Abstract: A method of manufacturing an optical fiber, the method including mounting a glass sleeve in a selective etching apparatus. The sleeve comprising one or more axial through-holes, and the etching apparatus comprising a first end cap with a central aperture disposed therethrough, the first end cap being attached to a first surface of the sleeve. The method further including exposing the sleeve to an acid solution such that a first portion of the first surface is exposed to the acid solution and a second portion of the first surface is not exposed to the acid solution. The first portion being adjacent to the central aperture when the sleeve is mounted in the selective etching apparatus, and the second portion being covered by the first end cap when the sleeve is mounted in the selective etching apparatus.