Optical fibers having a varying clad index and methods of forming same

Patent metadata

Field	Value
Publication number	US-10146008-B2
Application number	US-201715702961-A
Country	US
Kind code	B2
Filing date	Sep 13, 2017
Priority date	Sep 21, 2016
Publication date	Dec 4, 2018
Grant date	Dec 4, 2018

Abstract

An optical fiber with low attenuation and methods of making same are disclosed. The optical fiber has a core, an inner cladding surround the core, and an outer cladding surrounding the inner cladding. The outer cladding is chlorine-doped such that the relative refractive index varies as a function of radius. The radially varying relative refractive index profile of the outer cladding reduces excess stress in the core and inner cladding, which helps lower fiber attenuation while also reducing macrobend and microbend loss. A process of fabricating the optical fiber includes doping an overclad soot layer of a soot preform with chlorine and then removing a portion of the chlorine dopant from an outermost region of the overclad soot layer. The soot preform with the modified chlorine dopant profile is then sintered to form a glass preform, which can then be used for drawing the optical fiber.

First claim

What is claimed is:

1. An optical fiber comprising:
a core having an outer radius r 1 and a relative refractive index Δ 1 (r) having a maximum value Δ 1MAX , the core being centered on a central axis and having an alpha value greater than 1;
an inner cladding surrounding the core and having a relative refractive index Δ 2 and an outer radius r 2 greater than 9 microns;
an outer cladding immediately surrounding the inner cladding and having an outer radius r 3 and a relative refractive index Δ 3 (r) that includes at a radius r=r MAX , a maximum relative refractive index Δ 3MAX >Δ 2 , and that includes at a radius r=r MIN , a minimum relative refractive index Δ 3MIN , wherein r MIN >r MAX ;
wherein: i) Δ 1MAX >Δ 3MAX >Δ 2 ;
ii) Δ 3MAX −Δ 2 >0.005 Δ%;
iii) Δ 3MAX −Δ 3MIN ≥0.01 Δ%; and

wherein the outer cladding comprises chlorine doped silica with a chlorine concentration C that varies with the radial coordinate.

2. An optical fiber according to claim 1 , wherein the alpha value is less than 10.

3. An optical fiber according to claim 1 , wherein the chlorine concentration C has a maximum chlorine concentration C MAX at a radial coordinate r C _ MAX between r 2 and 40 microns and a minimum chlorine concentration C MIN at a radial coordinate r C _ MIN between r=40 microns and r 3 =62.5 microns, wherein C MAX is at least 1000 parts per million (ppm) greater than C MIN .

4. An optical fiber according to claim 3 , wherein C MAX is at least 1500 ppm greater than C MIN .

5. An optical fiber according to claim 4 , wherein C MAX is at least 2,000 ppm greater than C MIN .

6. An optical fiber according to claim 1 , further comprising an attenuation of less than 0.185 dB/km at a wavelength of 1550 nm.

7. An optical fiber according to claim 1 , further comprising a bend loss for a 20 mm diameter mandrel of less than 0.5 dB/turn at 1550 nm.

8. An optical fiber according to claim 1 , further comprising a zero dispersion wavelength λ 0 wherein 1300 nm≤λ 0 ≤1324 nm.

9. An optical fiber according to claim 1 , further comprising a mode-field diameter at a wavelength of 1310 nm of between 8.8 microns and 9.5 microns.

10. An optical fiber according to claim 1 , further comprising a cabled cutoff of less than or equal to 1260 nm.

11. An optical fiber according to claim 1 , wherein the inner cladding immediately surrounds the core.

Assignees

• Corning Inc

Inventors

• Bookbinder Dana Craig
• Chludzinski Paul Andrew
• Harper Brian Lee
• Li Ming-Jun
• Mishra Snigdharaj Kumar
• Raney Sonya Marie
• Tandon Pushkar

Classifications

• C03B2207/70

  Control measures · CPC title

• C03B37/01446

  Thermal after-treatment of preforms, e.g. dehydrating, consolidating, sintering (C03B37/01853 takes precedence) · CPC title

• C03B2201/08

  doped with boron or fluorine or other refractive index decreasing dopant · CPC title

• G02B6/0283

  Graded index region external to the central core segment, e.g. sloping layer or triangular or trapezoidal layer (G02B6/0288, G02B6/0286 take precedence) · CPC title

• G02B6/0286 Primary

  Combination of graded index in the central core segment and a graded index layer external to the central core segment (G02B6/0288 takes precedence) · CPC title