Method for dehydrating and sintering porous base material for optical fiber

Abstract

A dehydration-sintering furnace includes a core tube configured to dehydrate and sinter a porous base material in fabrication of an optical fiber and having an outlet configured to discharge a vapor. The furnace includes a pressure-variation damper connected to the outlet of the core tube. The furnace includes a trap between the core tube and the pressure-variation damper for collecting the vapor.

1 . A method for dehydrating and sintering a porous base material for an optical fiber, comprising:
 absorbing a pressure variation in a core tube in a dehydration and sinter of the porous base material therein, by discharging a gas from the core tube when a pressure therein is high and returning the discharged gas thereinto when the pressure therein is low; and   trapping vapor included in the discharged gas from the core tube by liquefying the vapor in the absorption of the pressure variation.   
     
     
         2 . The method according to  claim 1 , wherein the absorption of the pressure variation is performed by a pressure-variation damper connected to the core tube, the trap of the vapor by the liquefaction thereof is performed by a trap tank located between the core tube and the pressure-variation damper. 
     
     
         3 . The method according to  claim 2 , further comprising draining a liquid trapped in the trap tank. 
     
     
         4 . The method according to  claim 2 , wherein the trap of the vapor is performed by cooling the trap tank. 
     
     
         5 . The method according to  claim 2 , wherein the trap tank is made of a material which is not corroded by the vapor 
     
     
         6 . The method according to  claim 5 , wherein the material of the trap tank is a glass or resin material. 
     
     
         7 . The method according to  claim 6 , wherein the resin material is polytetrafluoroethylene (PTFE) or polyvinyl chloride (PVC). 
     
     
         8 . The method according to  claim 4 , wherein, the cooling of the trap tank is performed by heat exchange between the trap tank and a coolant. 
     
     
         9 . The method according to  claim 4 , wherein the cooling of the trap tank is performed by blowing the trap tank. 
     
     
         10 . The method according to  claim 4 , wherein the cooling of the trap tank is performed by a refrigeration unit which houses the trap tank. 
     
     
         11 . The method according to  claim 2 , wherein the trap tank has fins on an outer surface thereof, the fins being made of a material having a thermal conductivity which allows heat exchange between the air and the trap tank to cool the trap tank. 
     
     
         12 . A method for dehydrating and sintering a porous base material for an optical fiber, comprising:
 absorbing a pressure variation in a core tube in a dehydration and sinter of the porous base material therein, by discharging a gas from the core tube when a pressure therein is high and returning the discharged gas thereinto when the pressure therein is low; and   trapping vapor included in the discharged gas from the core tube by dehumidifying the vapor in the absorption of the pressure variation.   
     
     
         13 . The method according to  claim 12 , wherein the trap of the vapor by dehumidification is performed by a moisture absorbent. 
     
     
         14 . The method according to  claim 12 , wherein the absorbing the pressure variation is performed by a pressure-variation damper connected to the core tube, the trap of the vapor by dehumidification is performed by a moisture absorbent which is filled in a dehumidification container between the core tube and the pressure-variation damper. 
     
     
         15 . The method according to  claim 13 , wherein the moisture absorbent includes at least one of a silica gel and a charcoal.