Abstract: A method of making 1.times.2 or 2.times.2 overclad couplers, switches and the like such that the process is more reproducible and loss characteristics are improved. Such couplers are typically made by inserting the stripped portions of two active optical fibers into a tube, heating the tube midregion to collapse it onto the fibers and stretching the central portion of the collapsed midregion to achieve the desired coupling characteristics. The improvement involves the insertion of one or two spacer fibers into the tube bore along with the active fibers to take up empty space that had been present in tube bore and to prevent an active fiber from sagging and crossing over the other fiber when the tube is heated during the tube collapse step.

Abstract: A method of producing a fused silica product comprising introducing a silicon-containing, organometallic compound into a flame to form molten silica particles, and collecting the molten silica particles in a furnace having a crown and cup such that a fused silica product is obtained, wherein at least the furnace crown is formed from a porous, fired, zircon refractory having a sodium ion content of less than 30 ppm. The fused silica product produced by the method has a sodium ion contamination level below 100 parts per billion.

Abstract: A fired, porous, zircon refractory body consisting essentially of zircon and having a sodium ion content, as an impurity, of less than 30 ppm. A furnace for making fused silica constructed with a crown and cup of such zircon refractory, and a method of making fused silica using such furnace.