Low attenuation optical fiber

Abstract

An optical fiber with low attenuation is provided. The fiber is produced under conditions that reduce fictive temperature. Processing includes maintaining the fiber at temperatures at or near the glass transition temperature (T g ) for an extended period of time. For silica-based fibers, the preferred temperatures are temperatures between 1000° C. and 1700° C. The extended residence times are achieved in a continuous fiber manufacturing process by increasing the path length of the fiber through a processing region maintained at temperatures between 1000° C. and 1700° C. The increased path length is achieved by including one or more fluid bearing devices in the processing region. The extended residence time in the processing region allows the structure of the glass fiber to relax more completely and to more closely approach the equilibrium state. The more relaxed glass structure leads to a lower fictive temperature and provides fibers with lower attenuation.

What is claimed is: 
     
         1 . An optical fiber produced by a method comprising:
 directing an optical fiber in a first direction of conveyance, said optical fiber having a first temperature along said first direction of conveyance, said first temperature being between 1000° C. and 1700° C.; and   redirecting said optical fiber from said first direction of conveyance to a second direction of conveyance using a series of at least two heated fluid bearing devices, said optical fiber having a second temperature upon said redirecting to said second direction of conveyance, said second temperature being between 1000° C. and 1700° C.;   wherein said optical fiber is maintained at said first temperature and said second temperature for a combined time greater than 0.5 sec; and   wherein a temperature of each one of said at least two heated fluid bearing devices is at least 500° C.   
     
     
         2 . The optical fiber of  claim 1 , wherein said optical fiber has an attenuation less than 0.17 dB/km at 1550 nm. 
     
     
         3 . The optical fiber of  claim 1 , wherein said optical fiber has an attenuation less than 0.15 dB/km at 1550 nm. 
     
     
         4 . The optical fiber of  claim 1 , wherein said optical fiber has an attenuation less than 0.14 dB/km at 1550 nm. 
     
     
         5 . The optical fiber of  claim 1 , wherein said optical fiber has a fictive temperature less than 1450° C. 
     
     
         6 . The optical fiber of  claim 1 , wherein said optical fiber has a fictive temperature less than 1400° C. 
     
     
         7 . The optical fiber of  claim 1 , wherein said optical fiber has a fictive temperature less than 1350° C. 
     
     
         8 . The optical fiber of  claim 1 , wherein said optical fiber has a fictive temperature less than 1300° C.