Device and method for preparing optical fiber prefabricated bar base material by VAD

Abstract

The invention relates to a device and method for preparing an optical fiber prefabricated bar base material by VAD, wherein the device includes a reaction chamber for deposition and a rotating liftingsuspending rod extending into an inner cavity of the reaction chamber. A part, corresponding to the lower side of a to-be-deposited glass target bar, below the inner cavity of the deposition chamberis provided with a core layer spray lamp and a cladding layer spray lamp at intervals; the core layer spray lamp and the cladding layer spray lamp are connected with a core layer raw material controlsystem and a cladding layer raw material control system respectively; parts, corresponding to the deposition lower end face of the core layer, of two opposite sides of the exterior of the deposition cavity are provided with a laser emitting end and a laser receiving end respectively, and a core layer laser detection system is constructed. The device is characterized in that the core layer raw material control system and the core layer laser detection system are connected with a PLC, a PID closed-loop adjusting system between the flow rate of a core layer spray lamp raw material and the laser detection received value is formed, and a real-time feedback control is formed. The device has the advantages of simple structure, clear control logic, direct and rapid feedback, stable and reliable deposition performance, stable powder bar cross sections, and uniform core diameter and outer diameter, thereby improving production stability and product quality.

Description

technical field [0001] The invention relates to a device and method for preparing an optical fiber preform rod base material by VAD (axial external vapor deposition method), and belongs to the technical field of optical fiber manufacturing. Background technique [0002] In the process of manufacturing optical fiber preform base material, VAD (Vapour Axial Deposition) process is considered to reduce the production cost of optical fiber preform base material due to many factors such as high deposition rate, relatively low requirements for raw material purity, and suitable for large-scale production. main technical means. However, the VAD process technology itself is relatively complicated, and the center part of the powder rod produced by it is the most critical center part for laser transmission, because the cross-sectional shape of the core, the size of the core, and the uniformity of the core in the axial direction, etc. It directly determines the transmission performance ...

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Problems solved by technology

[0004] Chinese patent CN104355532A uses a laser to measure the diameter of the bottom end of the core layer of the powder rod, the diameter of the core layer, the diameter of the cladding deposition end surface and the diameter of the distal end of the outer cladding, and controls the deposited powder rod by controlling the parameters to adjust the flow rate of the raw material and the speed of the lifting chuck The parameters are qualified, and the target rod lifting judgment is determined by the comparison between the diameter of the bottom end of the powder rod and the preset shape. In the actual production process, the actual measurement height error of the bottom end of the core layer is relatively large, resulting in unreliable lifting, and this The control method has many measured values, and the logic judgment is complex, which is prone to logic confusion and crossover, resulting in unstable growth, and the cross-section of the mandrel made of the powder rod after sintering will have large fluctuations

[0005] U.S. Patent US6834516 uses a pyrometer to measure the temperature at the end of the preform powder rod for control, but the temperature measurement deviates from the actual value and is easily affected by the air flow in the cavity, which makes the measurement value problematic in terms of accuracy, and eventually Causes the product to be unstable throughout the production process, increasing the failure rate of the product

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