Method of fabricating optical fibres by solution-doping

Claim 1

A method of doping a core of a silica-based fiber preform, comprising depositing a soot layer, which will form said core of said silica-based optical fiber preform, inside a reaction tube supported by a lathe, and connected to at least one deposition reactant inlet conduit and at least one exhaust conduit, and then impregnating the deposited core soot layer contained inside said reaction tube supported by said lathe with a solution of a precursor of at least a first dopant which raises the refractive index of said layer without giving rise to a central dip of said index, said solution of a precursor of said first dopant being a solution in an anhydrous organic solvent, wherein after said layer deposition, (a) the reaction tube is disconnected from the at least one deposition reactant inlet conduit as well as from the at least one exhaust conduit for the deposition reaction volatile products; (b) at least a reaction product exhaust end of the reaction tube is sealed in a sealing operation, while an inert and anhydrous gas flow is maintained in said reaction tube during the sealing operation; (c) said solution is introduced into the reaction tube, without removing the tube from the lathe so that the solution covers the whole surface of the deposited layer and impregnation of the deposited layer occurs; and (d) once impregnation is over, the solution is caused to slowly flow out, at a uniform rate, from the reaction tube, which reaction tube is still mounted on the lathe.

Claim 2

A method of doping a core of a silica-based fiber preform, comprising depositing a soot layer, which will form said core of said silica-based optical fiber preform, inside a reaction tube supported by a lathe, and connected to at least one deposition reactant inlet conduit and at least one exhaust conduit, and then impregnating the deposited core soot layer contained inside said reaction tube supported by said lathe with a solution of a precursor of at least a first dopant which raises the refractive index of said layer without giving rise to a central dip of said index, said solution of a precursor of said first dopant being a solution in an anhydrous organic solvent, wherein after said layer deposition, (a) the reaction tube is disconnected from the at least one deposition reactant inlet conduit as well as from the at least one exhaust conduit for the deposition reaction volatile products; (b) at least a reaction product exhaust end of the reaction tube is sealed in a sealing operation, while an inert and anhydrous gas flow is maintained in said reaction tube during the sealing operation; (c) said solution is introduced into the reaction tube, without removing the tube from the lathe so that the solution covers the whole surface of the deposited layer and impregnation of the deposited layer occurs; and (d) once impregnation is over, the solution is caused to slowly flow out, at a uniform rate, from the reaction tube, which reaction tube is still mounted on the lathe.

Claim 13

A method of doping a core of a silica-based fiber preform, comprising depositing a soot layer, which will form said core of said silica-based optical fiber preform, inside a reaction tube supported by a lathe, and connected to at least one deposition reactant inlet conduit and at least one exhaust conduit, and then impregnating the deposited core soot layer contained inside said reaction tube supported by said lathe with a solution of a precursor of at least a first dopant which raises the refractive index of said layer without giving rise to a central dip of said index, said solution of a precursor of said first dopant being a solution in an anhydrous organic solvent, wherein after said layer deposition, (a) the reaction tube is disconnected from the at least one deposition reactant inlet conduit as well as from the at least one exhaust conduit for the deposition reaction volatile products; (b) at least a reaction product exhaust end of the reaction tube is sealed in a sealing operation, while an inert and anhydrous gas flow is maintained in said reaction tube during the sealing operation; (c) said solution is introduced into the reaction tube, without removing the tube from the lathe so that the solution covers the whole surface of the deposited layer and impregnation of the deposited layer occurs; and (d) once impregnation is over, the solution is caused to slowly flow out, at uniform rate, from the reaction tube, which reaction tube is still mounted on the lathe, a sealing of an exhaust end of the reaction tube being effected by a resilient membrane mounted on a conduit which is coaxial with the reaction tube and in which an overpressure is established.

Claim 14

A method of doping a core of a silica-based fiber preform, comprising depositing a soot layer, which will form said core of said silica-based optical fiber preform, inside a reaction tube supported by a lathe, and connected to at least one deposition reactant inlet conduit and at least one exhaust conduit, and then impregnating the deposited core soot layer contained inside said reaction tube supported by said lathe with a solution of a precursor of at least a first dopant which raises the refractive index of said layer without giving rise to a central dip of said index, said solution of a precursor of said first dopant being a solution in an anhydrous organic solvent, wherein after said layer deposition, (a) the reaction tube is disconnected from the at least one deposition reactant inlet conduit as well as from the at least one exhaust conduit for the deposition reaction volatile products; (b) at least a reaction product exhaust end of the reaction tube is sealed in a sealing operation, while an inert and anhydrous gas flow is maintained in said reaction tube during the sealing operation; (c) said solution is introduced into the reaction tube, without removing the tube from the lathe so that the solution covers the whole surface of the deposited layer and impregnation of the deposited layer occurs; and (d) once impregnation is over, the solution is caused to slowly flow out, at uniform rate, from the reaction tube, which reaction tube is still mounted on the lathe, a sealing of an exhaust end of the reaction tube being effected by a resilient membrane mounted on a conduit which is coaxial with the reaction tube and in which an overpressure is established.

Claim 15

A method of doping a core of a silica-based fiber preform, comprising depositing a soot layer, which will form said core of said silica-based optical fiber preform, inside a reaction tube supported by a lathe, and connected to at least one deposition reactant inlet conduit and at least one and then impregnating the deposited core soot layer contained inside said reaction tube supported by said lather with a solution of a precursor of at least a first dopant which raises the refractive index of said layer without giving rise to a central dip of said index, said solution of a precursor of said first dopant being a solution in an anhydrous organic solvent, wherein after said layer deposition, (a) the reaction tube is disconnected from the at least one deposition reactant inlet conduit as well as from the at least one exhaust conduit for the deposition reaction volatile products; (b) at least a reaction product exhaust end of the reaction tube is sealed in a sealing operation, while an inert and anhydrous gas flow is maintained in said reaction tube during the sealing operation; (c) said solution is introduced into the reaction tube, without removing the tube from the lathe so that the solution covers the whole surface of the deposited layer and impregnation of the deposited layer occurs; and (d) once impregnation is over, the solution is caused to slowly flow out, at uniform rate, from the reaction tube, which reaction tube is still mounted on the lathe the solution being introduced after the reaction tube is disposed in an inclined position with an exhaust end down, via a further tube penetrating inside the reaction tube through said exhaust end, and is removed through said further tube, by gravity or by sucking, the exhaust end of the reaction tube being sealed by means of an inflatable elastomeric toroidal member placed between the internal surface of the reaction tube and the external surface of said further tube.

Claim 16

A method of doping a core of a silica-based fiber preform, comprising depositing a soot layer, which will form said core of said silica-based optical fiber preform, inside a reaction tube supported by a lathe, and connected to at least one deposition reactant inlet conduit and at least one and then impregnating the deposited core soot layer contained inside said reaction tube supported by said lather with a solution of a precursor of at least a first dopant which raises the refractive index of said layer without giving rise to a central dip of said index, said solution of a precursor of said first dopant being a solution in an anhydrous organic solvent, wherein after said layer deposition, (a) the reaction tube is disconnected from the at least one deposition reactant inlet conduit as well as from the at least one exhaust conduit for the deposition reaction volatile products; (b) at least a reaction product exhaust end of the reaction tube is sealed in a sealing operation, while an inert and anhydrous gas flow is maintained in said reaction tube during the sealing operation; (c) said solution is introduced into the reaction tube, without removing the tube from the lathe so that the solution covers the whole surface of the deposited layer and impregnation of the deposited layer occurs; and (d) once impregnation is over, the solution is caused to slowly flow out, at uniform rate, from the reaction tube, which reaction tube is still mounted on the lathe the solution being introduced after the reaction tube is disposed in an inclined position with an exhaust end down, via a further tube penetrating inside the reaction tube through said exhaust end, and is removed through said further tube, by gravity or by sucking, the exhaust end of the reaction tube being sealed by means of an inflatable elastomeric toroidal member placed between the internal surface of the reaction tube and the external surface of said further tube.

Claim 17

A method of doping a core of a silica-based fiber preform, comprising depositing a soot layer, which will form said core of said silica-based optical fiber preform, inside a reaction tube supported by a lathe, and connected to at least one deposition reactant inlet conduit and at least one exhaust conduit and then impregnating the deposited core soot layer contained inside said reaction tube supported by said lathe with a solution of a precursor of at least a first dopant which raises the refractive index of said layer without giving rise to a central dip of said index, said solution of a precursor of said first dopant being a solution in an anhydrous organic solvent, wherein after said layer deposition, (a) the reaction tube is disconnected from the at least one deposition reactant inlet conduit as well as from the at least one exhaust conduit for the deposition reaction volatile products; (b) at least a reaction product exhaust end of the reaction tube is sealed in a sealing operation, while an inert and anhydrous gas flow is maintained in said reaction tube during the sealing operation; (c) said solution is introduced into the reaction tube, without removing the tube from the lathe so that the solution covers the whole surface of the deposited layer and impregnation of the deposited layer occurs; and (d) once impregnation is over, the solution is caused to slowly flow out, at uniform rate, from the reaction tube, which reaction tube is still mounted on the lathe, the solution having been introduced after the reaction tube is disposed in an inclined position with an exhaust end down, via a further tube penetrating inside the reaction tube through said exhaust end, and said solution is removed through said further tube, by gravity or by sucking, the solution introduction and removal taking place, after sealing of opposite ends of the reaction tube, through a first radial branch of the reaction tube, said radial branch being connected to the reaction tube near one end of a deposition zone of the layer to be impregnated.

Claim 18

A method of doping a core of a silica-based fiber preform, comprising depositing a soot layer, which will form said core of said silica-based optical fiber preform, inside a reaction tube supported by a lathe, and connected to at least one deposition reactant inlet conduit and at least one exhaust conduit and then impregnating the deposited core soot layer contained inside said reaction tube supported by said lathe with a solution of a precursor of at least a first dopant which raises the refractive index of said layer without giving rise to a central dip of said index, said solution of a precursor of said first dopant being a solution in an anhydrous organic solvent, wherein after said layer deposition, (a) the reaction tube is disconnected from the at least one deposition reactant inlet conduit as well as from the at least one exhaust conduit for the deposition reaction volatile products; (b) at least a reaction product exhaust end of the reaction tube is sealed in a sealing operation, while an inert and anhydrous gas flow is maintained in said reaction tube during the sealing operation; (c) said solution is introduced into the reaction tube, without removing the tube from the lathe so that the solution covers the whole surface of the deposited layer and impregnation of the deposited layer occurs; and (d) once impregnation is over, the solution is caused to slowly flow out, at uniform rate, from the reaction tube, which reaction tube is still mounted on the lathe, the solution having been introduced after the reaction tube is disposed in an inclined position with an exhaust end down, via a further tube penetrating inside the reaction tube through said exhaust end, and said solution is removed through said further tube, by gravity or by sucking, the solution introduction and removal taking place, after sealing of opposite ends of the reaction tube, through a first radial branch of the reaction tube, said radial branch being connected to the reaction tube near one end of a deposition zone of the layer to be impregnated.