Optical fiber preform

Patent metadata

Field	Value
Publication number	US-10155687-B2
Application number	US-201615137255-A
Country	US
Kind code	B2
Filing date	Apr 25, 2016
Priority date	Apr 30, 2015
Publication date	Dec 18, 2018
Grant date	Dec 18, 2018

Abstract

An optical fiber preform of the present embodiment comprises a core portion and a cladding each comprised of silica glass. The core portion has a first dopant region including a central axis of the core portion and a second dopant region away from the central axis. The first dopant region contains a first dopant selected from among Na, K, and their compounds, and a concentration of the first dopant is 10 atomic ppm or more but 2,000 atomic ppm or less. The second dopant region contains a second dopant reducing viscosity of the silica glass. The second dopant has, as a characteristic at a temperature of 2,000° C. to 2,300° C., a diffusion coefficient of 1×10 −12 cm 2 /s or higher but lower than that of the first dopant, and a concentration of the second dopant region is 10 atomic ppm or more.

First claim

What is claimed is:

1. An optical fiber preform comprising:
a core portion comprised of silica glass and extending along a central axis thereof, in a cross-section of the optical fiber preform orthogonal to the central axis, the core portion having
a first dopant region containing a first dopant and including the central axis, the first dopant being selected from among Na, K, and their compounds, a concentration of the first dopant being set at 10 atomic ppm or more but 2,000 atomic ppm or less, and
a second dopant region containing a second dopant for reducing viscosity of the silica glass and surrounding the central axis while being away from the central axis, the second dopant having, as a characteristic at a temperature of 2,000° C. to 2,300° C., a diffusion coefficient of 1×10 −12 cm 2 /s or higher but lower than that of the first dopant, a concentration of the second dopant being set at 10 atomic ppm or more; and

a cladding portion comprised of silica glass and surrounding an outer periphery of the core portion, the cladding portion containing F and having a refractive index lower than that of the core portion.

2. The optical fiber preform according to claim 1 , wherein a ratio (r 2 /r 1 ) of a radius r 2 of the core portion to a distance r 1 from the central axis falls within a range from 3 to 9.5, the distance r 1 being defined as a distance from the central axis to a position where a concentration peak of the second dopant exists.

3. The optical fiber preform according to claim 1 , wherein the second dopant includes any one selected from among Rb, Cs, Mg, Ca, and Sr.

4. The optical fiber preform according to claim 2 , wherein the second dopant includes any one selected from among Rb, Cs, Mg, Ca, and Sr.

5. The optical fiber preform according to claim 1 , wherein, in the cross-section, the first and second dopant regions overlap each other.

6. The optical fiber preform according to claim 1 , wherein, in the cross-section, an outer periphery of the first dopant region is away from or corresponds to an inner periphery of the second dopant region.

Assignees

• Sumitomo Electric Industries

Inventors

• Tamura Yoshiaki
• Haruna Tetsuya
• Kawaguchi Yuki

Classifications

• C03C2201/54

  containing beryllium, magnesium or alkaline earth metals · CPC title

• C03B37/01861

  Means for changing or stabilising the diameter or form of tubes or rods · CPC title

• C03B2203/22

  Radial profile of refractive index, composition or softening point · CPC title

• C03B2201/50

  doped with alkali metals · CPC title

• C03C2201/50

  containing alkali metals · CPC title