Purified quartz powder modified for cladding optic fiber cable

Abstract

A highly purified quartz powder having a low level of naturally occurring lithium modified for cladding a fiber optic cable, said modified quartz powder having an increased total amount of lithium in solid solution in said powder, said increased total amount being in the range of more than 0.50 ppm and less than 1.00 ppm and a method of modifying an highly purified quartz powder to make the same.

It is claimed: 
     
         1 . An highly purified quartz powder having a low level of naturally occurring lithium modified for cladding a fiber optic cable, said modified quartz powder having an increased total amount of lithium in solid solution in said powder, said increased total amount being in the range of more than 0.50 ppm and less than 1.00 ppm. 
     
     
         2 . The modified high purity quartz powder as defined in  claim 1  wherein said increased total amount of lithium in said modified powder is in the range of 0.6 to 0.8 ppm. 
     
     
         3 . The modified highly purity quartz powder as defined in  claim 1  wherein said increased total amount of lithium in said modified powder is in the range of 0.60 to 0.85 ppm. 
     
     
         4 . The modified highly purified quartz powder as defined in  claim 1  wherein said increased total amount of lithium in said modified powder is about 0.6 ppm. 
     
     
         5 . The modified highly purified quartz powder as defined in  claim 1  has a maximum particle size D99 in the range of 200-400 microns and a minimum particle size D5 in the range of 50-70 microns. 
     
     
         6 . The modified highly purified quartz powder as defined in  claim 1  wherein said low level of naturally occurring lithium of said modified powder is less than 0.3 ppm lithium. 
     
     
         7 . The modified highly purified quartz powder as defined in  claim 1  wherein said low level of naturally occurring lithium of said modified powder is about 0.2 ppm. 
     
     
         8 . The modified highly purified quartz powder as defined in  claim 1 , which modified highly purified quartz powder results in an attenuation less than 0.187 dB/km when used for cladding of a fiber optic cable. 
     
     
         9 . The modified highly purified quartz powder as defined in  claim 1 , which modified highly purified quartz powder results in an attenuation less than 0.184 dB/km when used for cladding of a fiber optic cable. 
     
     
         10 . A method of modifying an highly purified quartz powder having a low level of naturally occurring lithium for use in cladding a fiber optic cable, said method comprising:
 a) forming a solution of a lithium doping agent;   b) blending said highly purified quartz powder with said doping solution to provide a blended mass with a given level of lithium comprising lithium of said doping solution coated onto said highly purified quartz powder and the low level of naturally occurring lithium of said highly purified quartz powder;   c) gassing said blended mass with a gas heated to a temperature of at least 1000° C. for a time to dope said highly purified powder with lithium in said doping solution; and,   d) controlling the amount of lithium from said doping solution that is doped into said highly purified quartz powder so the total lithium in solid solution in said modified highly purified quartz powder is at a final level of 0.50-1.00 ppm.   
     
     
         11 . The method as defined in  claim 10  wherein said lithium amount controlling operation includes adjusting said given level of lithium in said blended mass. 
     
     
         12 . The method as defined in  claim 10  wherein said lithium amount controlling operation includes the temperature of said gassing operation. 
     
     
         13 . The method as defined  claim 10  wherein said lithium amount controlling operation includes the time of said gassing operation. 
     
     
         14 . The method as defined in  claim 10  wherein said final level is in the range of more than 0.50 ppm and less than 1.00 ppm. 
     
     
         15 . The method as defined in  claim 10  wherein said final level is in the range of 0.6 to 0.8 ppm. 
     
     
         16 . The method as defined in  claim 10  wherein said final level is in the range of 0.60 to 0.85 ppm. 
     
     
         17 . The method defined in  claim 10  wherein said final level is about 0.60 ppm. 
     
     
         18 . The method as defined in  claim 10  wherein said given level of lithium in said blended mass is in the range of 0.80 to 2.0 ppm. 
     
     
         19 . The method as defined in  claim 10  wherein said given level of lithium in said blended mass is in the range of 0.80 to 1.0 ppm. 
     
     
         20 . The method as defined in  claim 10  wherein said gassing temperature is in the range of 1200-1300° C. 
     
     
         21 . The method as defined in  claim 10  including drying said blended mass at a temperature of 80-100° C. before gassing of said blended mass. 
     
     
         22 . The method as defined in  claim 10  wherein said blended mass has a moisture content of 2-5 percent. 
     
     
         23 . The method as defined in  claim 10  wherein said lithium doping agent is a lithium salt. 
     
     
         24 . The method as defined in  claim 23  wherein said lithium doping agent is LiNO 3 . 
     
     
         25 . The method as defined in  claim 10  wherein the lithium doping agent includes aluminum to increase the portion of lithium from said blended mass converted to solid solution doped into said highly purified powder during said gassing operation. 
     
     
         26 . The method as defined in  claim 25  wherein said lithium doping agent is LiAlO 2 . 
     
     
         27 . The method as defined in  claim 25  wherein said lithium doping agent is a lithium salt combined with an aluminum salt. 
     
     
         28 . The method as defined in  claim 27  wherein said aluminum salt is Al(NO 3 ) 3 .