Low Loss Optical Fiber And Method Of Making The Same

Patent metadata

Field	Value
Publication number	US-2016109651-A1
Application number	US-201514825297-A
Country	US
Kind code	A1
Filing date	Aug 13, 2015
Priority date	Oct 21, 2014
Publication date	Apr 21, 2016
Grant date	—

Abstract

The core region of an optical fiber is doped with chlorine in a concentration that allows for the viscosity of the core region to be lowered, approaching the viscosity of the surrounding cladding. An annular interface region is disposed between the core and cladding and contains a concentration of fluorine dopant sufficient to match the viscosity of the core. By including this annular stress accommodation region, the cladding layer can be formed to include the relatively high concentration of fluorine required to provide the desired degree of optical signal confinement (Le., forming a “low loss” optical fiber).

First claim

What is claimed is:

1 . An optical fiber comprising
a chlorine-doped silica core region; a fluorine-doped cladding region; and a fluorine-doped annular stress-accommodation region disposed between the core region and the cladding region, the fluorine-doped annular stress-accommodation region including a concentration of a fluorine dopant sufficient to exhibit a viscosity similar to the core region, the cladding region exhibiting a fluorine dopant concentration greater than the annular stress accommodation region and at least sufficient to provide confinement of the propagating optical signal to the combination of the core region and the annular stress-accommodation region.

2 . The optical fiber of claim 1 wherein the core region includes a high concentration of Si—Cl bonds to provide a desired concentration of chlorine dopant.

3 . The optical fiber of claim 1 wherein the core region includes chlorine dopant provided by SiCl 4 .

4 . The optical fiber of claim 1 wherein the chlorine dopant concentration in the core region and the fluorine dopant in the annular stress-accommodation are determined such that the density of the core region essentially matches the density of the annular stress-accommodation region at a determined fictive temperature T f .

5 . The optical fiber of claim 4 wherein the fictive temperature T f is about 1600° C.

6 . The optical fiber of claim 4 wherein the optical fiber has an attenuation of less than about 0.33 dB/km at a wavelength of about 1385 nm.

7 . The optical fiber of claim 4 wherein the chlorine dopant concentration in the silica core region is between about 2000 ppm and 15,000 ppm by weight.

8 . The optical fiber of claim 4 wherein the fluorine dopant concentration in the annular stress-accommodation region is between about 0.3 mol % and 3.0mol %.

9 . The optical fiber of claim 4 wherein the chlorine dopant concentration in the silica core region is between about 2000 ppm and 15,000 ppm by weight and the fluorine dopant concentration in the annular stress-accommodation region is between about 0.3 mol % and 3.0 mol %.

10 . The optical fiber of claim 1 wherein the chlorine dopant concentration in the silica core region is between about 2000 ppm and 15,000 ppm by weight.

11 . The optical fiber of claim 1 wherein the fluorine dopant concentration in the annular stress-accommodation region is between about 0.3 mol % and 3.0 mol %.

12 . The optical fiber of claim 1 wherein the chlorine dopant concentration in the silica core region is between about 2000 ppm and 15,000 ppm by weight and the fluorine dopant concentration in the annular stress-accommodation region is between about 0.3 mol % and 3.0 mol %.

13 . The optical fiber of claim 1 wherein the silica core region is co-doped to include fluorine dopant in addition to the chlorine dopant.

14 . The optical fiber of claim 13 wherein the optical fiber has a group refractive index lower than the group refractive index value of pure silica.

15 . The optical fiber of claim 1 wherein the silica core region is substantially free of any germanium dopant.

16 . The optical fiber of claim 1 wherein the chlorine dopant concentration in the core region and the fluorine dopant in the annular stress-accommodation are determined such that the fraction of optical power present in the cladding region is less than 2%.

17 . The optical fiber of claim 1 wherein the optical fiber has an attenuation of less than about 0.175 dB/km at a propagating signal wavelength of about 1550 nm.

18 . The optical fiber of claim 1 wherein the optical fiber has an effective area of more than about 100 μm 2 at a wavelength of about 1550 nm.

19 . The optical fiber of claim 1 wherein the average residual stress is less than about 100 MPa in the core region and the annular stress-accommodation region.

20 . A method of fabricating an optical fiber from an optical fiber preform, the method comprising the steps of:
providing an optical fiber preform having a chlorine-doped silica core region, a fluorine-doped cladding region and an annular stress-accommodation region disposed between the core region and the cladding region, the annular stress-accommodation region including a concentration of a fluorine dopant sufficient to exhibit a viscosity similar to the core region, and the cladding region exhibiting a fluorine dopant concentration greater than the annular stress region; heating the provided preform to a predetermined draw temperature; and pulling the heated preform with a determined draw tension and a determined draw rate so as to draw down the optical preform into a desired final dimension of an optical fiber.

21 . The method as defined in claim 20 wherein the draw temperature is determined from the selected viscosity of the core and annular stress-accommodation regions.

22 . The method as defined in claim 21 wherein the draw temperature is in the range of 1800-2200° C.

23 . The method of claim 20 wherein the draw rate is greater than 3 m/s.

24 . The method of claim 20 wherein the draw rate is in the range of 3-40 m/s.

25 . The method of claim 20 wherein the draw tension is in the range of 25-250 gm, equivalent to a stress of between about 20 and 200 MPa in a 125 μm diameter optical fiber.

Assignees

• Ofs Fitel Llc

Inventors

• Borel Peter I
• Jensen Rasmus V S
• Levring Ole A
• Olsen Jorgen Ostgaard
• Peckham David W
• Trevor Dennis J
• Wisk Patrick W
• Yan Man F

Classifications

• C03B37/01869

  Collapsing · CPC title

• C03B2203/222

  Mismatching viscosities or softening points of glass layers · CPC title

• G02B6/03683 Primary

  arranged - - + + · CPC title

• C03B37/01453

  for doping the preform with flourine · CPC title

• G02B6/0365 Primary

  arranged - - + · CPC title