Specialty Optical Fibers Handbook

into a rotating tube, which is mounted in a glass working lathe and heated

by a traversing oxy-hydrogen torch. Homogeneous gas phase reaction occurs

in the hot zone created by the torch to produce amorphous particles, which

deposit downstream of the hot zone. The heat from the moving torch sinters

this deposit to form a pure glass layer. Typical torch temperatures are suffi-

ciently high to sinter the deposited material, but not so high as to deform

the substrate tube. The torch is traversed repeatedly to build up, layer by

layer, the core or cladding. Composition of the individual layers is varied

between traversals to build the desired fiber index structure. Typically, 30 to

100 layers are deposited to make either single-mode or graded index multimode ...