Abstract: The invention relates to a method of fabricating an optical fiber with improved control of transmission characteristics. It proposes determining variations in the characteristics of the preform departing from the design characteristics and modifying the diameter of the fiber during drawing as a function of the measured variations. By varying the diameter of the fiber, variations in the preform departing from its design values can be compensated, in other words irregularities of the preform can be smoothed out. This variation limits the effect of preform variations on the propagation characteristics of the fiber.

Abstract: The invention relates to a method of fabricating an optical fiber with improved control of transmission characteristics. It proposes determining variations in the characteristics of the preform departing from the design characteristics and modifying the diameter of the fiber during drawing as a function of the measured variations. By varying the diameter of the fiber, variations in the preform departing from its design values can be compensated, in other words irregularities of the preform can be smoothed out. This variation limits the effect of preform variations on the propagation characteristics of the fiber.

Abstract: A method and apparatus for manufacturing optical fibers provided with hermetic coatings, wherein the bare fiber made from a heated preform advances through a stream of reactive gaseous medium which flows at a constant speed in the direction of advance of the fiber, which is then accelerated, and which is finally removed remote from the fiber by a stream of inert gas flowing in the opposite direction from the direction of the stream of reactive gaseous medium. Application is to manufacturing optical fibers for telecommunications.

Abstract: The invention relates to a method of coating an optical fiber, the method comprising the following steps: applying a polymerizable coating material to the surface of the optical fiber; and polymerizing said material to obtain a coating. In the method, the optical fiber prior to application of said material is raised to a value T determining the value T' of the temperature at which said material polymerizes.

Abstract: A device for drawing down an optical fiber preform (2) connected at one end to a feed rod (3) having an equal or smaller diameter. A chamber (11) in which the preform is drawn has an upper part (11A) with an opening (12). The opening engages the preform to seal the chamber. An enclosure (5) has a seal (6) at its upper part (5A) for sealing around the feed rod. A lower part (5B) of the enclosure contacts the upper part of the chamber to seal the chamber while the feed rod is passing through the opening.

Abstract: The present invention relates to a method of detecting whether at least one die is centered about a thread held taught between two fixed points separated by a distance L, wherein:the thread is excited into vibration;its frequency F of vibration is measured;the corresponding length 1 of vibrating chord between one of said fixed points referred to as a "reference" fixed point and another point referred to as a "contact" point is deduced therefrom; andlength l is compared with length L and with the length of the segment of thread between said reference fixed point and said die, so as to deduce therefrom:either that the thread is touching said die, if length l corresponds to the length of the segment, said contact point then being situated at said die;or else that the thread is not touching said die, if length l is equal to the length L between said two fixed points, in which case said die is properly centered, said contact point then coinciding with the other one of said fixed points.

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.