Abstract: The present invention provides an installation for fabricating or overcladding an optical fiber preform, which installation includes an inductive torch for producing a plasma from a plasma generating gas and material feed means and is characterized in that said plasma generating gas is a mixture of a first gas chosen from diatomic gases and mixtures of at least two gases and argon in a proportion by volume from 0.5% to 10%.

Abstract: A probe for measuring electrical characteristics of an excitation current of a plasma is provided. The probe is mounted on a conductive line that includes an inner conductor and an outer conductor. The probe includes a current sensor and a voltage sensor. The current sensor includes a groove formed in the ground of one of the conductors in order to form a detour for the current flowing through the conductor, and a point for measuring electric voltage between a ground connected to the conductor and a point of the groove. The current sensor thus is able to measure a voltage proportional to the first time derivative of intensity (Iplasma) of the excitation current. The voltage sensor is a shunt sensor capable of measuring a voltage proportional to the first time derivative of the voltage (Vplasma) of the excitation current. A plasma reactor including a probe of the aforementioned type is also provided.

Abstract: A probe for measuring electrical characteristics of an excitation current of a plasma is provided. The probe is mounted on a conductive line that includes an inner conductor and an outer conductor. The probe includes a current sensor and a voltage sensor. The current sensor includes a grove formed in the ground of one of the conductors in order to form a detour for the current flowing through the conductor, and a point for measuring electric voltage between a ground connected to the conductor and a point of the groove. The current sensor thus is able to measure a voltage proportional to the first time derivative of intensity (Iplasma) of the excitation current. The voltage sensor is a shunt sensor capable of measuring a voltage proportional to the first time derivative of the voltage (Vplasma) of the excitation current. A plasma reactor including a probe of the aforementioned type is also provided.

Abstract: The present invention provides an installation for fabricating or overcladding an optical fiber preform, which installation includes an inductive torch for producing a plasma from a plasma generating gas and material feed means and is characterized in that said plasma generating gas is a mixture of a first gas chosen from diatomic gases and mixtures of at least two gases and argon in a proportion by volume from 0.5% to 10%.

Abstract: In an FCVD process for producing preforms for dispersion shifted optical fiber or dispersion compensating optical fiber having a core comprising a central portion, an inner cladding, a ring, and an outer cladding by depositing layers, the layers of the preform corresponding to the inner cladding and to the ring of the optical fiber have a phosphorus content not greater than 0.1 wt %.

Abstract: The method is designed to be implemented in an installation provided with means enabling a preform held between two points by supporting end-pieces to be rotated and to be moved in translation. Heater means for heating the preform by means of a plasma torch are associated with material supply means, so as to enable the preform to be manufactured in layers. Preform/torch relative displacements, with or without material being supplied, lead either to a new layer of material being deposited on the preform, or to the most recent layer deposited being glazed. Said method interposes a one-ended reduction in layer length, starting from one of the intermediate layers, while a succession of concentric layers are being deposited on the preform in a manner such that the lengths of the layers are progressively reduced so that the preform tapers towards it ends. The one-ended reduction leads to a limitation of the thickness of a determined segment at the level of the layer deposited immediately prior to the reduction.

Abstract: The invention relates to the field of processes for manufacturing optical fiber preforms. This is a process for manufacturing optical fiber preforms that includes a step of drawing the preform with a draw ratio that remains constant for the same preform and may vary from one preform to another depending on their respective mean diameters so as to reduce the variation in mean diameter between preforms or else a process for manufacturing optical fiber preforms that includes a step of compressing the preform with a compression ratio that remains constant for the same preform and may vary from one preform to another depending on their respective mean diameter so as to reduce the variation in mean diameter between preforms.

Abstract: A method of manufacturing an optical fiber preform (3) comprising: forming at least one silica-based outer deposition layer (23) by depositing silica on a primary preform (24) constituted by a bar mainly comprising silica and including a silica-based outer peripheral portion (22), the method being characterized in that the viscosity of the outer deposition layer (23) is adjusted to be substantially identical to the viscosity of the outer peripheral portion (22) of the primary preform (24) by adding to the silica, over a substantial portion of the outer deposition layer (23), at least one compound selected from the group formed by the following compounds: CaF2, MgF2, AlF3, B2O3, and Al2O3.

Abstract: A finger mechanism for controlling vertical displacement of a neutron-absorbing assembly in a nuclear reactor for power adjustment and emergency shut-down of the reactor comprises two hooks each having a body carrying pivotable fingers which are engageable in circular notches provided in a control bar which supports the neutron-absorbing assembly from its lower end. The hook bodies are movable vertically relative to the control bar in opposite directions to alternately engage and move the control bar vertically. The fingers are pivoted synchronously with movements of the hook bodies and movements of the hook bodies and fingers are controlled by rotatable cams driven by a common drive so that the control rod is displaced in a continuous movement during rotation of the cams.