Prysmian S.p.a.

Prysmian Cavi E Sistemi Energia S.r.l.

Fibre Ottiche Sud - F.o.s. S.p.a.

Pirelli Cavi E Sistemi S.p.a.

Pirelli Limited

Franco Cocchini

Antonio Adigrat

Antonio Schiaffo

Antonio Collaro

Stefano Grieco

Valeria Caronna

Andrea Mazzotti

Alessandro Rossi

Giuseppe Ferri

Marco Antonio Caiata

Ida Nivelli

Antonio Faraldi

Mattheus Jacobus Nicolaas Van Stralen

Igor Milicevic

Enrico Maria Consonni

Marco Ruzzier

Antonello Schiaffo

Nicola Scafuro

Giuseppe Galasso

Cristiano Ruocchio

Francesco Di Matteo

Paolo Russo

Alfonso Cavallaro

Francesco Di Nola

Irene Di Giambattista

Arturo Ricco

Gertjan Krabshuis

Cedric Gonnet

Gerardo Testa

Andrea c/o Prysmian Cavi E Sistemi Telecom Srl Mazzotti

Giuseppe Malafronte

The present invention relates to a method for manufacturing a preform for optical fibers, which method comprises the sequential steps of: i) deposition of non-vitrified silica layers on the inner surface of a hollow substrate tube; ii) deposition of vitrified silica layers inside the hollow substrate tube on the inner surface of the non-vitrified silica layers deposited in step i); iii) removal of the hollow substrate tube from the vitrified silica layers deposited in step ii) and the non-vitrified silica layers deposited in step i) to obtain a deposited tube; iv) optional collapsing said deposited tube obtained in step iii) to obtain a deposited rod comprising from the periphery to the center at least one inner optical cladding and an optical core; v) preparation of an intermediate layer by the steps of: * deposition of non-vitrified silica layers on the outside surface of the deposited tube obtained in step iii) or deposited rod obtained in step iv) with a flame hydrolysis process in an outer reaction zone using glass-forming precursors, and subsequently; * drying and consolidating said non-vitrified silica layers into a vitrified fluorine-doped silica intermediate cladding layer; and * in case preceding step iv) was omitted collapsing; to provide a solid rod comprising from the periphery to the center the intermediate layer, at least one inner optical cladding and an optical core; wherein a fluorine-comprising gas is used during the deposition and/or drying and/or consolidating and wherein the intermediate layer has a ratio between the outer diameter of the intermediate cladding layer (C) to the outer diameter of the optical core (A) that is at least 3.5; vi) deposition of natural silica on the outside surface of the intermediate cladding layer of the solid rod obtained in step v) by melting natural silica particles in an outer deposition zone to produce an outer cladding whereby a preform is obtained.

Method for manufacturing a preform for optical fibers

Methods for manufacturing fluorine-doped glass preforms for optical fibers are disclosed. An exemplary method includes exposing a soot preform to an atmosphere containing a fluorine-containing gas in a first elongated chamber of a first furnace. The first elongated chamber typically has a single isothermal hot zone, which may be maintained at a doping temperature of about 800&#xb0; C. to 1200&#xb0; C., to obtain a fluorine-doped soot preform. The exemplary method further includes dehydrating the fluorine-doped soot preform by exposing it to an atmosphere containing a chlorine-containing gas in a second elongated chamber of a second furnace. The second elongated chamber typically has an upper hot zone, which may be maintained at a dehydration temperature of about 1000&#xb0; C. to 1350&#xb0; C., and a lower hot zone, which may be maintained at a consolidation temperature of about 1500&#xb0; C. to 1650&#xb0; C. Dehydration of the fluorine-doped soot preform typically occurs in the upper hot zone of the second furnace. The exemplary method further includes consolidating the fluorine-doped soot preform within the lower hot zone of the second furnace to form a fluorine-doped glass preform.

Method for manufacturing a glass preform for optical fibers

A method of manufacturing a glass core preform for optical fibres including providing a porous soot core preform having a central longitudinal hole extending axially therethrough and an a/b ratio of from 0.20 to 0.40; simultaneously dehydrating and doping with fluorine the soot core preform at a temperature of from 1000&#xb0; C. to 1350&#xb0; C. by exposing it to an atmosphere containing a chlorine-containing gas and a fluorine-containing gas, the content of the fluorine-containing gas in the atmosphere being of from 0.01% to 0.50% by volume, and simultaneously consolidating the soot core preform and closing the central longitudinal hole by exposing the soot core preform to an atmosphere substantially devoid of fluorine and of chlorine at a consolidation temperature of from 1500&#xb0; C. to 1650&#xb0; C., while reducing the pressure down the central hole, thereby forming a glass core preform.

Method for manufacturing a glass core preform for optical fibres

A method of manufacturing a glass core preform for an optical fibre comprising: providing a porous soot core preform having an outer surface) and a central hole extending axially therethrough; dehydrating the porous soot core preform at a first temperature by exposing the outer surface of the preform to an atmosphere containing chlorine, and simultaneously consolidating the soot core preform and closing the central hole at a second temperature higher than the first temperature to form a glass core preform, wherein consolidating and closing comprises sequentially alternating flowing chlorine containing gas into the central hole and reducing the internal pressure of the central hole.

Method of manufacturing preforms for optical fibres having low attenuation loss

Apparatus for applying traction to an elongate cylindrical element produced by fusion of an end portion of a preform of glass material, in which a traction device is capable of being connected to a portion of the elongate cylindrical element to provide traction of the elongate cylindrical element along an axis. A device for the rotation of the elongate cylindrical element applies a twist to the elongate cylindrical element about the axis simultaneously with the traction.

Plant for producing an elongate element usable for producing an optical fibre

A method for inspecting defects inside a rod-shaped transparent object by using a scanning beam of parallel light rays directed onto a rod-shaped transparent object orthogonally to the longitudinal axis of the object so that an inspection plane comprises an object's cross-section. The scanning beam is detected at an opposite side of the rod-shaped object that is interposed to intercept the parallel rays of the scanning beam. The electric output signal from the detector is processed to produce a first light intensity profile in a first scan direction, the light intensity profile comprising a shadow region delimited by first and second shadow edges, which is indicative of the outside diameter of the object across the inspection plane. The method comprises analyzing the first light intensity profile to determine the presence or absence of a peak of positive intensity within the shadow region and, if an intensity peak is determined to be present, to determine the presence or absence of a region of depressed intensity within the intensity peak. If, as a result of analyzing, an intensity peak within the shadow region is determined to be absent or a region of depressed intensity is determined to be present within the intensity peak, the presence of at least one structural defect within the object's cross-section is identified. In the preferred embodiments, the rod-shaped transparent object is a glass core rod for the production of a transmission optical fiber.

Method for detecting defects in a rod-shaped transparent object

A method of manufacturing at least one optical fibre preform comprising: providing a plurality of partially porous intermediate preforms, each partially porous intermediate preform having a longitudinal axis and comprising a respective soot intermediate clad layer formed around a respective glass core rod comprising a central core region of radius a and an inner clad region of radius b to define a first core-to-clad ratio a/b; consolidating the formed soot intermediate clad layers to form a respective plurality of intermediate glass preforms, each of the plurality of intermediate glass preforms comprising an intermediate clad region having an external radius c to define a second core-to-clad ratio a/c of from 0.20 to 0.30 , and overcladding at least one intermediate glass preform by forming an overclad region surrounding the intermediate clad region to form an optical fibre glass preform, wherein consolidating comprises exposing the plurality of intermediate preforms to a consolidation hot zone of a single furnace body while rotating each of the intermediate preforms about its respective longitudinal axis.

Method of manufacturing preforms for optical fibres having low water peak

A method of manufacturing an optical fibre preform comprising: providing a glass core rod comprising a central core region of radius a and an inner clad region of external radius b to define a first core-to-clad ratio a/b; forming an intermediate glass preform comprising an intermediate clad region surrounding the inner clad region of the glass rod and having an external radius c to define a second core-to-clad ratio a/c, and overcladding the intermediate glass preform by forming an overclad region surrounding the intermediate clad region to form an optical fibre preform, wherein the first core-to-clad ratio a/b is equal to or less than 0.40 and the second core-to-clad ratio a/c is of from 0.20 to 0.25.

A single-mode optical fiber for transmitting optical signals includes a central core region for guiding the optical signals, and a cladding region surrounding the core region and including a void-containing annular layer containing randomly distributed voids, wherein the void-containing layer is doped with fluorine at a concentration of less than 1 wt % and has a radial thickness equal to or smaller than 3 &#x3bc;m.

Bend-resistant single-mode optical fibre

An apparatus and method for chemical deposition on a rod member having a support structure for supporting the rod member substantially coaxial to a deposition axis; a burner for depositing chemical substances on the rod member; and a rotation device for imparting a rotation motion to the rod member. The rotation device has a joint member of a type suitable to transmit torque between two misaligned members, for example, a double universal joint or a flexible joint, positioned between a motor and a rod gripping member.

Apparatus and method for chemical deposition on a rod member in an optical fibre manufacturing process

Apparatus and method for applying traction to an elongate element produced by fusing a preform of glass material and usable in a process for producing an optical fibre

A process for manufacturing an optical fiber includes: drawing an optical waveguide from a glass preform; applying a layer of a first coating material on the optical waveguide; curing the first coating layer material to obtain a first coating layer; applying a layer of a second coating material onto the first coating layer; applying a layer of colored coating material onto the second coating layer; curing the second coating material and the colored coating material in a single step to obtain a second coating layer superposed on the first coating layer and a colored coating layer superposed on the second coating material layer, the obtained second coating layer having an elastic modulus higher than that of the first coating layer and lower than that of the colored coating layer. An optical fiber and an apparatus for producing it are also provided.

Process for manufacturing an optical fiber and an optical fiber so obtained

A process for manufacturing an optical fiber, includes the steps of: a) producing a soot core preform by depositing a core material on a substrate; b) removing the substrate from the soot preform leaving an axial cavity along the longitudinal axis of the soot core preform; (c) drying and consolidating the soot core preform so as to obtain a glass core preform having an axial hole corresponding to the axial cavity; d) reducing a diameter of the axial hole; and e) stretching the glass core preform so as to substantially close the axial hole, wherein the process further includes the step of measuring at least one geometric characteristic of the axial hole of the glass core preform.

Process for manufacturing a low-attenuation optical fiber

Telecommunication cable comprising at least one microstructured optical fiber comprising a core region and a cladding region surrounding the core region, the cladding region comprising an annular void-containing region comprised of randomly arranged voids, the core region including doped silica to provide a positive refractive index relative to pure silica; and at least one protecting layer provided around said optical fiber, the protecting layer being made of a polymeric material having a low ultimate elongation.

Telecommunication cable equipped with microstructured optical fibres

A manufacturing process of a microstructured optical fiber including a void-containing region, includes the steps of: drawing a microstructured optical fiber along a longitudinal direction from a heated preform, wherein the optical fiber is continuously advanced along the longitudinal direction; directing a radiation beam at a longitudinal position in the longitudinal direction of the optical fiber so as to produce an interference pattern; detecting the interference pattern and producing at least one electrical detection signal corresponding to the interference pattern and including a plurality of signal fringe cycles; feeding the first detection signal into a first counter circuit; determining a first number of interference fringe increments in the plurality of signal wave fringe cycles of the at least one detection signal by using the first counter circuit; determining the outer diameter of the optical fiber, and controlling the microstructure of the optical fiber during advancement of the optical fiber. The step of controlling includes at least one step selected from: (a) controlling the first number of interference fringe increments within a reference number range of reference numbers of interference fringe increments, and (b) calculating a microstructure length value.

Growing community of inventors

Salerno, Italy

Franco Cocchini