Doping device for optical fiber preform

Abstract

The invention provides a doping device for an optical fiber preform. On modified chemical vapor deposition equipment, a required clad material is deposited on an inner wall of a reaction tube by using an improved MCVD method; a gas phase and liquid phase composite doping device is employed to carry out uniform doping of active doping ions and a co-doped agent. For the gas phase doping, a simple-structured and low-cost heater is employed for direct heating; and a dopant is constantly heated by the heater, and is introduced by current-carrying oxygen for doping after vaporization. For the liquid phase doping, a micropore jet doping device is used to carry out direct online doping of a doping solution through an injection device. The composite doping device is used to carry out preparation of a rare earth doped preform, so as to realize synchronous deposition and vitrification of the rare earth doping ions, the co-doped agent and quartz base materials comprising silica and germanium dioxide, avoid dependence on the deposition loose pore structure layer, and increase flexibility of the concentration and the variety of the doping ions.

Description

technical field [0001] The invention belongs to optical fiber preparation technology, and relates to a doping device for an optical fiber preform, in particular to a doping device for preparing a rare earth doped preform with high doping efficiency and high doping uniformity. Background technique [0002] Rare-earth-doped active optical fiber mainly refers to optical fiber doped with rare-earth ions with atomic number 57-71 in the matrix. The matrix materials include phosphate glass, tellurate glass, silicate glass, etc. The most mature and widely used is the silica glass-doped rare-earth optical fiber based on silica glass. The main reason is that the active optical fiber is used as the gain medium of the optical amplifier in the field of optical communication, which requires good compatibility with the silica communication optical fiber. The fiber laser gain medium requires a large damage threshold, and the thermal performance of the quartz matrix is ​​good under the condi...

AI Technical Summary

Problems solved by technology

[0006] In the preparation process of active optical fiber, the following problems will exist in the above preparation method and doping method: (1) the preform needs to be removed from the lathe by the solution method to soak the preform, and then reinstalled on the lathe after soaking , this will often bring impurities and cause the background loss to be unable to be reduced. Chinese patent document CN 1996070A proposes an online doping method, which overcomes the link of removing the preform for doping and causing pollution, but it is still the loose pore-like Solution doping is carried out after the layer deposition is completed, which is highly dependent on the structure of the loose porous layer

(2) Soak the rare earth solution after depositing the loose porous layer by the vapor phase method. The quality requirements for the loose porous layer are very strict. If the loose porous layer is too thin, the doping concentration is small, and the loose porous layer is too thick and easy to fall off. In actual operation, uneven doping often occurs. During sintering, since rare earth ions and co-doped ions are concentrated in the center of the fiber core, clusters or crystallites of doped ions are prone to appear when forming rods, making the distribution of dopant substances uneven

(3) In addition, by depositing the outside or inside of the preform into a loose pore-like structure, and using liquid phase doping such as solution soaking or spraying, it is very difficult to control the uniformity of the pores in the radial direction, and its small changes lead to rare earth and co-doping Ion concentration varies significantly in the radial distribution and is difficult to control

(4) The doping of rare earth ions by the gas phase method has improved the uniformity, but because the saturated vapor pressure of rare earth ions is too high, it is very difficult to gasify rare earth ion equipment and control. The current D ND technology is mastered by NLIGHT in the United States In the company

At the same time, with the development of technology at any time, the types of rare earth ion doping and co-dopants are also increasing. To achieve complete gas phase doping requires each raw material to have its own vaporization device, which is difficult to achieve.

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