Optical fiber

Patent metadata

Field	Value
Publication number	US-9910216-B2
Application number	US-201715645303-A
Country	US
Kind code	B2
Filing date	Jul 10, 2017
Priority date	Jan 14, 2015
Publication date	Mar 6, 2018
Grant date	Mar 6, 2018

Abstract

One of embodiments relates to an optical fiber in which an alkali metal element is efficiently doped to its core to suppress transmission loss from increasing. A mean concentration or a concentration distribution of the alkali metal element is adjusted such that 0.48 or less is obtained as an weighted value obtained by weighting a distribution of field intensity of guided light at a wavelength of 1550 nm, with respect to a radial direction distribution of a ratio I D2 /I ω3 of an intensity I D2 of Raman scattering light by a silica three-membered ring structure and an intensity I ω3 of Raman scattering light by a Si—O stretching vibration, in a cross-sectional region having a diameter of 20 μm.

First claim

The invention claimed is:

1. An optical fiber mainly comprised of silica-based glass, comprising:
a core extending along an optical axis and including an alkali metal element; and
a cladding surrounding the core and having a refractive index lower than that of the core,
wherein, where an intensity of Raman scattering light ω 3 by a Si—O stretching vibration in a Raman scattering spectrum is I ω3 and an intensity of Raman scattering light D 2 by a silica three-membered ring structure is I D2 , a mean concentration of the alkali metal element in the core or a shape of a concentration distribution of the alkali metal element in the core is adjusted such that 0.48 or less is obtained as a weighted value of a distribution of a ratio I D2 /I ω3 along the radial direction of the optical fiber, the weighted value being obtained by weighting the distribution of the ratio I D2 /I ω3 with a distribution of field intensity along a radial direction of guided light at a wavelength of 1550 nm, calculated from a refractive index profile along the radial direction of the optical fiber, in a region including the optical axis as a center and having a diameter of 20 μm in a cross section of the optical fiber orthogonal to the optical axis.

2. The optical fiber according to claim 1 , wherein
the alkali metal element includes potassium.

3. The optical fiber according to claim 1 , wherein
the concentration distribution of the alkali metal element, in the cross section of the optical fiber orthogonal to the optical axis, has a shape in which a first concentration peak is located in an annular region surrounding the optical axis in a state in which the annular region is separated by a predetermined distance from the optical axis.

4. The optical fiber according to claim 3 , wherein
the concentration distribution of the alkali metal element, in the cross section of the optical fiber orthogonal to the optical axis, has a shape in which a second concentration peak, having a maximum concentration lower than a maximum concentration of the first concentration peak, is located in a region surrounded by the annular region.

5. The optical fiber according to claim 1 , wherein
the concentration distribution of the alkali metal element, in the cross section of the optical fiber orthogonal to the optical axis, has a shape in which there are a plurality of concentration peaks separated from each other along the radial direction of the optical fiber, and
a maximum concentration of one concentration peak close to the optical axis in two adjacent concentration peaks included in the plurality of concentration peaks is lower than a maximum concentration of the other concentration peak in the two adjacent concentration peaks.

6. An optical fiber mainly comprised of silica-based glass, comprising:
a core extending along an optical axis and including an alkali metal element; and
a cladding surrounding the core and having a refractive index lower than that of the core,
wherein, where an intensity of Raman scattering light ω 3 by a Si—O stretching vibration in a Raman scattering spectrum is I ω3 and an intensity of Raman scattering light D 2 by a silica three-membered ring structure is I D2 , a mean concentration of the alkali metal element in the core or a shape of a concentration distribution of the alkali metal element in the core is adjusted such that 0.50 or less is obtained as a ratio I D2 /I ω3 at a position where a field intensity of guided light at a wavelength of 1550 nm calculated from a refractive index profile along a radial direction of the optical fiber is maximized, in a cross section of the optical fiber orthogonal to the optical axis.

7. The optical fiber according to claim 6 , wherein
the alkali metal element includes potassium.

8. The optical fiber according to claim 6 , wherein
the concentration distribution of the alkali metal element, in the cross section of the optical fiber orthogonal to the optical axis, has a shape in which a first concentration peak is located in an annular region surrounding the optical axis in a state in which the annular region is separated by a predetermined distance from the optical axis.

9. The optical fiber according to claim 8 , wherein
the concentration distribution of the alkali metal element, in the cross section of the optical fiber orthogonal to the optical axis, has a shape in which a second concentration peak, having a maximum concentration lower than a maximum concentration of the first concentration peak, is located in a region surrounded by the annular region.

10. The optical fiber according to claim 6 , wherein
the concentration distribution of the alkali metal element, in the cross section of the optical fiber orthogonal to the optical axis, has a shape in which there are a plurality of concentration peaks separated from each other along the radial direction of the optical fiber, and
a maximum concentration of one concentration peak close to the optical axis in two adjacent concentration peaks included in the plurality of concentration peaks is lower than a maximum concentration of the other concentration peak in the two adjacent concentration peaks.

11. An optical fiber mainly comprised of silica-based glass, comprising:
a core extending along an optical axis and including an alkali metal element; and
a cladding surrounding the core and having a refractive index lower than that of the core,
wherein, where an intensity of Raman scattering light ω 3 by a Si—O stretching vibration in a Raman scattering spectrum is I ω3 and an intensity of Raman scattering light D 2 by a silica three-membered ring structure is I D2 , a mean concentration of the alkali metal element in the core or a shape of a concentration distribution of the alkali metal element in the core is adjusted such that 0.15 or less is obtained as a difference between a value of a ratio I D2 /I ω3 at a position where a field intensity of guided light at a wavelength of 1550 nm calculated from a refractive index profile along a radial direction of the optical fiber is maximized and a value of a ratio I D2 /I ω3 on the optical axis, in a cross section of the optical fiber orthogonal to the optical axis.

12. The optical fiber according to claim 11 , wherein
the alkali metal element includes potassium.

13. The optical fiber according to claim 11 , wherein
the concentration distribution of the alkali metal element, in the cross section of the optical fiber orthogonal to the optical axis, has a shape in which a first concentration peak is located in an annular region surrounding the optical axis in a state in which the annular region is separated by a predetermined distance from the optical axis.

14. The optical fiber according to claim 13 , wherein
the concentration distribution of the alkali metal element, in the cross section of the optical fiber orthogonal to the optical axis, has a shape in which a second concentration peak, having a maximum concentration lower than a maximum concentration of the first concentration peak, is located in a region surrounded by the annular region.

15. The optical fiber according to claim 11 , wherein
the concentration distribution of the alkali metal element, in the cross section of the optical fiber orthogonal to the optical axis, has a shape in which there are a plurality of concentration peaks separated from each other along the radial direction of the optical fiber, and
a maximum concentration of one concentration peak close to the optical axis in two adjacent concentration peaks included in the plurality of concentration peaks is lower than a maximum concentration of t

Assignees

• Sumitomo Electric Industries

Inventors

• Haruna Tetsuya
• Tamura Yoshiaki
• TUKUDA Yoshihiro

Classifications

• C03C2201/50

  containing alkali metals · CPC title

• C03C3/06 Primary

  with more than 90% silica by weight, e.g. quartz {(C03C3/045 takes precedence)} · CPC title

• C03B37/018

  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

• G02B6/03694 Primary

  Multiple layers differing in properties other than the refractive index, e.g. attenuation, diffusion, stress properties · CPC title

• C03C17/02

  with glass (C03C17/34, C03C17/44 take precedence) · CPC title