to be 1.45-1.85m for the process of PCVD. Parameters of a processing technology are that the high frequency power of a microwave resonator is controlled to be 6KW-15KW and the deposition temperature is 1080-1130 degree Celsius. The variety of mixed air flowing through the liner includes silicon tetrachloride vapor, germanium tetrachloride vapor, high-purity oxygenand Freon. The inside pressure of the liner is 10-15millibar. The air flow rate inside the liner is 30-80m / s. the air volumetric flow rate is 4400-8800SCCM. The invention solves a technical problem of unstable plasma caused by the fast air flow rate. The uniformity of the liner deposition is improved. The effective length of the liner deposition mandrel is increased, which increases the wire drawing length of a single mandrel. The working efficiency and the equipment utilization ratio are improved.

Description

Technical field [0001] The invention relates to a manufacturing method of a large-diameter optical fiber core rod, in particular to a PCVD manufacturing method of a large-diameter optical fiber core rod. Background technique [0002] PCVD, or in-tube plasma chemical vapor deposition, is one of the main processes for processing optical fiber preforms. The existing PCVD core rod manufacturing process has the following problems: [0003] 1. The inner and outer diameters of the liner used to make the mandrel are small, usually the inner diameter is less than or equal to 27 mm, and the outer diameter is less than or equal to 31 mm. During the deposition of the liner, the inner diameter of the liner increases with the increase of the deposition layer Gradually shrinking, the gas flow rate in the tube gradually increases; when the inner diameter of the liner tube is close to 20 mm, the plasma becomes very unstable due to the too fast gas flow rate, and the deposition effect is very poor...

AI Technical Summary

Problems solved by technology

[0003] 1. The inner and outer diameters of the liner used to make the mandrel are small, usually the inner diameter is less than or equal to 27 mm, and the outer diameter is less than or equal to 31 mm. During the deposition process of the liner, the inner diameter of the liner increases with the increase of the deposition layer When the inner diameter of the liner tube is close to 20 mm, the plasma becomes very unstable due to too fast gas flow rate, and the deposition effect is poor, so it is impossible to deposit a thicker deposition layer, and the deposition shrinks. The maximum diameter of the core in the solid mandrel behind the rod is within 19 mm, which greatly limits the drawing length of a single mandrel and affects the efficiency of optical fiber processing;

[0004] 2. The deposition time of the liner is long, and more dust generated during the deposition process will easily block the end of the deposition tube, resulting in deposition failure;

[0005] 3. When depositing in a liner with a small inner diameter, the uniformity of both ends of the mandrel is poor, the length of the effective rod is short, and there is a lot of waste;

[0006] 4. Due to the limitation of the gas flow rate in the tube, a higher deposition rate cannot be achieved, generally within 2.5 g / min, and the processing efficiency is low