Prysmian S.p.a.

Ricardo Antunes De Camargo

Lidia Terruzzi

Silvio Frigerio

A method of manufacturing an optical fiber preform includes: producing a core rod having a core rod diameter; inserting the core rod into a glass fluorine-doped intermediate cladding tube so as to form a core assembly, the intermediate cladding tube having an inner diameter and an outer diameter, wherein the inner diameter is larger than the core rod diameter, the radial difference between the inner diameter and the core rod diameter defining an annular gap; and applying a negative pressure inside the annular gap; and forming a core preform by heating the core assembly to collapse the intermediate cladding tube around the core rod while maintaining the negative pressure, wherein heating includes moving a heater outside the intermediate cladding tube and along an axial direction of the same, and forming an overcladding region surrounding the core preform so as to form an optical fiber preform.

Method of manufacturing an optical fibre glass preform

A single-mode transmission optical fiber includes a central core region radially outwardly from a centerline to a radius rand having a positive relative refractive index &#x394;; a first inner cladding region extending radially outwardly from the central core to a radius rand having a negative relative refractive index &#x394;; a second inner cladding region extending radially outwardly from the first inner cladding region to a radius rand having a non-negative relative refractive index &#x394;; an intermediate cladding region extending radially outwardly from the second inner cladding region to a radius rhaving a negative relative refractive index &#x394;larger in absolute value than the relative refractive index &#x394;; and an outer cladding region extending radially outwardly from the intermediate cladding region and having a non-negative relative refractive index &#x394;; wherein the relative refractive index &#x394;of the first inner cladding region is &#x2212;0.1&#xb7;10to &#x2212;1.0&#xb7;10and the relative refractive index &#x394;of the intermediate cladding is &#x2212;3.0&#xb7;10to &#x2212;5.0&#xb7;10.

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Milan, Italy

Ricardo Antunes De Camargo