Method for activating inner surface of substrate tube, optical fiber preform and optical fiber, and manufacturing method

Abstract

The present invention relates to a method for activating the inner surface of a substrate tube, as well as an optical fiber preform and an optical fiber and a manufacturing method. A method of activating the inner surface of a substrate tube used in the manufacture of an optical fiber preform by plasma etching with a fluorine-containing etching gas, the plasma etching comprising: supplying a supply flow of gas to the central cavity of the substrate tube, the supply flow comprising a main gas flow and fluorine-containing etching gas flow; using electromagnetic radiation to introduce plasma into at least a portion of the substrate tube to create a plasma region in the central cavity of the substrate tube; making the plasma region longitudinally located in the substrate tube Move back and forth in length between the reversing point near the supply side and the reversing point near the discharge side, where each back and forth movement is called a stroke, between the reversing point where the plasma region exists near the supply side and the reversing point located near the supply side A flow of fluorine-containing etching gas is provided between a predetermined axial position between the reversing point near the exhaust side and the reversing point near the discharge side.

Description

Technical field [0001] The present invention relates to a method for activating an inner surface of a base tube used in the fabrication of a fiber preform. The invention also relates to a base tube obtained by this method. Background technique [0002] One of the methods of fabricating fibers comprises depositing a plurality of thin films or multilayer glass (e.g., glass layers) on the inner surface of the (hollow) base tube. Subsequently, the base tube is radially contracted to form a fiber core, wherein the sleeve is selectively loaded or covered with the core rod to form an optical fiber preform that can be pulled into an optical fiber. [0003] The base tube can be considered to have an outer surface (in other words, the outer surface of the wall of the base tube) and the inner surface (in other words, the inner surface of the wall of the base tube). The inner surface of the base tube is in contact with a cavity present in the inside of the base tube. In an embodiment, the sh...

AI Technical Summary

Problems solved by technology

While very efficient, the process not only consumes additional time (typically 10 minutes), but also consumes additional glass-forming material; furthermore, it is quite complex, thus potentially introducing errors and thus reducing yield

Furthermore, this method is not very suitable for fluorine-doped substrate tubes, which are relatively soft and tend to increase the final out-of-roundness by utilizing this filling and sanding process