After consolidation, preforms made by the vapor axial deposition (VAD) process are routinely stretched into smaller diameter rods so that further cladding can be added. Stretching can be accomplished on a glass lathe by passing the torch along the length of the preform while applying tension to it through translation of the tailstock. The effect of this process on the preform, other than to reduce its diameter, has not been determined. Careful examination of the preform layer structure after stretching shows that it changes shape. Such distortion, i.e., relative displacement of initially adjacent points, is particularly obvious in multimode preforms, as shown in Fig. 1 where a pure silica marker layer has been deliberately deposited.
© 1986 Optical Society of AmericaPDF Article