Abstract: A method of fabricating an optical fiber preform is disclosed which includes a step of outside deposition of silica possibly doped with at least one dopant by injecting at least one substance in the form of silica or a precursor of silica in the vicinity of a heating area created by a heating system during at least one pass of an injector system and the heating system along a longitudinal axis of the preform during which the relative positions of the injector and heating systems ore adjusted so that silica is deposited in the heated area regardless of the position of the heating system.

Abstract: Natural or synthetic silica is deposited on a preform set into rotation in front of a plasma torch which moves back and forth substantially parallel to a longitudinal direction of the preform, a first feed duct feeds the plasma with grains of natural or synthetic silica while a second feed duct feeds the plasma with a fluorine or chlorine compound, preferably a fluorine compound, mixed with a carrier gas. Any sodium or lithium contained in the grains of natural or synthetic silica react with the fluorine or chlorine of the fluorine or chlorine compound, thereby making it possible to improve the optical quality of fibers drawn from a preform built up with natural or synthetic silica, and to do so at reduced cost.

Abstract: A method of manufacturing a preform, the method comprising rotating a primary preform about an axis X, establishing relative displacement in translation between the preform and a plasma torch, and introducing a glass powder into the plasma flame, the glass powder being accelerated prior to penetrating into the plasma flame by an accelerator gas introduced into the flow of glass powder, said process being performed in an enclosure and said introduction being performed into an atmosphere at a regulated pressure lower than the pressure outside the enclosure. Apparatus for manufacturing the preform comprises an enclosure connected to a unit for regulating the pressure inside the enclosure.

Abstract: Natural or synthetic silica is deposited on a preform set into rotation in front of a plasma torch which moves back and forth substantially parallel to a longitudinal direction of the preform, a first feed duct feeds the plasma with grains of natural or synthetic silica while a second feed duct feeds the plasma with a fluorine or chlorine compound, preferably a fluorine compound, mixed with a carrier gas. Any sodium or lithium contained in the grains of natural or synthetic silica react with the fluorine or chlorine of the fluorine or chlorine compound, thereby making it possible to improve the optical quality of fibers drawn from a preform built up with natural or synthetic silica, and to do so at reduced cost.

Abstract: Natural or synthetic silica is deposited on a preform set into rotation in front of a plasma torch which moves back and forth substantially parallel to a longitudinal direction of the preform, a first feed duct feeds the plasma with grains of natural or synthetic silica while a second feed duct feeds the plasma with a fluorine or chlorine compound, preferably a fluorine compound, mixed with a carrier gas. Any sodium or lithium contained in the grains of natural or synthetic silica react with the fluorine or chlorine of the fluorine or chlorine compound, thereby making it possible to improve the optical quality of fibers drawn from a preform built up with natural or synthetic silica, and to do so at reduced cost.

Abstract: The method includes axially modulating at least one plasma build-up pass in order to improve the opto-geometrical properties of the preform. The modulation preferably takes place during the final passes of plasma build-up and takes place by modulating the build-up grain flow rate. The diameter of the preform is evaluated (6), and a build-up control device (8) regulates grain flow rate (11, 5) in application of the above method.

Abstract: The invention relates to manufacturing glass fiber preforms. It relates to a method comprising rotating preform about its own axis, and displacing a plasma torch in translation relative to the preform in a direction parallel to the axis of the preform, the axes of the flame and of the preform and being offset by a certain distance, and then inserting glass powder into the plasma flame under gravity. According to the invention, the glass powder is accelerated before penetrating into the plasma flame by means of an accelerator gas, and the offset distance between the axes is reduced with increasing acceleration of the powder. The invention is applicable to manufacturing glass fibers, and in particular optical fibers.

Abstract: A method of manufacturing a preform, the method comprising rotating a primary preform about an axis X, establishing relative displacement in translation between the preform and a plasma torch, and introducing a glass powder into the plasma flame, the glass powder being accelerated prior to penetrating into the plasma flame by an accelerator gas introduced into the flow of glass powder, said process being performed in an enclosure and said introduction being performed into an atmosphere at a regulated pressure lower than the pressure outside the enclosure. Apparatus for manufacturing the preform comprises an enclosure connected to a unit for regulating the pressure inside the enclosure.

Abstract: The deposit of natural or synthetic silica comprises a preform (1) set into rotation (7) in front of a plasma torch (3) which moves back and forth substantially parallel to a longitudinal direction (L) of the preform (1), a feed duct (9) for feeding the plasma with grains of natural or synthetic silica (11), characterized in that the same feed duct (9) feeds the plasma with a fluorine or chlorine compound, preferably a fluorine compound, mixed with a carrier gas (15). Sodium or lithium contained in the grains of natural or synthetic silica reacts with the fluorine or chlorine of the fluorine or chlorine compound, making it possible to improve the optical quality of fibers built up with the natural or synthetic silica at reduced cost.

Abstract: Natural or synthetic silica is deposited on a preform set into rotation in front of a plasma torch which moves back and forth substantially parallel to a longitudinal direction of the preform, a first feed duct feeds the plasma with grains of natural or synthetic silica while a second feed duct feeds the plasma with a fluorine or chlorine compound, preferably a fluorine compound, mixed with a carrier gas Any sodium or lithium contained in the grains of natural or synthetic silica react with the fluorine or chlorine of the fluorine or chlorine compound, thereby making it possible to improve the optical quality of fibers drawn from a preform built up with natural or synthetic silica, and to do so at reduced cost.

Abstract: The invention relates to manufacturing glass fiber preforms. It relates to a method comprising rotating preform about its own axis, and displacing a plasma torch in translation relative to the preform in a direction parallel to the axis of the preform, the axes of the flame and of the preform and being offset by a certain distance, and then inserting glass powder into the plasma flame under gravity. According to the invention, the glass powder is accelerated before penetrating into the plasma flame by means of an accelerator gas, and the offset distance between the axes is reduced with increasing acceleration of the powder. The invention is applicable to manufacturing glass fibers, and in particular optical fibers.

Abstract: A method of using a plasma to build up an optical fiber preform consists in injecting hydroxyl ions in a controlled manner into the build-up silica that is deposited on the preform. The invention is applicable to the manufacture of optical fibers, in particular monomode fibers.