Abstract: The extent of loss produced in fibers due to the presence of OH infrared absorption bands is significantly reduced through the use of specific expedients during, for example, the preform collapse procedure. In particular, during this procedure a carbon tetrahalide composition is employed to essentially prevent the presence of any residual hydrogen-containing entity from influencing the quality of the preform and thus from influencing the quality of the fiber ultimately produced.

Abstract: A method of forming optical fibers with minimal contamination from ambient air is disclosed. In the inventive method a gas stream is introduced into a rotating structure by means of a rotating seal. The rotating seal comprises a rotating member seated within a stationary member. Counterflowing gases are flowed through the clearance region between the rotating and stationary members to prevent seepage of ambient air into the gas stream.

Abstract: Silicon tetrachloride is processed to ultrahigh purity by subjecting it to a specific succession of purification steps. These steps include the photochlorination of the SiCl.sub.4 using a reactor that allows a long residence time for the SiCl.sub.4. After photochlorination, highly volatile products such as HCl are removed and the remaining impurities are then separated by a distillation technique.

Abstract: The presence of hydroxyl impurities (--OH) in optical fiber precursor materials produces optical losses in fibers made from the precursor material, as in the modified chemical vapor deposition process. Typical precursor materials include SiCl.sub.4, GeCl.sub.4, POCl.sub.3, and PCl.sub.3. Losses due to --OH impurities occur near various wavelengths of current interest for optical communications systems. Adding chlorine and PCl.sub.3 to impure SiCl.sub.4, GeCl.sub.4, or POCl.sub.3 reduces the amount of --OH impurities and produces POCl.sub.3 and HCl. The HCl may be readily removed, while the POCl.sub.3 is typically left in the material. Bromine may be used instead of chlorine, and PBr.sub.3 may be used instead of PCl.sub.3. In addition, --OH impurities in PCl.sub.3 may be removed by the addition of chlorine or bromine, with the resulting HCl or HBr typically being removed.