Bell Telephone Laboratories

At&t Bell Laboratories

American Telephone & Telegraph Co., At&t Bell Laboratories

Robert L Barns

Edwin Arthur Chandross

Louis Thomas Manzione

Daniel L Flamm

Larry F Thompson

Arthur D Pearson

Suzanne R Nagel

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.

Process for making optical fibers

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.

Optical fiber fabrication process

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.

Purification process for compounds useful in optical fiber manufacture

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.

Removal of --OH impurities from fiber optic precursor materials

z-face quartz of good quality suitable for piezoelectric applications can be grown at rates near 35 mil/da at p-T conditions easily accessible in commercial autoclaves. The growth conditions are predictable from previous systematic studies of growth rate. Cracking of grown crystals either during growth or in crystal processing can be severe and can account for as much as 15-50% yield loss. However, much of this loss can be reduced by carefully screening seeds for strain using the new polariscopic technique of the invention. Strain (and cracking) are severe with growth on highly strained seeds and at high growth rates. Carefully choosing seeds reduces the strain in the grown material for a given growth rate.

Growing community of inventors

Berkeley Heights, NJ, United States of America

Robert L Barns