Single mode fibre with a trapezoid core, showing reduced losses

• US 10,295,733 B2
• Filed: 12/20/2013
• Issued: 05/21/2019
• Est. Priority Date: 12/20/2013
• Status: Active Grant

• Current Assignee: Draka-Comteq USA Incorporated (Draka-Comteq)
• Original Assignee: Draka-Comteq USA Incorporated (Draka-Comteq)
• Inventors: de Montmorillon, Louis-Anne, Sillard, Pierre
• Primary Examiner(s): Radowski, Peter
• Application Number:
  US15/105,767
• Publication Number:
  US 20170031089A1
• Time in Patent Office: 1,978 Days
• CPC Class Codes: G02B 6/0281 Graded index region forming part of the central core segment, e.g. alpha profile, triangular, trapezoidal core G02B6/0288, G02B6/0286 take precedence
• CPC Class Codes: G02B 6/03633 arranged - -
• CPC Class Codes: G02B 6/0365 arranged - - +

Abstract

The invention concerns a single mode optical fiber having a core and a cladding, the core refractive index profile having a trapezoid-like shape. According to an aspect of the invention, the transition part of the trapezoid-like core refractive index profile is obtained by gradually changing a concentration of at least two dopants from a concentration in said center part of said core to a concentration in a cladding part adjacent to said core.

Claims

1. A single mode optical fibre having a core surrounded by a cladding, the core refractive index profile having a trapezoid-like shape,

wherein said core comprises (i) a centre part having a radius r₀ and a refractive index no and (ii) a transition part ranging from radius r₀ to a radius r₁>

r₀, wherein r₁ is between 4.5 microns and 7.2 microns;

wherein a ratio r₀/r₁ of said centre part'"'"'s radius r₀ to said transition part'"'"'s radius r₁ is between 0.25 and 0.75;

wherein, to reduce Rayleigh scattering losses at a 1550 nm wavelength, said transition part of the trapezoid-like core refractive index profile is obtained by gradually changing a concentration of at least two dopants from a concentration in said centre part of said core to a concentration in a cladding part adjacent to said core;

wherein said centre part of said core comprises one or more dopants inducing refractive index higher than silica and wherein said one or more dopants induce a refractive index increase of 0.6×

10<sup>−

3</sup> or more, wherein the concentration of said one or more dopants inducing refractive index higher than silica decreases substantially linearly across said core'"'"'s transition part between radius r₀ and radius r₁; and

wherein said cladding comprises one or more dopants inducing refractive index lower than silica and wherein said one or more dopants induce a refractive index decrease of −

0.2×

10<sup>−

3</sup> or less, wherein the concentration of said one or more dopants inducing refractive index lower than silica changes substantially linearly across said core'"'"'s transition part between radius r₀ and radius r₁.

2. The single mode optical fibre of claim 1, wherein said cladding comprises at least one trench, a region of depressed refractive index.

3. The single mode optical fibre of claim 2,

wherein said cladding comprises:

an intermediate cladding ranging from radius r₁ to radius r₂>

r₁ and having a refractive index n₂;

said trench ranging from radius r₂ to radius r₃>

r₂ and having a refractive index n₃;

an outer cladding ranging from radius r₃ and having a refractive index n₄.

4. The single mode optical fibre of claim 3, wherein the ratio r₀/r₁ of said centre part of said core'"'"'s radius r₀ to said transition part'"'"'s radius r₁ is between 0.3 and 0.7.

5. The single mode optical fibre of claim 3, wherein said core has a surface integral V₀₁ of between about 19·

10<sup>−

3</sup> μ

m and 25·

10<sup>−

3</sup> μ

m, the surface integral being defined according to the following equation;

6. The single mode optical fibre of claim 3, wherein said trench has a surface integral V₀₃ of between about −

55·

10<sup>−

3</sup> μ

m and 0, the surface integral V₀₃ being defined according to the following equation

7. The single mode optical fibre of claim 3, wherein said core has a volume integral V₁₁ of between about 80·

10<sup>−

3</sup> μ

m² and 105·

10<sup>−

3</sup> μ

m², the volume integral V₁₁ being defined according to the following equation

8. The single mode optical fibre of claim 3, wherein said trench has a volume integral V₁₃ of between about −

1200·

10<sup>−

3</sup> μ

m² and 0, the volume integral V₁₃ being defined according to the following equation

9. The single mode optical fibre of claim 1, wherein said at least two dopants are selected from the group consisting of:

Germanium oxide;

Fluorine;

Phosphorus oxide; and

Boron oxide.

10. The single mode optical fibre of claim 1, wherein said optical fibre has a Mode Field Diameter between 8.6 μ

m and 9.5 μ

m at a 1310 nm wavelength and a maximum Cable Cut-Off Wavelength of 1260 nm.

11. A method of manufacturing the single mode optical fibre of claim 1, the core refractive index profile having a trapezoid-like shape, said method comprising a first step of Chemical Vapour Deposition to form a core-rod, followed by a second step of overcladding said core-rod to obtain a preform, followed by a third step of drawing an optical fibre from said preform,

wherein the first step of Chemical Vapour Deposition comprises a step of gradually changing a concentration of at least two dopants in said transition part from a concentration in said centre part of said core to a concentration in a cladding part adjacent to said core.

12. The method of claim 11, wherein said first step of Chemical Vapour Deposition including the step of gradually changing said concentration is carried out by introducing said dopants into a core-rod by means of a Furnace Chemical Vapour Deposition (FCVD) process or by means of a Plasma Chemical Vapour Deposition (PCVD) process.

13. Optical fibre transmission system comprising at least one single mode fibre according to claim 1.

14. The single mode optical fibre of claim 1, wherein:

said centre part of said core has a radius r₀ and a refractive index no of less than 6.0×

10<sup>−

3</sup>.

15. The single mode optical fibre of claim 1,

wherein the ratio r₀/r₁ of said centre part of said core'"'"'s radius r₀ to said transition part'"'"'s radius r₁ is between 0.3 and 0.7.

16. The single mode optical fibre of claim 1, wherein said single mode optical fibre has a zero dispersion wavelength between 1300 nm and 1324 nm.

17. The single mode optical fibre of claim 1, wherein the concentration of said one or more dopants inducing refractive index lower than silica increases substantially linearly across said core'"'"'s transition part between radius r₀ and radius r₁.

18. The single mode optical fibre of claim 1, wherein the concentration of said one or more dopants inducing refractive index lower than silica decreases substantially linearly across said core'"'"'s transition part between radius r₀ and radius r₁.

19. The single mode optical fibre of claim 1, wherein said one or more dopants inducing refractive index higher than silica consists essentially of Germanium oxide.

20. The single mode optical fibre of claim 1, wherein said one or more dopants inducing refractive index lower than silica consists essentially of Fluorine.