Optical fiber preform and method for manufacturing such optical fiber preform from a primary preform

Patent metadata

Field	Value
Publication number	US-2016185649-A1
Application number	US-201314911522-A
Country	US
Kind code	A1
Filing date	Aug 13, 2013
Priority date	Aug 13, 2013
Publication date	Jun 30, 2016
Grant date	—

Abstract

The invention relates to an optical fiber preform ( 20 ) comprising a primary preform ( 21 ) and one or more purified silica-based overclad layers ( 22 ) surrounding said primary preform ( 21 ), the purified silica-based overclad layers ( 22 ) comprising lithium and aluminium, and having a ratio between lithium concentration [Li] and aluminium concentration [Al] satisfying the following inequality (Formula (I)).
1.10 3 ≦ [Li] / [Al] ≦20.10 3   (1)

First claim

1 . An optical fiber preform comprising a primary preform and at least one purified silica-based overclad layer surrounding the primary preform, the at least one purified silica-based overclad layer comprising lithium and aluminium, wherein the at least one purified silica-based overclad layer has a ratio between lithium concentration [Li] and aluminium concentration [Al] satisfying the following inequality:
1.10 −3 ≦ [Li] / [Al] ≦20.10 −3

2 . The optical fiber preform according to claim 1 , wherein the ratio between lithium concentration [Li] and aluminium concentration [Al] satisfies the following inequality:
4.10 −3 ≦ [Li] / [Al] ≦10.10 −3

3 . The optical fiber preform according to claim 1 , wherein the ratio between lithium concentration [Li] and aluminium concentration [Al] satisfies the following inequality:
4.10 −3 ≦ [Li] / [Al] ≦6.10 −3

4 . An optical fiber made from the optical fiber preform according to claim 1 .

5 . A method for manufacturing an optical fiber preform from a primary preform, comprising the steps of:
depositing at least one silica-based overclad layer on the primary preform by injection of a powder of natural silica into a plasma provided by a plasma source, injecting, into the plasma, a purifying gas intended to react with lithium, and adjusting at least one purifying gas injection parameter such that the at least one silica-based overclad layer deposited on the primary preform has a ratio between lithium concentration [Li] and aluminium concentration [Al] satisfying the following inequality:
1.10 −3 ≦ [Li] / [Al] ≦20.10 −3

6 . The method according to claim 5 , wherein the ratio between lithium concentration [Li] and aluminium concentration [Al] satisfies the following inequality:
4.10 −3 ≦ [Li] / [Al] ≦10.10 −3

7 . The method according to claim 5 , wherein the ratio between lithium concentration [Li] and aluminium concentration [Al] satisfies the following inequality:
4.10 −3 ≦ [Li] / [Al] ≦6.10 −3

8 . The method according to claim 5 , wherein the method further comprises a step of controlling lithium concentration [Li] and aluminium concentration [Al] in the at least one silica-based overclad layer deposited on the primary preform, and wherein the step of adjusting at least one purifying gas injection parameter is carried out as a function of the result of the controlling step.

9 . The method according to claim 8 , wherein the method further comprises a step of injecting in the plasma a quantity of lithium adjusted as a function of the result of the controlling step.

10 . The method according to claim 8 , wherein the method further comprises a step of injecting in the plasma a quantity of aluminum adjusted as a function of the result of the controlling step.

11 . The method according to claim 5 , wherein the at least one purifying gas injection parameter comprises a purifying gas flow rate.

12 . The method according to claim 11 , wherein the purifying gas flow rate is set between 0 and 5000 sccm.

13 . The method according to claim 5 , wherein the purifying gas selected from the group comprising: SF 6 , C 2 F 6 , Cl 2 , CF 4 , NF 3 , CF 3 CI, C 2 Cl 3 CF 3 .

14 . The method according to claim 11 , wherein the purifying gas flow rate is set between 8 and 800 sccm.

Assignees

• Draka Comteq Bv

Inventors

• Gonnet Cédric
• Petitfrere Emmanuel
• Calvo Laurent
• Delwal Olivier

Classifications

• C03B2201/03

  Impurity concentration specified · CPC title

• C03B2201/32

  doped with aluminium (C03B2201/36 takes precedence) · CPC title

• C03C2201/02

  Pure silica glass, e.g. pure fused quartz · CPC title

• C03B37/018 Primary

  by glass deposition on a glass substrate, e.g. by {inside-, modified-, plasma- or plasma modified-} chemical vapour deposition {[ICVD, MCVD, PCVD, PMCVD], i.e. by thin layer coating on the inside or outside of a glass tube or on a glass rod} (C03B37/016 takes precedence; surface treatment of glass by coating with glass C03C17/02) · CPC title

• C03B2201/50

  doped with alkali metals · CPC title