Apparatus and method of manufacturing optical waveguides

Abstract

An apparatus and method of manufacturing optical waveguides that comprises non-optically measuring the average temperature of a moving optical waveguide fiber as it exits a heated draw furnace using a temperature device. The device comprises an enclosed chamber that has a plurality of differential thermopiles secured to the inside surface, and a cooling system that substantially maintains a reference surface temperature of one end of each of the thermopiles. Each of the thermopiles are serially interconnected, whereby, in response to a maximum amount of radiant energy absorbed, the thermopiles generate an output signal. The output signal is substantially proportional to the maximum amount of radiant energy absorbed by the thermopiles, which in turn is substantially proportional to the fourth power of the average temperature of the moving optical waveguide fiber within the chamber.

What is claimed is:  
     
         1 . A method of measuring the temperature T f  of an optical waveguide fiber being drawn from a heated optical waveguide preform in a draw furnace, said method comprising the steps of: 
 passing said optical waveguide fiber through a chamber, said chamber being positioned downstream from said draw furnace;    maintaining a reference surface temperature T s  of one surface of each of a plurality of differential thermopiles, each of said differential thermopiles being fixed to an inner surface of said chamber; and    generating an aggregate output signal representative of the radiant energy absorbed by said differential thermopiles within said chamber.    
     
     
         2 . The method of  claim 1 , wherein said passing step includes: 
 providing said chamber having a plurality of side walls and a central channel that traverses said chamber from a top wall to a bottom wall.    
     
     
         3 . The method of  claim 2 , further comprising the steps of: 
 serially interconnecting a plurality of differential thermocouple pairs to form one of said plurality of differential thermopiles; and    securing said one of said plurality of differential thermopiles to an inner surface of each of said side walls of said chamber.    
     
     
         4 . The method of  claim 3 , wherein a first thermocouple of each of said differential thermocouple pairs is thermally isolated from a second thermocouple, said second thermocouple being in thermal contact with said side walls of said chamber.  
     
     
         5 . The method of  claim 3 , further comprising the step of: 
 serially interconnecting each of said differential thermopiles in said chamber to a voltmeter.    
     
     
         6 . The method of  claim 5 , further comprising the step of: 
 providing a cooling system that is in thermal contact with said side walls of said chamber, said cooling system being adapted to substantially maintain a reference surface temperature T s  of each of said second thermocouples of said differential thermopiles.    
     
     
         7 . The method of  claim 6 , wherein said providing step includes: 
 providing within said side walls of said chamber a plurality of channels that are adapted to receive a coolant having an approximate temperature T s .    
     
     
         8 . The method of  claim 7 , wherein said amount of radiant energy absorbed by said differential thermopiles is substantially proportional to the fourth power of the average optical waveguide fiber temperature T f  of a length of optical waveguide fiber within said chamber.  
     
     
         9 . The method of  claim 8 , wherein said chamber is made of aluminum.  
     
     
         10 . A method of manufacturing an optical waveguide fiber, said method comprising the steps of: 
 providing an optical waveguide preform;    heating said optical waveguide preform to a draw temperature;    drawing an optical waveguide fiber from said heated optical waveguide preform;    providing a heat flux chamber having an optical waveguide fiber entrance and an optical waveguide fiber exit;    passing said drawn optical waveguide fiber through said entrance and out said exit; and    non-optically measuring the heat flux radiated by said optical waveguide fiber within said chamber.    
     
     
         11 . The method of  claim 10 , wherein said non-optically measuring step includes: 
 serially interconnecting an array of heat flux sensors to an inner surface of a plurality of side walls of said heat flux chamber; and    providing a cooling system that is in thermal contact with said plurality of side walls of said heat flux chamber and is adapted to substantially maintain a reference surface temperature of each of said heat flux sensors.    
     
     
         12 . The method of  claim 10 , further comprising adjusting said draw temperature based on a measured heat flux of said length of optical waveguide fiber within said chamber.  
     
     
         13 . The method of  claim 12 , wherein said measured heat flux is proportional to the fourth power of an average temperature of said length of optical waveguide fiber within said chamber.  
     
     
         14 . An optical waveguide temperature device for non-optically measuring an average temperature T f  of a length of optical waveguide fiber being drawn from a heated optical waveguide preform in a draw furnace heated to a draw temperature, said device comprising: 
 a thermally isolated chamber having a plurality of side walls and a central channel that traverses said chamber from a top wall to a bottom wall, said chamber being adapted to receive through said central channel said length of optical waveguide fiber being drawn;    a plurality of differential thermopiles secured to the inside surface of said side walls of said chamber, a first surface of each of said differential thermopiles being thermally isolated from a second surface, said first surface of each of said differential thermopiles faces said central channel and has a dark absorptive surface, said first surface of each of said differential thermopiles being exposed to said heat flux, said second surface being in thermal contact with said side walls of said chamber, said second surface of said differential thermopiles having a reference surface temperature of about T s ; and    a cooling system in thermal contact with said side walls of said chamber, said cooling system being adapted to substantially maintain said reference surface temperature T s  of said side walls of said chamber.    
     
     
         15 . The temperature device of  claim 14 , wherein said cooling system includes a network of channels built into said side walls of said chamber, said network of channels being adapted to receive a coolant from an external chiller that substantially maintains said reference surface temperature T s  of each of said differential thermopiles.  
     
     
         16 . The temperature device of  claim 14 , wherein each of said differential thermopiles includes a plurality of differential thermocouple pairs, a first thermocouple of each of said differential thermocouple pairs being thermally isolated from a second thermocouple and in thermal contact with said side walls of said chamber, said second thermocouple having a reference surface temperature of about T s .  
     
     
         17 . The temperature device of  claim 14 , wherein each of said differential thermopiles generates an output signal that is substantially proportional to an amount of radiant energy absorbed from said length of optical waveguide fiber within said chamber.  
     
     
         18 . The temperature device of  claim 14 , further comprising a draw furnace controller for maintaining said draw temperature of said draw furnace.  
     
     
         19 . The temperature device of  claim 14 , wherein said draw furnace is in alignment with and upstream from said chamber.  
     
     
         20 . The temperature device of  claim 19 , wherein said temperature T f  of said length of optical waveguide fiber is used to control said draw temperature of said draw furnace.  
     
     
         21 . The temperature device of  claim 20 , wherein a maximum amount of radiant energy absorbed by said differential thermopiles is substantially proportional to the fourth power of said average optical waveguide fiber temperature T f  of said length of optical waveguide fiber within said chamber.  
     
     
         22 . The temperature device of  claim 21 , wherein said chamber is made of a metal having a thermal conductivity in the range of 170 W/m.K to 237 W/m.K.  
     
     
         23 . The temperature device of  claim 22 , wherein each of said side walls of said chamber comprises a serially interconnected array of at least 1000 thermocouple pairs.  
     
     
         24 . The temperature device of  claim 23 , wherein each of said side walls of said chamber comprises a serially interconnected array of approximately 1600 thermocouple pairs.  
     
     
         25 . The temperature device of  claim 24 , wherein said network of channels comprises a plurality of flexible tubes that are adapted for connection to said external chiller.  
     
     
         26 . The temperature device of  claim 25 , wherein said coolant received into said channels is substantially maintained at said temperature T s  by said external chiller.  
     
     
         27 . The temperature device of  claim 26 , further comprising an optical waveguide fiber coating apparatus in alignment with and downstream from said chamber.  
     
     
         28 . The temperature device of  claim 27 , wherein each of said differential thermopiles is serially interconnected to an output signal measuring device.  
     
     
         29 . The temperature device of  claim 28 , wherein said metal is aluminum.  
     
     
         30 . An optical waveguide fiber manufacturing device, said device comprising: 
 a draw furnace heated to a draw temperature;    an optical waveguide preform positioned within said draw furnace, said optical waveguide preform being heated to said draw temperature;    a temperature monitor for non-contact measurement of an average temperature T f  of an optical waveguide fiber being drawn from said heated optical waveguide preform, said temperature monitor being in alignment with said draw furnace and including: 
 a thermally isolated chamber having a plurality of side walls and a central channel that traverses said chamber from a top wall to a bottom wall, said chamber being positioned downstream from said draw furnace, said chamber being adapted to receive through said central channel said optical waveguide fiber being drawn from said optical waveguide preform, said chamber having: 
 a plurality of heat flux sensors adapted to measure an amount of heat flux radiated by said optical waveguide fiber within said chamber, each of said heat flux sensors being fixed securely to an inner surface of said side walls of said chamber; and  
 a cooling system in thermal contact with said side walls of said chamber, said cooling system being adapted to substantially maintain a reference surface temperature T s  of each of said heat flux sensors.  
 
   
     
     
         31 . The device of  claim 30 , further comprising a draw furnace controller for maintaining said draw temperature, said draw furnace controller including an input from said temperature monitor.  
     
     
         32 . The device of  claim 30 , wherein said temperature T f  of said optical waveguide fiber is used to control said draw temperature of said draw furnace.  
     
     
         33 . The device of  claim 30 , wherein each of said heat flux sensors comprises a plurality of differential thermocouple pairs, wherein said amount of heat flux radiated by said optical waveguide fiber within said chamber causes a temperature gradient to develop across each of said differential thermocouple pairs.  
     
     
         34 . The device of  claim 30 , wherein a first thermocouple of each of said differential thermocouple pairs is thermally isolated from a second thermocouple, said second thermocouple being in thermal contact with said inner surface of said side walls of said chamber.  
     
     
         35 . The device of  claim 30 , wherein said cooling system comprises a plurality of flexible channels, each of said channels being adapted to receive a coolant whose temperature is substantially maintained at said reference surface temperature T s  by an external chiller.  
     
     
         36 . The device of  claim 35 , wherein said second thermocouple of each of said differential thermocouple pairs is in thermal contact with at least one of said channels, and wherein said coolant received through said channels substantially maintains said reference surface temperature T s  of each of said second thermocouples.  
     
     
         37 . The device of  claim 36 , wherein each of said differential thermocouple pairs is serially interconnected to form a differential thermopile.  
     
     
         38 . The device of  claim 37 , wherein said chamber has four side walls, said differential thermopile being fixed to each of said side walls, wherein a surface of each of said differential thermopiles facing said central channel of said chamber has a dark absorptive surface.  
     
     
         39 . The device of  claim 38 , wherein each of said side walls comprises at least 1000 differential thermocouple pairs.  
     
     
         40 . The device of  claim 39 , wherein said differential thermopiles are serially interconnected to generate an aggregate output signal representative of a maximum amount of radiant energy absorbed from said optical waveguide fiber within said chamber.  
     
     
         41 . The device of  claim 40 , wherein said aggregate signal is substantially proportional to said average optical waveguide fiber temperature T f  of said length of optical waveguide fiber within said chamber.  
     
     
         42 . The device of  claim 41 , wherein said maximum amount of radiant energy absorbed from said optical waveguide fiber within said chamber is substantially proportional to the fourth power of said average temperature T f  of said length of optical waveguide fiber within said chamber.  
     
     
         43 . The device of  claim 42 , wherein said chamber is made of a metal having a thermal conductivity in the range of 170 W/m.K to 237 W/m.K.  
     
     
         44 . The device of  claim 43 , further comprising a locking mechanism that opens and closes said chamber for receiving said optical waveguide fiber being drawn from said optical waveguide preform.  
     
     
         45 . The device of  claim 44 , further comprising an optical waveguide fiber coating apparatus in alignment with and downstream from each of said draw furnace and said temperature monitor.  
     
     
         46 . The device of  claim 45 , further comprising a second temperature monitor in alignment with and downstream from said temperature monitor.